[RFC 00/17] dma-fence lockdep annotations

[RFC 00/17] dma-fence lockdep annotations

[Daniel Vetter]

Hi all,

I've dragged my feet for years on this, hoping that cross-release lockdep
would do this for us, but well that never really happened unfortunately.
So here we are.

Cc'ed quite a pile of people since this is about the cross-driver contract
around dma_fences. Which is heavily used for dma_buf, and I'm hearing more
noises that rdma folks are looking into this, hence also on cc.

There's a bunch of different parts to this RFC:

- The annotations itself, in the 2nd patch after the prep patch to add
  might_sleep annotations. Commit message has all the motivation for what
  kind of deadlocks I want to catch, best you just read it.

  Since lockdep doesn't understand cross-release natively we need to
  cobble something together using rwlocks and a few more tricks, but from
  the test rollout in a few places in drm/vkms, amdgpu & i915 I think what
  I have now seems to actually work. Downside is that we have to
  explicitly annotate all code involved in eventual dma_fence signalling.

- Second important part is locking down the current dma-fence cross-driver
  contract, using lockdep priming like we already do for dma_resv_lock.
  I've just started with my own take on what we probably need to make the
  current code work (-ish), but both amdgpu and i915 have issues with
  that. So this needs some careful discussions, and also some thought on
  how we land it all eventually to not break lockdep completely for
  everyone.

  The important patch for that is "dma-fence: prime lockdep annotations"
  plus of course the various annotations patches and driver hacks to
  highlight some of the issues caught.

  Note that depending upon what exactly we end up deciding we might need
  to improve the annotations for fs_reclaim_acquire/release - for
  dma_fence_wait in mmu notifiers we can only allow GFP_NOWAIT (afaiui),
  and currently fs_reclaim_acquire/release only has a lockdep class for
  __GFP_FS only, we'd need to add another one for __GFP_DIRECT_RECLAIM in
  general maybe.

- Finally there's clearly some gaps in the current dma_fence driver
  interfaces: Amdgpu's hang recovery is essentially impossible to fix
  as-is - it needs to reset the display state and you can't get at modeset
  locks from tdr without deadlock potential. i915 has an internal trick
  (but it stops working once we involve real cross-driver fences) for this
  issues, but then for i915 modeset reset is only needed on very ancient
  gen2/3. Modern hw is a lot more reasonable.

  I'm kinda hoping that the annotations and priming for basic command
  submission and atomic modeset paths could be merged soonish, while we
  the tdr side clearly needs a pile more work to get going. But since we
  have to explicitly annotate all code paths anyway we can hide bugs in
  e.g. tdr code by simply not yet annotating those functions.

  I'm trying to lay out at least one idea for solving the tdr issue in the
  patch titled "drm/scheduler: use dma-fence annotations in tdr work".

Finally, once we have some agreement on where we're going with all this,
we also need some documentation. Currently that's missing because I don't
want to re-edit the text all the time while we still figure out the
details of the exact cross-driver semantics.

My goal here is that with this we can lock down the cross-driver contract
for the last bit of the dma_buf/resv/fence story and make sure this stops
being such a wobbly thing where everyone just does whatever they feel
like.

Ideas, thoughts, reviews, testing (with specific annotations for that
driver) on other drivers very much welcome.

Cheers, Daniel

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>

Daniel Vetter (17):
  dma-fence: add might_sleep annotation to _wait()
  dma-fence: basic lockdep annotations
  dma-fence: prime lockdep annotations
  drm/vkms: Annotate vblank timer
  drm/vblank: Annotate with dma-fence signalling section
  drm/atomic-helper: Add dma-fence annotations
  drm/amdgpu: add dma-fence annotations to atomic commit path
  drm/scheduler: use dma-fence annotations in main thread
  drm/amdgpu: use dma-fence annotations in cs_submit()
  drm/amdgpu: s/GFP_KERNEL/GFP_ATOMIC in scheduler code
  drm/amdgpu: DC also loves to allocate stuff where it shouldn't
  drm/amdgpu/dc: Stop dma_resv_lock inversion in commit_tail
  drm/scheduler: use dma-fence annotations in tdr work
  drm/amdgpu: use dma-fence annotations for gpu reset code
  Revert "drm/amdgpu: add fbdev suspend/resume on gpu reset"
  drm/amdgpu: gpu recovery does full modesets
  drm/i915: Annotate dma_fence_work

 drivers/dma-buf/dma-fence.c                   | 56 +++++++++++++++++++
 drivers/dma-buf/dma-resv.c                    |  1 +
 drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c        |  5 ++
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c    | 22 ++++++--
 drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c     |  2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c       |  2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c      |  2 +-
 drivers/gpu/drm/amd/amdgpu/atom.c             |  2 +-
 .../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 18 +++++-
 drivers/gpu/drm/amd/display/dc/core/dc.c      |  4 +-
 drivers/gpu/drm/drm_atomic_helper.c           | 16 ++++++
 drivers/gpu/drm/drm_vblank.c                  |  8 ++-
 drivers/gpu/drm/i915/i915_sw_fence_work.c     |  3 +
 drivers/gpu/drm/scheduler/sched_main.c        | 11 ++++
 drivers/gpu/drm/vkms/vkms_crtc.c              |  8 ++-
 include/linux/dma-fence.h                     | 13 +++++
 16 files changed, 160 insertions(+), 13 deletions(-)

-- 
2.26.2

[RFC 01/17] dma-fence: add might_sleep annotation to _wait()

[Daniel Vetter]

But only for non-zero timeout, to avoid false positives.

One question here is whether the might_sleep should be unconditional,
or only for real timeouts. I'm not sure, so went with the more
defensive option. But in the interest of locking down the cross-driver
dma_fence rules we might want to be more aggressive.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/dma-buf/dma-fence.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 052a41e2451c..6802125349fb 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -208,6 +208,9 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
 	if (WARN_ON(timeout < 0))
 		return -EINVAL;
 
+	if (timeout > 0)
+		might_sleep();
+
 	trace_dma_fence_wait_start(fence);
 	if (fence->ops->wait)
 		ret = fence->ops->wait(fence, intr, timeout);
-- 
2.26.2

[RFC 02/17] dma-fence: basic lockdep annotations

[Daniel Vetter]

Design is similar to the lockdep annotations for workers, but with
some twists:

- We use a read-lock for the execution/worker/completion side, so that
  this explicit annotation can be more liberally sprinkled around.
  With read locks lockdep isn't going to complain if the read-side
  isn't nested the same way under all circumstances, so ABBA deadlocks
  are ok. Which they are, since this is an annotation only.

- We're using non-recursive lockdep read lock mode, since in recursive
  read lock mode lockdep does not catch read side hazards. And we
  _very_ much want read side hazards to be caught. For full details of
  this limitation see

  commit e91498589746065e3ae95d9a00b068e525eec34f
  Author: Peter Zijlstra <peterz@infradead.org>
  Date:   Wed Aug 23 13:13:11 2017 +0200

      locking/lockdep/selftests: Add mixed read-write ABBA tests

- To allow nesting of the read-side explicit annotations we explicitly
  keep track of the nesting. lock_is_held() allows us to do that.

- The wait-side annotation is a write lock, and entirely done within
  dma_fence_wait() for everyone by default.

- To be able to freely annotate helper functions I want to make it ok
  to call dma_fence_begin/end_signalling from soft/hardirq context.
  First attempt was using the hardirq locking context for the write
  side in lockdep, but this forces all normal spinlocks nested within
  dma_fence_begin/end_signalling to be spinlocks. That bollocks.

  The approach now is to simple check in_atomic(), and for these cases
  entirely rely on the might_sleep() check in dma_fence_wait(). That
  will catch any wrong nesting against spinlocks from soft/hardirq
  contexts.

The idea here is that every code path that's critical for eventually
signalling a dma_fence should be annotated with
dma_fence_begin/end_signalling. The annotation ideally starts right
after a dma_fence is published (added to a dma_resv, exposed as a
sync_file fd, attached to a drm_syncobj fd, or anything else that
makes the dma_fence visible to other kernel threads), up to and
including the dma_fence_wait(). Examples are irq handlers, the
scheduler rt threads, the tail of execbuf (after the corresponding
fences are visible), any workers that end up signalling dma_fences and
really anything else. Not annotated should be code paths that only
complete fences opportunistically as the gpu progresses, like e.g.
shrinker/eviction code.

The main class of deadlocks this is supposed to catch are:

Thread A:

	mutex_lock(A);
	mutex_unlock(A);

	dma_fence_signal();

Thread B:

	mutex_lock(A);
	dma_fence_wait();
	mutex_unlock(A);

Thread B is blocked on A signalling the fence, but A never gets around
to that because it cannot acquire the lock A.

Note that dma_fence_wait() is allowed to be nested within
dma_fence_begin/end_signalling sections. To allow this to happen the
read lock needs to be upgraded to a write lock, which means that any
other lock is acquired between the dma_fence_begin_signalling() call and
the call to dma_fence_wait(), and still held, this will result in an
immediate lockdep complaint. The only other option would be to not
annotate such calls, defeating the point. Therefore these annotations
cannot be sprinkled over the code entirely mindless to avoid false
positives.

v2: handle soft/hardirq ctx better against write side and dont forget
EXPORT_SYMBOL, drivers can't use this otherwise.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/dma-buf/dma-fence.c | 53 +++++++++++++++++++++++++++++++++++++
 include/linux/dma-fence.h   | 12 +++++++++
 2 files changed, 65 insertions(+)

diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
index 6802125349fb..d5c0fd2efc70 100644
--- a/drivers/dma-buf/dma-fence.c
+++ b/drivers/dma-buf/dma-fence.c
@@ -110,6 +110,52 @@ u64 dma_fence_context_alloc(unsigned num)
 }
 EXPORT_SYMBOL(dma_fence_context_alloc);
 
+#ifdef CONFIG_LOCKDEP
+struct lockdep_map	dma_fence_lockdep_map = {
+	.name = "dma_fence_map"
+};
+
+bool dma_fence_begin_signalling(void)
+{
+	/* explicitly nesting ... */
+	if (lock_is_held_type(&dma_fence_lockdep_map, 1))
+		return true;
+
+	/* rely on might_sleep check for soft/hardirq locks */
+	if (in_atomic())
+		return true;
+
+	/* ... and non-recursive readlock */
+	lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _RET_IP_);
+
+	return false;
+}
+EXPORT_SYMBOL(dma_fence_begin_signalling);
+
+void dma_fence_end_signalling(bool cookie)
+{
+	if (cookie)
+		return;
+
+	lock_release(&dma_fence_lockdep_map, _RET_IP_);
+}
+EXPORT_SYMBOL(dma_fence_end_signalling);
+
+void __dma_fence_might_wait(void)
+{
+	bool tmp;
+
+	tmp = lock_is_held_type(&dma_fence_lockdep_map, 1);
+	if (tmp)
+		lock_release(&dma_fence_lockdep_map, _THIS_IP_);
+	lock_map_acquire(&dma_fence_lockdep_map);
+	lock_map_release(&dma_fence_lockdep_map);
+	if (tmp)
+		lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _THIS_IP_);
+}
+#endif
+
+
 /**
  * dma_fence_signal_locked - signal completion of a fence
  * @fence: the fence to signal
@@ -170,14 +216,19 @@ int dma_fence_signal(struct dma_fence *fence)
 {
 	unsigned long flags;
 	int ret;
+	bool tmp;
 
 	if (!fence)
 		return -EINVAL;
 
+	tmp = dma_fence_begin_signalling();
+
 	spin_lock_irqsave(fence->lock, flags);
 	ret = dma_fence_signal_locked(fence);
 	spin_unlock_irqrestore(fence->lock, flags);
 
+	dma_fence_end_signalling(tmp);
+
 	return ret;
 }
 EXPORT_SYMBOL(dma_fence_signal);
@@ -211,6 +262,8 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
 	if (timeout > 0)
 		might_sleep();
 
+	__dma_fence_might_wait();
+
 	trace_dma_fence_wait_start(fence);
 	if (fence->ops->wait)
 		ret = fence->ops->wait(fence, intr, timeout);
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 3347c54f3a87..3f288f7db2ef 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -357,6 +357,18 @@ dma_fence_get_rcu_safe(struct dma_fence __rcu **fencep)
 	} while (1);
 }
 
+#ifdef CONFIG_LOCKDEP
+bool dma_fence_begin_signalling(void);
+void dma_fence_end_signalling(bool cookie);
+#else
+static inline bool dma_fence_begin_signalling(void)
+{
+	return true;
+}
+static inline void dma_fence_end_signalling(bool cookie) {}
+static inline void __dma_fence_might_wait(void) {}
+#endif
+
 int dma_fence_signal(struct dma_fence *fence);
 int dma_fence_signal_locked(struct dma_fence *fence);
 signed long dma_fence_default_wait(struct dma_fence *fence,
-- 
2.26.2

[RFC 03/17] dma-fence: prime lockdep annotations

[Daniel Vetter]

Two in one go:
- it is allowed to call dma_fence_wait() while holding a
  dma_resv_lock(). This is fundamental to how eviction works with ttm,
  so required.

- it is allowed to call dma_fence_wait() from memory reclaim contexts,
  specifically from shrinker callbacks (which i915 does), and from mmu
  notifier callbacks (which amdgpu does, and which i915 sometimes also
  does, and probably always should, but that's kinda a debate). Also
  for stuff like HMM we really need to be able to do this, or things
  get real dicey.

Consequence is that any critical path necessary to get to a
dma_fence_signal for a fence must never a) call dma_resv_lock nor b)
allocate memory with GFP_KERNEL. Also by implication of
dma_resv_lock(), no userspace faulting allowed. That's some supremely
obnoxious limitations, which is why we need to sprinkle the right
annotations to all relevant paths.

The one big locking context we're leaving out here is mmu notifiers,
added in

commit 23b68395c7c78a764e8963fc15a7cfd318bf187f
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Mon Aug 26 22:14:21 2019 +0200

    mm/mmu_notifiers: add a lockdep map for invalidate_range_start/end

that one covers a lot of other callsites, and it's also allowed to
wait on dma-fences from mmu notifiers. But there's no ready-made
functions exposed to prime this, so I've left it out for now.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/dma-buf/dma-resv.c | 1 +
 include/linux/dma-fence.h  | 1 +
 2 files changed, 2 insertions(+)

diff --git a/drivers/dma-buf/dma-resv.c b/drivers/dma-buf/dma-resv.c
index 99c0a33c918d..392c336f0732 100644
--- a/drivers/dma-buf/dma-resv.c
+++ b/drivers/dma-buf/dma-resv.c
@@ -115,6 +115,7 @@ static int __init dma_resv_lockdep(void)
 	if (ret == -EDEADLK)
 		dma_resv_lock_slow(&obj, &ctx);
 	fs_reclaim_acquire(GFP_KERNEL);
+	__dma_fence_might_wait();
 	fs_reclaim_release(GFP_KERNEL);
 	ww_mutex_unlock(&obj.lock);
 	ww_acquire_fini(&ctx);
diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
index 3f288f7db2ef..09e23adb351d 100644
--- a/include/linux/dma-fence.h
+++ b/include/linux/dma-fence.h
@@ -360,6 +360,7 @@ dma_fence_get_rcu_safe(struct dma_fence __rcu **fencep)
 #ifdef CONFIG_LOCKDEP
 bool dma_fence_begin_signalling(void);
 void dma_fence_end_signalling(bool cookie);
+void __dma_fence_might_wait(void);
 #else
 static inline bool dma_fence_begin_signalling(void)
 {
-- 
2.26.2

[RFC 04/17] drm/vkms: Annotate vblank timer

[Daniel Vetter]

This is needed to signal the fences from page flips, annotate it
accordingly. We need to annotate entire timer callback since if we get
stuck anywhere in there, then the timer stops, and hence fences stop.
Just annotating the top part that does the vblank handling isn't
enough.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Cc: Rodrigo Siqueira <rodrigosiqueiramelo@gmail.com>
Cc: Haneen Mohammed <hamohammed.sa@gmail.com>
Cc: Daniel Vetter <daniel@ffwll.ch>
---
 drivers/gpu/drm/vkms/vkms_crtc.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/vkms/vkms_crtc.c b/drivers/gpu/drm/vkms/vkms_crtc.c
index ac85e17428f8..a53a40848a72 100644
--- a/drivers/gpu/drm/vkms/vkms_crtc.c
+++ b/drivers/gpu/drm/vkms/vkms_crtc.c
@@ -1,5 +1,7 @@
 // SPDX-License-Identifier: GPL-2.0+
 
+#include <linux/dma-fence.h>
+
 #include <drm/drm_atomic.h>
 #include <drm/drm_atomic_helper.h>
 #include <drm/drm_probe_helper.h>
@@ -14,7 +16,9 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
 	struct drm_crtc *crtc = &output->crtc;
 	struct vkms_crtc_state *state;
 	u64 ret_overrun;
-	bool ret;
+	bool ret, fence_cookie;
+
+	fence_cookie = dma_fence_begin_signalling();
 
 	ret_overrun = hrtimer_forward_now(&output->vblank_hrtimer,
 					  output->period_ns);
@@ -49,6 +53,8 @@ static enum hrtimer_restart vkms_vblank_simulate(struct hrtimer *timer)
 			DRM_DEBUG_DRIVER("Composer worker already queued\n");
 	}
 
+	dma_fence_end_signalling(fence_cookie);
+
 	return HRTIMER_RESTART;
 }
 
-- 
2.26.2

[RFC 05/17] drm/vblank: Annotate with dma-fence signalling section

[Daniel Vetter]

This is rather overkill since currently all drivers call this from
hardirq (or at least timers). But maybe in the future we're going to
have thread irq handlers and what not, doesn't hurt to be prepared.
Plus this is an easy start for sprinkling these fence annotations into
shared code.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/drm_vblank.c | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 758bf74e1cab..125ef0c0f9a1 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -24,6 +24,7 @@
  * OTHER DEALINGS IN THE SOFTWARE.
  */
 
+#include <linux/dma-fence.h>
 #include <linux/export.h>
 #include <linux/moduleparam.h>
 
@@ -1895,7 +1896,7 @@ bool drm_handle_vblank(struct drm_device *dev, unsigned int pipe)
 {
 	struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
 	unsigned long irqflags;
-	bool disable_irq;
+	bool disable_irq, fence_cookie;
 
 	if (WARN_ON_ONCE(!dev->num_crtcs))
 		return false;
@@ -1903,6 +1904,8 @@ bool drm_handle_vblank(struct drm_device *dev, unsigned int pipe)
 	if (WARN_ON(pipe >= dev->num_crtcs))
 		return false;
 
+	fence_cookie = dma_fence_begin_signalling();
+
 	spin_lock_irqsave(&dev->event_lock, irqflags);
 
 	/* Need timestamp lock to prevent concurrent execution with
@@ -1915,6 +1918,7 @@ bool drm_handle_vblank(struct drm_device *dev, unsigned int pipe)
 	if (!vblank->enabled) {
 		spin_unlock(&dev->vblank_time_lock);
 		spin_unlock_irqrestore(&dev->event_lock, irqflags);
+		dma_fence_end_signalling(fence_cookie);
 		return false;
 	}
 
@@ -1940,6 +1944,8 @@ bool drm_handle_vblank(struct drm_device *dev, unsigned int pipe)
 	if (disable_irq)
 		vblank_disable_fn(&vblank->disable_timer);
 
+	dma_fence_end_signalling(fence_cookie);
+
 	return true;
 }
 EXPORT_SYMBOL(drm_handle_vblank);
-- 
2.26.2

[RFC 06/17] drm/atomic-helper: Add dma-fence annotations

[Daniel Vetter]

This is a bit disappointing since we need to split the annotations
over all the different parts.

I was considering just leaking the critical section into the
->atomic_commit_tail callback of each driver. But that would mean we
need to pass the fence_cookie into each driver (there's a total of 13
implementations of this hook right now), so bad flag day. And also a
bit leaky abstraction.

Hence just do it function-by-function.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/drm_atomic_helper.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/drivers/gpu/drm/drm_atomic_helper.c b/drivers/gpu/drm/drm_atomic_helper.c
index 8ac3aa068261..0a541368246e 100644
--- a/drivers/gpu/drm/drm_atomic_helper.c
+++ b/drivers/gpu/drm/drm_atomic_helper.c
@@ -1549,6 +1549,7 @@ EXPORT_SYMBOL(drm_atomic_helper_wait_for_flip_done);
 void drm_atomic_helper_commit_tail(struct drm_atomic_state *old_state)
 {
 	struct drm_device *dev = old_state->dev;
+	bool fence_cookie = dma_fence_begin_signalling();
 
 	drm_atomic_helper_commit_modeset_disables(dev, old_state);
 
@@ -1560,6 +1561,8 @@ void drm_atomic_helper_commit_tail(struct drm_atomic_state *old_state)
 
 	drm_atomic_helper_commit_hw_done(old_state);
 
+	dma_fence_end_signalling(fence_cookie);
+
 	drm_atomic_helper_wait_for_vblanks(dev, old_state);
 
 	drm_atomic_helper_cleanup_planes(dev, old_state);
@@ -1579,6 +1582,7 @@ EXPORT_SYMBOL(drm_atomic_helper_commit_tail);
 void drm_atomic_helper_commit_tail_rpm(struct drm_atomic_state *old_state)
 {
 	struct drm_device *dev = old_state->dev;
+	bool fence_cookie = dma_fence_begin_signalling();
 
 	drm_atomic_helper_commit_modeset_disables(dev, old_state);
 
@@ -1591,6 +1595,8 @@ void drm_atomic_helper_commit_tail_rpm(struct drm_atomic_state *old_state)
 
 	drm_atomic_helper_commit_hw_done(old_state);
 
+	dma_fence_end_signalling(fence_cookie);
+
 	drm_atomic_helper_wait_for_vblanks(dev, old_state);
 
 	drm_atomic_helper_cleanup_planes(dev, old_state);
@@ -1606,6 +1612,9 @@ static void commit_tail(struct drm_atomic_state *old_state)
 	ktime_t start;
 	s64 commit_time_ms;
 	unsigned int i, new_self_refresh_mask = 0;
+	bool fence_cookie;
+
+	fence_cookie = dma_fence_begin_signalling();
 
 	funcs = dev->mode_config.helper_private;
 
@@ -1634,6 +1643,8 @@ static void commit_tail(struct drm_atomic_state *old_state)
 		if (new_crtc_state->self_refresh_active)
 			new_self_refresh_mask |= BIT(i);
 
+	dma_fence_end_signalling(fence_cookie);
+
 	if (funcs && funcs->atomic_commit_tail)
 		funcs->atomic_commit_tail(old_state);
 	else
@@ -1789,6 +1800,7 @@ int drm_atomic_helper_commit(struct drm_device *dev,
 			     bool nonblock)
 {
 	int ret;
+	bool fence_cookie;
 
 	if (state->async_update) {
 		ret = drm_atomic_helper_prepare_planes(dev, state);
@@ -1811,6 +1823,8 @@ int drm_atomic_helper_commit(struct drm_device *dev,
 	if (ret)
 		return ret;
 
+	fence_cookie = dma_fence_begin_signalling();
+
 	if (!nonblock) {
 		ret = drm_atomic_helper_wait_for_fences(dev, state, true);
 		if (ret)
@@ -1848,6 +1862,7 @@ int drm_atomic_helper_commit(struct drm_device *dev,
 	 */
 
 	drm_atomic_state_get(state);
+	dma_fence_end_signalling(fence_cookie);
 	if (nonblock)
 		queue_work(system_unbound_wq, &state->commit_work);
 	else
@@ -1856,6 +1871,7 @@ int drm_atomic_helper_commit(struct drm_device *dev,
 	return 0;
 
 err:
+	dma_fence_end_signalling(fence_cookie);
 	drm_atomic_helper_cleanup_planes(dev, state);
 	return ret;
 }
-- 
2.26.2

[RFC 07/17] drm/amdgpu: add dma-fence annotations to atomic commit path

[Daniel Vetter]

I need a canary in a ttm-based atomic driver to make sure the
dma_fence_begin/end_signalling annotations actually work.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index ea0e039a667a..4469a8c96b08 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -57,6 +57,7 @@
 
 #include "ivsrcid/ivsrcid_vislands30.h"
 
+#include <linux/module.h>
 #include <linux/module.h>
 #include <linux/moduleparam.h>
 #include <linux/version.h>
@@ -7109,6 +7110,9 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 	struct drm_connector_state *old_con_state, *new_con_state;
 	struct dm_crtc_state *dm_old_crtc_state, *dm_new_crtc_state;
 	int crtc_disable_count = 0;
+	bool fence_cookie;
+
+	fence_cookie = dma_fence_begin_signalling();
 
 	drm_atomic_helper_update_legacy_modeset_state(dev, state);
 
@@ -7389,6 +7393,8 @@ static void amdgpu_dm_atomic_commit_tail(struct drm_atomic_state *state)
 	/* Signal HW programming completion */
 	drm_atomic_helper_commit_hw_done(state);
 
+	dma_fence_end_signalling(fence_cookie);
+
 	if (wait_for_vblank)
 		drm_atomic_helper_wait_for_flip_done(dev, state);
 
-- 
2.26.2

[RFC 08/17] drm/scheduler: use dma-fence annotations in main thread

[Daniel Vetter]

If the scheduler rt thread gets stuck on a mutex that we're holding
while waiting for gpu workloads to complete, we have a problem.

Add dma-fence annotations so that lockdep can check this for us.

I've tried to quite carefully review this, and I think it's at the
right spot. But obviosly no expert on drm scheduler.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/scheduler/sched_main.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 2f319102ae9f..06a736e506ad 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -763,9 +763,12 @@ static int drm_sched_main(void *param)
 	struct sched_param sparam = {.sched_priority = 1};
 	struct drm_gpu_scheduler *sched = (struct drm_gpu_scheduler *)param;
 	int r;
+	bool fence_cookie;
 
 	sched_setscheduler(current, SCHED_FIFO, &sparam);
 
+	fence_cookie = dma_fence_begin_signalling();
+
 	while (!kthread_should_stop()) {
 		struct drm_sched_entity *entity = NULL;
 		struct drm_sched_fence *s_fence;
@@ -823,6 +826,9 @@ static int drm_sched_main(void *param)
 
 		wake_up(&sched->job_scheduled);
 	}
+
+	dma_fence_end_signalling(fence_cookie);
+
 	return 0;
 }
 
-- 
2.26.2

[RFC 09/17] drm/amdgpu: use dma-fence annotations in cs_submit()

[Daniel Vetter]

This is a bit tricky, since ->notifier_lock is held while calling
dma_fence_wait we must ensure that also the read side (i.e.
dma_fence_begin_signalling) is on the same side. If we mix this up
lockdep complaints, and that's again why we want to have these
annotations.

A nice side effect of this is that because of the fs_reclaim priming
for dma_fence_enable lockdep now automatically checks for us that
nothing in here allocates memory, without even running any userptr
workloads.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
index 7653f62b1b2d..6db3f3c629b0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
@@ -1213,6 +1213,7 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
 	struct amdgpu_job *job;
 	uint64_t seq;
 	int r;
+	bool fence_cookie;
 
 	job = p->job;
 	p->job = NULL;
@@ -1227,6 +1228,8 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
 	 */
 	mutex_lock(&p->adev->notifier_lock);
 
+	fence_cookie = dma_fence_begin_signalling();
+
 	/* If userptr are invalidated after amdgpu_cs_parser_bos(), return
 	 * -EAGAIN, drmIoctl in libdrm will restart the amdgpu_cs_ioctl.
 	 */
@@ -1264,12 +1267,14 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
 	amdgpu_vm_move_to_lru_tail(p->adev, &fpriv->vm);
 
 	ttm_eu_fence_buffer_objects(&p->ticket, &p->validated, p->fence);
+	dma_fence_end_signalling(fence_cookie);
 	mutex_unlock(&p->adev->notifier_lock);
 
 	return 0;
 
 error_abort:
 	drm_sched_job_cleanup(&job->base);
+	dma_fence_end_signalling(fence_cookie);
 	mutex_unlock(&p->adev->notifier_lock);
 
 error_unlock:
-- 
2.26.2

[RFC 10/17] drm/amdgpu: s/GFP_KERNEL/GFP_ATOMIC in scheduler code

[Daniel Vetter]

My dma-fence lockdep annotations caught an inversion because we
allocate memory where we really shouldn't:

	kmem_cache_alloc+0x2b/0x6d0
	amdgpu_fence_emit+0x30/0x330 [amdgpu]
	amdgpu_ib_schedule+0x306/0x550 [amdgpu]
	amdgpu_job_run+0x10f/0x260 [amdgpu]
	drm_sched_main+0x1b9/0x490 [gpu_sched]
	kthread+0x12e/0x150

Trouble right now is that lockdep only validates against GFP_FS, which
would be good enough for shrinkers. But for mmu_notifiers we actually
need !GFP_ATOMIC, since they can be called from any page laundering,
even if GFP_NOFS or GFP_NOIO are set.

I guess we should improve the lockdep annotations for
fs_reclaim_acquire/release.

Ofc real fix is to properly preallocate this fence and stuff it into
the amdgpu job structure. But GFP_ATOMIC gets the lockdep splat out of
the way.

v2: Two more allocations in scheduler paths.

Frist one:

	__kmalloc+0x58/0x720
	amdgpu_vmid_grab+0x100/0xca0 [amdgpu]
	amdgpu_job_dependency+0xf9/0x120 [amdgpu]
	drm_sched_entity_pop_job+0x3f/0x440 [gpu_sched]
	drm_sched_main+0xf9/0x490 [gpu_sched]

Second one:

	kmem_cache_alloc+0x2b/0x6d0
	amdgpu_sync_fence+0x7e/0x110 [amdgpu]
	amdgpu_vmid_grab+0x86b/0xca0 [amdgpu]
	amdgpu_job_dependency+0xf9/0x120 [amdgpu]
	drm_sched_entity_pop_job+0x3f/0x440 [gpu_sched]
	drm_sched_main+0xf9/0x490 [gpu_sched]

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c   | 2 +-
 drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c  | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
index d878fe7fee51..055b47241bb1 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
@@ -143,7 +143,7 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f,
 	uint32_t seq;
 	int r;
 
-	fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_KERNEL);
+	fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_ATOMIC);
 	if (fence == NULL)
 		return -ENOMEM;
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
index fe92dcd94d4a..fdcd6659f5ad 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
@@ -208,7 +208,7 @@ static int amdgpu_vmid_grab_idle(struct amdgpu_vm *vm,
 	if (ring->vmid_wait && !dma_fence_is_signaled(ring->vmid_wait))
 		return amdgpu_sync_fence(sync, ring->vmid_wait, false);
 
-	fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_KERNEL);
+	fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_ATOMIC);
 	if (!fences)
 		return -ENOMEM;
 
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
index b87ca171986a..330476cc0c86 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
@@ -168,7 +168,7 @@ int amdgpu_sync_fence(struct amdgpu_sync *sync, struct dma_fence *f,
 	if (amdgpu_sync_add_later(sync, f, explicit))
 		return 0;
 
-	e = kmem_cache_alloc(amdgpu_sync_slab, GFP_KERNEL);
+	e = kmem_cache_alloc(amdgpu_sync_slab, GFP_ATOMIC);
 	if (!e)
 		return -ENOMEM;
 
-- 
2.26.2

[RFC 11/17] drm/amdgpu: DC also loves to allocate stuff where it shouldn't

[Daniel Vetter]

Not going to bother with a complete&pretty commit message, just
offending backtrace:

        kvmalloc_node+0x47/0x80
        dc_create_state+0x1f/0x60 [amdgpu]
        dc_commit_state+0xcb/0x9b0 [amdgpu]
        amdgpu_dm_atomic_commit_tail+0xd31/0x2010 [amdgpu]
        commit_tail+0xa4/0x140 [drm_kms_helper]
        drm_atomic_helper_commit+0x152/0x180 [drm_kms_helper]
        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
        drm_client_modeset_commit_locked+0x55/0x190 [drm]
        drm_client_modeset_commit+0x24/0x40 [drm]

v2: Found more in DC code, I'm just going to pile them all up.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/amd/amdgpu/atom.c                 | 2 +-
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 2 +-
 drivers/gpu/drm/amd/display/dc/core/dc.c          | 4 +++-
 3 files changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/atom.c b/drivers/gpu/drm/amd/amdgpu/atom.c
index 4cfc786699c7..1b0c674fab25 100644
--- a/drivers/gpu/drm/amd/amdgpu/atom.c
+++ b/drivers/gpu/drm/amd/amdgpu/atom.c
@@ -1226,7 +1226,7 @@ static int amdgpu_atom_execute_table_locked(struct atom_context *ctx, int index,
 	ectx.abort = false;
 	ectx.last_jump = 0;
 	if (ws)
-		ectx.ws = kcalloc(4, ws, GFP_KERNEL);
+		ectx.ws = kcalloc(4, ws, GFP_ATOMIC);
 	else
 		ectx.ws = NULL;
 
diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 4469a8c96b08..9bfaa4cad483 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6622,7 +6622,7 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
 		struct dc_stream_update stream_update;
 	} *bundle;
 
-	bundle = kzalloc(sizeof(*bundle), GFP_KERNEL);
+	bundle = kzalloc(sizeof(*bundle), GFP_ATOMIC);
 
 	if (!bundle) {
 		dm_error("Failed to allocate update bundle\n");
diff --git a/drivers/gpu/drm/amd/display/dc/core/dc.c b/drivers/gpu/drm/amd/display/dc/core/dc.c
index 401d1c66a411..a37a32442a5a 100644
--- a/drivers/gpu/drm/amd/display/dc/core/dc.c
+++ b/drivers/gpu/drm/amd/display/dc/core/dc.c
@@ -1416,8 +1416,10 @@ bool dc_post_update_surfaces_to_stream(struct dc *dc)
 
 struct dc_state *dc_create_state(struct dc *dc)
 {
+	/* No you really cant allocate random crap here this late in
+	 * atomic_commit_tail. */
 	struct dc_state *context = kvzalloc(sizeof(struct dc_state),
-					    GFP_KERNEL);
+					    GFP_ATOMIC);
 
 	if (!context)
 		return NULL;
-- 
2.26.2

[RFC 12/17] drm/amdgpu/dc: Stop dma_resv_lock inversion in commit_tail

[Daniel Vetter]

Trying to grab dma_resv_lock while in commit_tail before we've done
all the code that leads to the eventual signalling of the vblank event
(which can be a dma_fence) is deadlock-y. Don't do that.

Here the solution is easy because just grabbing locks to read
something races anyway. We don't need to bother, READ_ONCE is
equivalent. And avoids the locking issue.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
index 9bfaa4cad483..28e1af9f823c 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6699,7 +6699,11 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
 		 * explicitly on fences instead
 		 * and in general should be called for
 		 * blocking commit to as per framework helpers
+		 *
+		 * Yes, this deadlocks, since you're calling dma_resv_lock in a
+		 * path that leads to a dma_fence_signal(). Don't do that.
 		 */
+#if 0
 		r = amdgpu_bo_reserve(abo, true);
 		if (unlikely(r != 0))
 			DRM_ERROR("failed to reserve buffer before flip\n");
@@ -6709,6 +6713,12 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
 		tmz_surface = amdgpu_bo_encrypted(abo);
 
 		amdgpu_bo_unreserve(abo);
+#endif
+		/*
+		 * this races anyway, so READ_ONCE isn't any better or worse
+		 * than the stuff above. Except the stuff above can deadlock.
+		 */
+		tiling_flags = READ_ONCE(abo->tiling_flags);
 
 		fill_dc_plane_info_and_addr(
 			dm->adev, new_plane_state, tiling_flags,
-- 
2.26.2

[RFC 13/17] drm/scheduler: use dma-fence annotations in tdr work

[Daniel Vetter]

In the face of unpriviledged userspace being able to submit bogus gpu
workloads the kernel needs gpu timeout and reset (tdr) to guarantee
that dma_fences actually complete. Annotate this worker to make sure
we don't have any accidental locking inversions or other problems
lurking.

Originally this was part of the overall scheduler annotation patch.
But amdgpu has some glorious inversions here:

- grabs console_lock
- does a full modeset, which grabs all kinds of locks
  (drm_modeset_lock, dma_resv_lock) which can deadlock with
  dma_fence_wait held inside them.
- almost minor at that point, but the modeset code also allocates
  memory

These all look like they'll be very hard to fix properly, the hardware
seems to require a full display reset with any gpu recovery.

Hence split out as a seperate patch.

Since amdgpu isn't the only hardware driver that needs to reset the
display (at least gen2/3 on intel have the same problem) we need a
generic solution for this. There's two tricks we could still from
drm/i915 and lift to dma-fence:

- The big whack, aka force-complete all fences. i915 does this for all
  pending jobs if the reset is somehow stuck. Trouble is we'd need to
  do this for all fences in the entire system, and just the
  book-keeping for that will be fun. Plus lots of drivers use fences
  for all kinds of internal stuff like memory management, so
  unconditionally resetting all of them doesn't work.

  I'm also hoping that with these fence annotations we could enlist
  lockdep in finding the last offenders causing deadlocks, and we
  could remove this get-out-of-jail trick.

- The more feasible approach (across drivers at least as part of the
  dma_fence contract) is what drm/i915 does for gen2/3: When we need
  to reset the display we wake up all dma_fence_wait_interruptible
  calls, or well at least the equivalent of those in i915 internally.

  Relying on ioctl restart we force all other threads to release their
  locks, which means the tdr thread is guaranteed to be able to get
  them. I think we could implement this at the dma_fence level,
  including proper lockdep annotations.

  dma_fence_begin_tdr():
  - must be nested within a dma_fence_begin/end_signalling section
  - will wake up all interruptible (but not the non-interruptible)
    dma_fence_wait() calls and force them to complete with a
    -ERESTARTSYS errno code. All new interrupitble calls to
    dma_fence_wait() will immeidately fail with the same error code.

  dma_fence_end_trdr():
  - this will convert dma_fence_wait() calls back to normal.

  Of course interrupting dma_fence_wait is only ok if the caller
  specified that, which means we need to split the annotations into
  interruptible and non-interruptible version. If we then make sure
  that we only use interruptible dma_fence_wait() calls while holding
  drm_modeset_lock we can grab them in tdr code, and allow display
  resets. Doing the same for dma_resv_lock might be a lot harder, so
  buffer updates must be avoided.

  What's worse, we're not going to be able to make the dma_fence_wait
  calls in mmu-notifiers interruptible, that doesn't work. So
  allocating memory still wont' be allowed, even in tdr sections. Plus
  obviously we can use this trick only in tdr, it is rather intrusive.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/scheduler/sched_main.c | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 06a736e506ad..e34a44376e87 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -279,9 +279,12 @@ static void drm_sched_job_timedout(struct work_struct *work)
 {
 	struct drm_gpu_scheduler *sched;
 	struct drm_sched_job *job;
+	bool fence_cookie;
 
 	sched = container_of(work, struct drm_gpu_scheduler, work_tdr.work);
 
+	fence_cookie = dma_fence_begin_signalling();
+
 	/* Protects against concurrent deletion in drm_sched_get_cleanup_job */
 	spin_lock(&sched->job_list_lock);
 	job = list_first_entry_or_null(&sched->ring_mirror_list,
@@ -313,6 +316,8 @@ static void drm_sched_job_timedout(struct work_struct *work)
 	spin_lock(&sched->job_list_lock);
 	drm_sched_start_timeout(sched);
 	spin_unlock(&sched->job_list_lock);
+
+	dma_fence_end_signalling(fence_cookie);
 }
 
  /**
-- 
2.26.2

[RFC 14/17] drm/amdgpu: use dma-fence annotations for gpu reset code

[Daniel Vetter]

To improve coverage also annotate the gpu reset code itself, since
that's called from other places than drm/scheduler (which is already
annotated). Annotations nests, so this doesn't break anything, and
allows easier testing.

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index b038ddbb2ece..5560d045b2e0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -4140,6 +4140,9 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
 	bool use_baco =
 		(amdgpu_asic_reset_method(adev) == AMD_RESET_METHOD_BACO) ?
 		true : false;
+	bool fence_cookie;
+
+	fence_cookie = dma_fence_begin_signalling();
 
 	/*
 	 * Flush RAM to disk so that after reboot
@@ -4168,6 +4171,7 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
 		DRM_INFO("Bailing on TDR for s_job:%llx, hive: %llx as another already in progress",
 			  job ? job->base.id : -1, hive->hive_id);
 		mutex_unlock(&hive->hive_lock);
+		dma_fence_end_signalling(fence_cookie);
 		return 0;
 	}
 
@@ -4178,8 +4182,10 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
 	 */
 	INIT_LIST_HEAD(&device_list);
 	if (adev->gmc.xgmi.num_physical_nodes > 1) {
-		if (!hive)
+		if (!hive) {
+			dma_fence_end_signalling(fence_cookie);
 			return -ENODEV;
+		}
 		if (!list_is_first(&adev->gmc.xgmi.head, &hive->device_list))
 			list_rotate_to_front(&adev->gmc.xgmi.head, &hive->device_list);
 		device_list_handle = &hive->device_list;
@@ -4194,6 +4200,7 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
 			DRM_INFO("Bailing on TDR for s_job:%llx, as another already in progress",
 				  job ? job->base.id : -1);
 			mutex_unlock(&hive->hive_lock);
+			dma_fence_end_signalling(fence_cookie);
 			return 0;
 		}
 
@@ -4319,6 +4326,7 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
 
 	if (r)
 		dev_info(adev->dev, "GPU reset end with ret = %d\n", r);
+	dma_fence_end_signalling(fence_cookie);
 	return r;
 }
 
-- 
2.26.2

[RFC 15/17] Revert "drm/amdgpu: add fbdev suspend/resume on gpu reset"

[Daniel Vetter]

This is one from the department of "maybe play lottery if you hit
this, karma compensation might work". Or at least lockdep ftw!

This reverts commit 565d1941557756a584ac357d945bc374d5fcd1d0.

It's not quite as low-risk as the commit message claims, because this
grabs console_lock, which might be held when we allocate memory, which
might never happen because the dma_fence_wait() is stuck waiting on
our gpu reset:

[  136.763714] ======================================================
[  136.763714] WARNING: possible circular locking dependency detected
[  136.763715] 5.7.0-rc3+ #346 Tainted: G        W
[  136.763716] ------------------------------------------------------
[  136.763716] kworker/2:3/682 is trying to acquire lock:
[  136.763716] ffffffff8226f140 (console_lock){+.+.}-{0:0}, at: drm_fb_helper_set_suspend_unlocked+0x7b/0xa0 [drm_kms_helper]
[  136.763723]
               but task is already holding lock:
[  136.763724] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
[  136.763726]
               which lock already depends on the new lock.

[  136.763726]
               the existing dependency chain (in reverse order) is:
[  136.763727]
               -> #2 (dma_fence_map){++++}-{0:0}:
[  136.763730]        __dma_fence_might_wait+0x41/0xb0
[  136.763732]        dma_resv_lockdep+0x171/0x202
[  136.763734]        do_one_initcall+0x5d/0x2f0
[  136.763736]        kernel_init_freeable+0x20d/0x26d
[  136.763738]        kernel_init+0xa/0xfb
[  136.763740]        ret_from_fork+0x27/0x50
[  136.763740]
               -> #1 (fs_reclaim){+.+.}-{0:0}:
[  136.763743]        fs_reclaim_acquire.part.0+0x25/0x30
[  136.763745]        kmem_cache_alloc_trace+0x2e/0x6e0
[  136.763747]        device_create_groups_vargs+0x52/0xf0
[  136.763747]        device_create+0x49/0x60
[  136.763749]        fb_console_init+0x25/0x145
[  136.763750]        fbmem_init+0xcc/0xe2
[  136.763750]        do_one_initcall+0x5d/0x2f0
[  136.763751]        kernel_init_freeable+0x20d/0x26d
[  136.763752]        kernel_init+0xa/0xfb
[  136.763753]        ret_from_fork+0x27/0x50
[  136.763753]
               -> #0 (console_lock){+.+.}-{0:0}:
[  136.763755]        __lock_acquire+0x1241/0x23f0
[  136.763756]        lock_acquire+0xad/0x370
[  136.763757]        console_lock+0x47/0x70
[  136.763761]        drm_fb_helper_set_suspend_unlocked+0x7b/0xa0 [drm_kms_helper]
[  136.763809]        amdgpu_device_gpu_recover.cold+0x21e/0xe7b [amdgpu]
[  136.763850]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
[  136.763851]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
[  136.763852]        process_one_work+0x23c/0x580
[  136.763853]        worker_thread+0x50/0x3b0
[  136.763854]        kthread+0x12e/0x150
[  136.763855]        ret_from_fork+0x27/0x50
[  136.763855]
               other info that might help us debug this:

[  136.763856] Chain exists of:
                 console_lock --> fs_reclaim --> dma_fence_map

[  136.763857]  Possible unsafe locking scenario:

[  136.763857]        CPU0                    CPU1
[  136.763857]        ----                    ----
[  136.763857]   lock(dma_fence_map);
[  136.763858]                                lock(fs_reclaim);
[  136.763858]                                lock(dma_fence_map);
[  136.763858]   lock(console_lock);
[  136.763859]
                *** DEADLOCK ***

[  136.763860] 4 locks held by kworker/2:3/682:
[  136.763860]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
[  136.763862]  #1: ffffc90000cafe58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
[  136.763863]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
[  136.763865]  #3: ffff8887ab621748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x5ab/0xe7b [amdgpu]
[  136.763914]
               stack backtrace:
[  136.763915] CPU: 2 PID: 682 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
[  136.763916] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
[  136.763918] Workqueue: events drm_sched_job_timedout [gpu_sched]
[  136.763919] Call Trace:
[  136.763922]  dump_stack+0x8f/0xd0
[  136.763924]  check_noncircular+0x162/0x180
[  136.763926]  __lock_acquire+0x1241/0x23f0
[  136.763927]  lock_acquire+0xad/0x370
[  136.763932]  ? drm_fb_helper_set_suspend_unlocked+0x7b/0xa0 [drm_kms_helper]
[  136.763933]  ? mark_held_locks+0x2d/0x80
[  136.763934]  ? _raw_spin_unlock_irqrestore+0x46/0x60
[  136.763936]  console_lock+0x47/0x70
[  136.763940]  ? drm_fb_helper_set_suspend_unlocked+0x7b/0xa0 [drm_kms_helper]
[  136.763944]  drm_fb_helper_set_suspend_unlocked+0x7b/0xa0 [drm_kms_helper]
[  136.763993]  amdgpu_device_gpu_recover.cold+0x21e/0xe7b [amdgpu]
[  136.764036]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
[  136.764038]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
[  136.764040]  process_one_work+0x23c/0x580
[  136.764041]  worker_thread+0x50/0x3b0
[  136.764042]  ? process_one_work+0x580/0x580
[  136.764044]  kthread+0x12e/0x150
[  136.764045]  ? kthread_create_worker_on_cpu+0x70/0x70
[  136.764046]  ret_from_fork+0x27/0x50

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 4 ----
 1 file changed, 4 deletions(-)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 5560d045b2e0..3584e29323c0 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -4047,8 +4047,6 @@ static int amdgpu_do_asic_reset(struct amdgpu_hive_info *hive,
 				if (r)
 					goto out;
 
-				amdgpu_fbdev_set_suspend(tmp_adev, 0);
-
 				/* must succeed. */
 				amdgpu_ras_resume(tmp_adev);
 
@@ -4217,8 +4215,6 @@ int amdgpu_device_gpu_recover(struct amdgpu_device *adev,
 		 */
 		amdgpu_unregister_gpu_instance(tmp_adev);
 
-		amdgpu_fbdev_set_suspend(tmp_adev, 1);
-
 		/* disable ras on ALL IPs */
 		if (!(in_ras_intr && !use_baco) &&
 		      amdgpu_device_ip_need_full_reset(tmp_adev))
-- 
2.26.2

[RFC 16/17] drm/amdgpu: gpu recovery does full modesets

[Daniel Vetter]

...

I think it's time to stop this little exercise.

The lockdep splat, for the record:

[  132.583381] ======================================================
[  132.584091] WARNING: possible circular locking dependency detected
[  132.584775] 5.7.0-rc3+ #346 Tainted: G        W
[  132.585461] ------------------------------------------------------
[  132.586184] kworker/2:3/865 is trying to acquire lock:
[  132.586857] ffffc90000677c70 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
[  132.587569]
               but task is already holding lock:
[  132.589044] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
[  132.589803]
               which lock already depends on the new lock.

[  132.592009]
               the existing dependency chain (in reverse order) is:
[  132.593507]
               -> #2 (dma_fence_map){++++}-{0:0}:
[  132.595019]        dma_fence_begin_signalling+0x50/0x60
[  132.595767]        drm_atomic_helper_commit+0xa1/0x180 [drm_kms_helper]
[  132.596567]        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
[  132.597420]        drm_client_modeset_commit_locked+0x55/0x190 [drm]
[  132.598178]        drm_client_modeset_commit+0x24/0x40 [drm]
[  132.598948]        drm_fb_helper_restore_fbdev_mode_unlocked+0x4b/0xa0 [drm_kms_helper]
[  132.599738]        drm_fb_helper_set_par+0x30/0x40 [drm_kms_helper]
[  132.600539]        fbcon_init+0x2e8/0x660
[  132.601344]        visual_init+0xce/0x130
[  132.602156]        do_bind_con_driver+0x1bc/0x2b0
[  132.602970]        do_take_over_console+0x115/0x180
[  132.603763]        do_fbcon_takeover+0x58/0xb0
[  132.604564]        register_framebuffer+0x1ee/0x300
[  132.605369]        __drm_fb_helper_initial_config_and_unlock+0x36e/0x520 [drm_kms_helper]
[  132.606187]        amdgpu_fbdev_init+0xb3/0xf0 [amdgpu]
[  132.607032]        amdgpu_device_init.cold+0xe90/0x1677 [amdgpu]
[  132.607862]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
[  132.608697]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
[  132.609511]        local_pci_probe+0x42/0x80
[  132.610324]        pci_device_probe+0x104/0x1a0
[  132.611130]        really_probe+0x147/0x3c0
[  132.611939]        driver_probe_device+0xb6/0x100
[  132.612766]        device_driver_attach+0x53/0x60
[  132.613593]        __driver_attach+0x8c/0x150
[  132.614419]        bus_for_each_dev+0x7b/0xc0
[  132.615249]        bus_add_driver+0x14c/0x1f0
[  132.616071]        driver_register+0x6c/0xc0
[  132.616902]        do_one_initcall+0x5d/0x2f0
[  132.617731]        do_init_module+0x5c/0x230
[  132.618560]        load_module+0x2981/0x2bc0
[  132.619391]        __do_sys_finit_module+0xaa/0x110
[  132.620228]        do_syscall_64+0x5a/0x250
[  132.621064]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
[  132.621903]
               -> #1 (crtc_ww_class_mutex){+.+.}-{3:3}:
[  132.623587]        __ww_mutex_lock.constprop.0+0xcc/0x10c0
[  132.624448]        ww_mutex_lock+0x43/0xb0
[  132.625315]        drm_modeset_lock+0x44/0x120 [drm]
[  132.626184]        drmm_mode_config_init+0x2db/0x8b0 [drm]
[  132.627098]        amdgpu_device_init.cold+0xbd1/0x1677 [amdgpu]
[  132.628007]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
[  132.628920]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
[  132.629804]        local_pci_probe+0x42/0x80
[  132.630690]        pci_device_probe+0x104/0x1a0
[  132.631583]        really_probe+0x147/0x3c0
[  132.632479]        driver_probe_device+0xb6/0x100
[  132.633379]        device_driver_attach+0x53/0x60
[  132.634275]        __driver_attach+0x8c/0x150
[  132.635170]        bus_for_each_dev+0x7b/0xc0
[  132.636069]        bus_add_driver+0x14c/0x1f0
[  132.636974]        driver_register+0x6c/0xc0
[  132.637870]        do_one_initcall+0x5d/0x2f0
[  132.638765]        do_init_module+0x5c/0x230
[  132.639654]        load_module+0x2981/0x2bc0
[  132.640522]        __do_sys_finit_module+0xaa/0x110
[  132.641372]        do_syscall_64+0x5a/0x250
[  132.642203]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
[  132.643022]
               -> #0 (crtc_ww_class_acquire){+.+.}-{0:0}:
[  132.644643]        __lock_acquire+0x1241/0x23f0
[  132.645469]        lock_acquire+0xad/0x370
[  132.646274]        drm_modeset_acquire_init+0xd2/0x100 [drm]
[  132.647071]        drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
[  132.647902]        dm_suspend+0x1c/0x60 [amdgpu]
[  132.648698]        amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
[  132.649498]        amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
[  132.650300]        amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
[  132.651084]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
[  132.651825]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
[  132.652594]        process_one_work+0x23c/0x580
[  132.653402]        worker_thread+0x50/0x3b0
[  132.654139]        kthread+0x12e/0x150
[  132.654868]        ret_from_fork+0x27/0x50
[  132.655598]
               other info that might help us debug this:

[  132.657739] Chain exists of:
                 crtc_ww_class_acquire --> crtc_ww_class_mutex --> dma_fence_map

[  132.659877]  Possible unsafe locking scenario:

[  132.661416]        CPU0                    CPU1
[  132.662126]        ----                    ----
[  132.662847]   lock(dma_fence_map);
[  132.663574]                                lock(crtc_ww_class_mutex);
[  132.664319]                                lock(dma_fence_map);
[  132.665063]   lock(crtc_ww_class_acquire);
[  132.665799]
                *** DEADLOCK ***

[  132.667965] 4 locks held by kworker/2:3/865:
[  132.668701]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
[  132.669462]  #1: ffffc90000677e58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
[  132.670242]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
[  132.671039]  #3: ffff8887b84a1748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x59e/0xe64 [amdgpu]
[  132.671902]
               stack backtrace:
[  132.673515] CPU: 2 PID: 865 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
[  132.674347] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
[  132.675194] Workqueue: events drm_sched_job_timedout [gpu_sched]
[  132.676046] Call Trace:
[  132.676897]  dump_stack+0x8f/0xd0
[  132.677748]  check_noncircular+0x162/0x180
[  132.678604]  ? stack_trace_save+0x4b/0x70
[  132.679459]  __lock_acquire+0x1241/0x23f0
[  132.680311]  lock_acquire+0xad/0x370
[  132.681163]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
[  132.682021]  ? cpumask_next+0x16/0x20
[  132.682880]  ? module_assert_mutex_or_preempt+0x14/0x40
[  132.683737]  ? __module_address+0x28/0xf0
[  132.684601]  drm_modeset_acquire_init+0xd2/0x100 [drm]
[  132.685466]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
[  132.686335]  drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
[  132.687255]  dm_suspend+0x1c/0x60 [amdgpu]
[  132.688152]  amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
[  132.689057]  ? amdgpu_fence_process+0x4c/0x150 [amdgpu]
[  132.689963]  amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
[  132.690893]  amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
[  132.691818]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
[  132.692707]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
[  132.693597]  process_one_work+0x23c/0x580
[  132.694487]  worker_thread+0x50/0x3b0
[  132.695373]  ? process_one_work+0x580/0x580
[  132.696264]  kthread+0x12e/0x150
[  132.697154]  ? kthread_create_worker_on_cpu+0x70/0x70
[  132.698057]  ret_from_fork+0x27/0x50

Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
index 3584e29323c0..b3b84a0d3baf 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
@@ -2415,6 +2415,14 @@ static int amdgpu_device_ip_suspend_phase1(struct amdgpu_device *adev)
 		/* displays are handled separately */
 		if (adev->ip_blocks[i].version->type == AMD_IP_BLOCK_TYPE_DCE) {
 			/* XXX handle errors */
+
+			/*
+			 * This is dm_suspend, which calls modeset locks, and
+			 * that a pretty good inversion against dma_fence_signal
+			 * which gpu recovery is supposed to guarantee.
+			 *
+			 * Dont ask me how to fix this.
+			 */
 			r = adev->ip_blocks[i].version->funcs->suspend(adev);
 			/* XXX handle errors */
 			if (r) {
-- 
2.26.2

[RFC 17/17] drm/i915: Annotate dma_fence_work

[Daniel Vetter]

i915 does tons of allocations from this worker, which lockdep catches.

Also generic infrastructure like this with big potential for how
dma_fence or other cross driver contracts work, really should be
reviewed on dri-devel. Implementing custom wheels for everything
within the driver is a classic case of "platform problem" [1]. Which in
upstream we really shouldn't have.

Since there's no quick way to solve these splats (dma_fence_work is
used a bunch in basic buffer management and command submission) like
for amdgpu, I'm giving up at this point here. Annotating i915
scheduler and gpu reset could would be interesting, but since lockdep
is one-shot we can't see what surprises would lurk there.

1: https://lwn.net/Articles/443531/
Cc: linux-media@vger.kernel.org
Cc: linaro-mm-sig@lists.linaro.org
Cc: linux-rdma@vger.kernel.org
Cc: amd-gfx@lists.freedesktop.org
Cc: intel-gfx@lists.freedesktop.org
Cc: Chris Wilson <chris@chris-wilson.co.uk>
Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Cc: Christian König <christian.koenig@amd.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
---
 drivers/gpu/drm/i915/i915_sw_fence_work.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/i915/i915_sw_fence_work.c b/drivers/gpu/drm/i915/i915_sw_fence_work.c
index a3a81bb8f2c3..5b74acadaef5 100644
--- a/drivers/gpu/drm/i915/i915_sw_fence_work.c
+++ b/drivers/gpu/drm/i915/i915_sw_fence_work.c
@@ -17,12 +17,15 @@ static void fence_work(struct work_struct *work)
 {
 	struct dma_fence_work *f = container_of(work, typeof(*f), work);
 	int err;
+	bool fence_cookie;
 
+	fence_cookie = dma_fence_begin_signalling();
 	err = f->ops->work(f);
 	if (err)
 		dma_fence_set_error(&f->dma, err);
 
 	fence_complete(f);
+	dma_fence_end_signalling(fence_cookie);
 	dma_fence_put(&f->dma);
 }
 
-- 
2.26.2

Re: [RFC 01/17] dma-fence: add might_sleep annotation to _wait()

[Christian König]

Am 12.05.20 um 10:59 schrieb Daniel Vetter:
> But only for non-zero timeout, to avoid false positives.
>
> One question here is whether the might_sleep should be unconditional,
> or only for real timeouts. I'm not sure, so went with the more
> defensive option. But in the interest of locking down the cross-driver
> dma_fence rules we might want to be more aggressive.
>
> Cc: linux-media@vger.kernel.org
> Cc: linaro-mm-sig@lists.linaro.org
> Cc: linux-rdma@vger.kernel.org
> Cc: amd-gfx@lists.freedesktop.org
> Cc: intel-gfx@lists.freedesktop.org
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Christian König <christian.koenig@amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
>   drivers/dma-buf/dma-fence.c | 3 +++
>   1 file changed, 3 insertions(+)
>
> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> index 052a41e2451c..6802125349fb 100644
> --- a/drivers/dma-buf/dma-fence.c
> +++ b/drivers/dma-buf/dma-fence.c
> @@ -208,6 +208,9 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
>   	if (WARN_ON(timeout < 0))
>   		return -EINVAL;
>   
> +	if (timeout > 0)
> +		might_sleep();
> +

I would rather like to see might_sleep() called here all the time even 
with timeout==0.

IIRC I removed the code in TTM abusing this in atomic context quite a 
while ago, but could be that some leaked in again or it is called in 
atomic context elsewhere as well.

Christian.

>   	trace_dma_fence_wait_start(fence);
>   	if (fence->ops->wait)
>   		ret = fence->ops->wait(fence, intr, timeout);

Re: [RFC 02/17] dma-fence: basic lockdep annotations

[Daniel Vetter]

On Tue, May 12, 2020 at 10:04:22AM +0100, Chris Wilson wrote:
> Quoting Daniel Vetter (2020-05-12 09:59:29)
> > Design is similar to the lockdep annotations for workers, but with
> > some twists:
> > 
> > - We use a read-lock for the execution/worker/completion side, so that
> >   this explicit annotation can be more liberally sprinkled around.
> >   With read locks lockdep isn't going to complain if the read-side
> >   isn't nested the same way under all circumstances, so ABBA deadlocks
> >   are ok. Which they are, since this is an annotation only.
> > 
> > - We're using non-recursive lockdep read lock mode, since in recursive
> >   read lock mode lockdep does not catch read side hazards. And we
> >   _very_ much want read side hazards to be caught. For full details of
> >   this limitation see
> > 
> >   commit e91498589746065e3ae95d9a00b068e525eec34f
> >   Author: Peter Zijlstra <peterz@infradead.org>
> >   Date:   Wed Aug 23 13:13:11 2017 +0200
> > 
> >       locking/lockdep/selftests: Add mixed read-write ABBA tests
> > 
> > - To allow nesting of the read-side explicit annotations we explicitly
> >   keep track of the nesting. lock_is_held() allows us to do that.
> > 
> > - The wait-side annotation is a write lock, and entirely done within
> >   dma_fence_wait() for everyone by default.
> > 
> > - To be able to freely annotate helper functions I want to make it ok
> >   to call dma_fence_begin/end_signalling from soft/hardirq context.
> >   First attempt was using the hardirq locking context for the write
> >   side in lockdep, but this forces all normal spinlocks nested within
> >   dma_fence_begin/end_signalling to be spinlocks. That bollocks.
> > 
> >   The approach now is to simple check in_atomic(), and for these cases
> >   entirely rely on the might_sleep() check in dma_fence_wait(). That
> >   will catch any wrong nesting against spinlocks from soft/hardirq
> >   contexts.
> > 
> > The idea here is that every code path that's critical for eventually
> > signalling a dma_fence should be annotated with
> > dma_fence_begin/end_signalling. The annotation ideally starts right
> > after a dma_fence is published (added to a dma_resv, exposed as a
> > sync_file fd, attached to a drm_syncobj fd, or anything else that
> > makes the dma_fence visible to other kernel threads), up to and
> > including the dma_fence_wait(). Examples are irq handlers, the
> > scheduler rt threads, the tail of execbuf (after the corresponding
> > fences are visible), any workers that end up signalling dma_fences and
> > really anything else. Not annotated should be code paths that only
> > complete fences opportunistically as the gpu progresses, like e.g.
> > shrinker/eviction code.
> > 
> > The main class of deadlocks this is supposed to catch are:
> > 
> > Thread A:
> > 
> >         mutex_lock(A);
> >         mutex_unlock(A);
> > 
> >         dma_fence_signal();
> > 
> > Thread B:
> > 
> >         mutex_lock(A);
> >         dma_fence_wait();
> >         mutex_unlock(A);
> > 
> > Thread B is blocked on A signalling the fence, but A never gets around
> > to that because it cannot acquire the lock A.
> > 
> > Note that dma_fence_wait() is allowed to be nested within
> > dma_fence_begin/end_signalling sections. To allow this to happen the
> > read lock needs to be upgraded to a write lock, which means that any
> > other lock is acquired between the dma_fence_begin_signalling() call and
> > the call to dma_fence_wait(), and still held, this will result in an
> > immediate lockdep complaint. The only other option would be to not
> > annotate such calls, defeating the point. Therefore these annotations
> > cannot be sprinkled over the code entirely mindless to avoid false
> > positives.
> > 
> > v2: handle soft/hardirq ctx better against write side and dont forget
> > EXPORT_SYMBOL, drivers can't use this otherwise.
> > 
> > Cc: linux-media@vger.kernel.org
> > Cc: linaro-mm-sig@lists.linaro.org
> > Cc: linux-rdma@vger.kernel.org
> > Cc: amd-gfx@lists.freedesktop.org
> > Cc: intel-gfx@lists.freedesktop.org
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Christian König <christian.koenig@amd.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > ---
> >  drivers/dma-buf/dma-fence.c | 53 +++++++++++++++++++++++++++++++++++++
> >  include/linux/dma-fence.h   | 12 +++++++++
> >  2 files changed, 65 insertions(+)
> > 
> > diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> > index 6802125349fb..d5c0fd2efc70 100644
> > --- a/drivers/dma-buf/dma-fence.c
> > +++ b/drivers/dma-buf/dma-fence.c
> > @@ -110,6 +110,52 @@ u64 dma_fence_context_alloc(unsigned num)
> >  }
> >  EXPORT_SYMBOL(dma_fence_context_alloc);
> >  
> > +#ifdef CONFIG_LOCKDEP
> > +struct lockdep_map     dma_fence_lockdep_map = {
> > +       .name = "dma_fence_map"
> > +};
> 
> Not another false global sharing lockmap.

It's a global contract, it needs a global lockdep map. And yes a big
reason for the motivation here is that i915-gem has a tremendous urge to
just redefine all these global locks to fit to some local interpretation
of what's going on.

That doesn't make the resulting real&existing deadlocks go away.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [RFC 02/17] dma-fence: basic lockdep annotations

[Jason Gunthorpe]

On Tue, May 12, 2020 at 10:59:29AM +0200, Daniel Vetter wrote:
> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> index 6802125349fb..d5c0fd2efc70 100644
> +++ b/drivers/dma-buf/dma-fence.c
> @@ -110,6 +110,52 @@ u64 dma_fence_context_alloc(unsigned num)
>  }
>  EXPORT_SYMBOL(dma_fence_context_alloc);
>  
> +#ifdef CONFIG_LOCKDEP
> +struct lockdep_map	dma_fence_lockdep_map = {
> +	.name = "dma_fence_map"
> +};
> +
> +bool dma_fence_begin_signalling(void)
> +{

Why is this global? I would have expected it to be connected to a
single fence?

It would also be alot nicer if this was some general lockdep feature,
not tied to dmabuf. This exact problem also strikes anyone using
completions, for instance, and the same solution should be
applicable??

Jason

Re: [RFC 16/17] drm/amdgpu: gpu recovery does full modesets

[Alex Deucher]

On Tue, May 12, 2020 at 5:00 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>
> ...
>
> I think it's time to stop this little exercise.
>
> The lockdep splat, for the record:
>
> [  132.583381] ======================================================
> [  132.584091] WARNING: possible circular locking dependency detected
> [  132.584775] 5.7.0-rc3+ #346 Tainted: G        W
> [  132.585461] ------------------------------------------------------
> [  132.586184] kworker/2:3/865 is trying to acquire lock:
> [  132.586857] ffffc90000677c70 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> [  132.587569]
>                but task is already holding lock:
> [  132.589044] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> [  132.589803]
>                which lock already depends on the new lock.
>
> [  132.592009]
>                the existing dependency chain (in reverse order) is:
> [  132.593507]
>                -> #2 (dma_fence_map){++++}-{0:0}:
> [  132.595019]        dma_fence_begin_signalling+0x50/0x60
> [  132.595767]        drm_atomic_helper_commit+0xa1/0x180 [drm_kms_helper]
> [  132.596567]        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
> [  132.597420]        drm_client_modeset_commit_locked+0x55/0x190 [drm]
> [  132.598178]        drm_client_modeset_commit+0x24/0x40 [drm]
> [  132.598948]        drm_fb_helper_restore_fbdev_mode_unlocked+0x4b/0xa0 [drm_kms_helper]
> [  132.599738]        drm_fb_helper_set_par+0x30/0x40 [drm_kms_helper]
> [  132.600539]        fbcon_init+0x2e8/0x660
> [  132.601344]        visual_init+0xce/0x130
> [  132.602156]        do_bind_con_driver+0x1bc/0x2b0
> [  132.602970]        do_take_over_console+0x115/0x180
> [  132.603763]        do_fbcon_takeover+0x58/0xb0
> [  132.604564]        register_framebuffer+0x1ee/0x300
> [  132.605369]        __drm_fb_helper_initial_config_and_unlock+0x36e/0x520 [drm_kms_helper]
> [  132.606187]        amdgpu_fbdev_init+0xb3/0xf0 [amdgpu]
> [  132.607032]        amdgpu_device_init.cold+0xe90/0x1677 [amdgpu]
> [  132.607862]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> [  132.608697]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> [  132.609511]        local_pci_probe+0x42/0x80
> [  132.610324]        pci_device_probe+0x104/0x1a0
> [  132.611130]        really_probe+0x147/0x3c0
> [  132.611939]        driver_probe_device+0xb6/0x100
> [  132.612766]        device_driver_attach+0x53/0x60
> [  132.613593]        __driver_attach+0x8c/0x150
> [  132.614419]        bus_for_each_dev+0x7b/0xc0
> [  132.615249]        bus_add_driver+0x14c/0x1f0
> [  132.616071]        driver_register+0x6c/0xc0
> [  132.616902]        do_one_initcall+0x5d/0x2f0
> [  132.617731]        do_init_module+0x5c/0x230
> [  132.618560]        load_module+0x2981/0x2bc0
> [  132.619391]        __do_sys_finit_module+0xaa/0x110
> [  132.620228]        do_syscall_64+0x5a/0x250
> [  132.621064]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> [  132.621903]
>                -> #1 (crtc_ww_class_mutex){+.+.}-{3:3}:
> [  132.623587]        __ww_mutex_lock.constprop.0+0xcc/0x10c0
> [  132.624448]        ww_mutex_lock+0x43/0xb0
> [  132.625315]        drm_modeset_lock+0x44/0x120 [drm]
> [  132.626184]        drmm_mode_config_init+0x2db/0x8b0 [drm]
> [  132.627098]        amdgpu_device_init.cold+0xbd1/0x1677 [amdgpu]
> [  132.628007]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> [  132.628920]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> [  132.629804]        local_pci_probe+0x42/0x80
> [  132.630690]        pci_device_probe+0x104/0x1a0
> [  132.631583]        really_probe+0x147/0x3c0
> [  132.632479]        driver_probe_device+0xb6/0x100
> [  132.633379]        device_driver_attach+0x53/0x60
> [  132.634275]        __driver_attach+0x8c/0x150
> [  132.635170]        bus_for_each_dev+0x7b/0xc0
> [  132.636069]        bus_add_driver+0x14c/0x1f0
> [  132.636974]        driver_register+0x6c/0xc0
> [  132.637870]        do_one_initcall+0x5d/0x2f0
> [  132.638765]        do_init_module+0x5c/0x230
> [  132.639654]        load_module+0x2981/0x2bc0
> [  132.640522]        __do_sys_finit_module+0xaa/0x110
> [  132.641372]        do_syscall_64+0x5a/0x250
> [  132.642203]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> [  132.643022]
>                -> #0 (crtc_ww_class_acquire){+.+.}-{0:0}:
> [  132.644643]        __lock_acquire+0x1241/0x23f0
> [  132.645469]        lock_acquire+0xad/0x370
> [  132.646274]        drm_modeset_acquire_init+0xd2/0x100 [drm]
> [  132.647071]        drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> [  132.647902]        dm_suspend+0x1c/0x60 [amdgpu]
> [  132.648698]        amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> [  132.649498]        amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> [  132.650300]        amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> [  132.651084]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> [  132.651825]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> [  132.652594]        process_one_work+0x23c/0x580
> [  132.653402]        worker_thread+0x50/0x3b0
> [  132.654139]        kthread+0x12e/0x150
> [  132.654868]        ret_from_fork+0x27/0x50
> [  132.655598]
>                other info that might help us debug this:
>
> [  132.657739] Chain exists of:
>                  crtc_ww_class_acquire --> crtc_ww_class_mutex --> dma_fence_map
>
> [  132.659877]  Possible unsafe locking scenario:
>
> [  132.661416]        CPU0                    CPU1
> [  132.662126]        ----                    ----
> [  132.662847]   lock(dma_fence_map);
> [  132.663574]                                lock(crtc_ww_class_mutex);
> [  132.664319]                                lock(dma_fence_map);
> [  132.665063]   lock(crtc_ww_class_acquire);
> [  132.665799]
>                 *** DEADLOCK ***
>
> [  132.667965] 4 locks held by kworker/2:3/865:
> [  132.668701]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> [  132.669462]  #1: ffffc90000677e58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> [  132.670242]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> [  132.671039]  #3: ffff8887b84a1748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x59e/0xe64 [amdgpu]
> [  132.671902]
>                stack backtrace:
> [  132.673515] CPU: 2 PID: 865 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
> [  132.674347] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
> [  132.675194] Workqueue: events drm_sched_job_timedout [gpu_sched]
> [  132.676046] Call Trace:
> [  132.676897]  dump_stack+0x8f/0xd0
> [  132.677748]  check_noncircular+0x162/0x180
> [  132.678604]  ? stack_trace_save+0x4b/0x70
> [  132.679459]  __lock_acquire+0x1241/0x23f0
> [  132.680311]  lock_acquire+0xad/0x370
> [  132.681163]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> [  132.682021]  ? cpumask_next+0x16/0x20
> [  132.682880]  ? module_assert_mutex_or_preempt+0x14/0x40
> [  132.683737]  ? __module_address+0x28/0xf0
> [  132.684601]  drm_modeset_acquire_init+0xd2/0x100 [drm]
> [  132.685466]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> [  132.686335]  drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> [  132.687255]  dm_suspend+0x1c/0x60 [amdgpu]
> [  132.688152]  amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> [  132.689057]  ? amdgpu_fence_process+0x4c/0x150 [amdgpu]
> [  132.689963]  amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> [  132.690893]  amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> [  132.691818]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> [  132.692707]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> [  132.693597]  process_one_work+0x23c/0x580
> [  132.694487]  worker_thread+0x50/0x3b0
> [  132.695373]  ? process_one_work+0x580/0x580
> [  132.696264]  kthread+0x12e/0x150
> [  132.697154]  ? kthread_create_worker_on_cpu+0x70/0x70
> [  132.698057]  ret_from_fork+0x27/0x50
>
> Cc: linux-media@vger.kernel.org
> Cc: linaro-mm-sig@lists.linaro.org
> Cc: linux-rdma@vger.kernel.org
> Cc: amd-gfx@lists.freedesktop.org
> Cc: intel-gfx@lists.freedesktop.org
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Christian König <christian.koenig@amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> index 3584e29323c0..b3b84a0d3baf 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> @@ -2415,6 +2415,14 @@ static int amdgpu_device_ip_suspend_phase1(struct amdgpu_device *adev)
>                 /* displays are handled separately */
>                 if (adev->ip_blocks[i].version->type == AMD_IP_BLOCK_TYPE_DCE) {
>                         /* XXX handle errors */
> +
> +                       /*
> +                        * This is dm_suspend, which calls modeset locks, and
> +                        * that a pretty good inversion against dma_fence_signal
> +                        * which gpu recovery is supposed to guarantee.
> +                        *
> +                        * Dont ask me how to fix this.
> +                        */

We actually have a fix for this.  Will be out shortly.

Alex

>                         r = adev->ip_blocks[i].version->funcs->suspend(adev);
>                         /* XXX handle errors */
>                         if (r) {
> --
> 2.26.2
>
> _______________________________________________
> amd-gfx mailing list
> amd-gfx@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/amd-gfx

Re: [RFC 02/17] dma-fence: basic lockdep annotations

[Daniel Vetter]

On Tue, May 12, 2020 at 09:09:52AM -0300, Jason Gunthorpe wrote:
> On Tue, May 12, 2020 at 10:59:29AM +0200, Daniel Vetter wrote:
> > diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> > index 6802125349fb..d5c0fd2efc70 100644
> > +++ b/drivers/dma-buf/dma-fence.c
> > @@ -110,6 +110,52 @@ u64 dma_fence_context_alloc(unsigned num)
> >  }
> >  EXPORT_SYMBOL(dma_fence_context_alloc);
> >  
> > +#ifdef CONFIG_LOCKDEP
> > +struct lockdep_map	dma_fence_lockdep_map = {
> > +	.name = "dma_fence_map"
> > +};
> > +
> > +bool dma_fence_begin_signalling(void)
> > +{
> 
> Why is this global? I would have expected it to be connected to a
> single fence?

It's the same rules for all fences, since they can be shared across
drivers in various ways. Lockdep usually achieves that with a static
variable hidden in the macro, but that doesn't work if you have lots of
different ways from different drivers to create a dma_fence. Hence the
unique global one that we explicitly allocate.

We have similar stuff for the global dma_resv_lock ww_mutex class, just
there it's a bit more standardized and hidden behind a neat macro. But
really lockdep needs global lockdep_maps or it doesn't work.

> It would also be alot nicer if this was some general lockdep feature,
> not tied to dmabuf. This exact problem also strikes anyone using
> completions, for instance, and the same solution should be
> applicable??

There was:

https://lwn.net/Articles/709849/

It even got merged, and seems to have worked. Unfortunately (and I'm not
entirely clear on the reasons) it was thrown out again, so we can't use
it. That means wait_event/wake_up dependencies need to be manually
annotated, like e.g. flush_work() already is. flush_work is more or less
where I've stolen this idea from, with some adjustements and tricks on top
to make it work for dma_fence users.

Cheers, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [RFC 16/17] drm/amdgpu: gpu recovery does full modesets

[Daniel Vetter]

On Tue, May 12, 2020 at 08:54:45AM -0400, Alex Deucher wrote:
> On Tue, May 12, 2020 at 5:00 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >
> > ...
> >
> > I think it's time to stop this little exercise.
> >
> > The lockdep splat, for the record:
> >
> > [  132.583381] ======================================================
> > [  132.584091] WARNING: possible circular locking dependency detected
> > [  132.584775] 5.7.0-rc3+ #346 Tainted: G        W
> > [  132.585461] ------------------------------------------------------
> > [  132.586184] kworker/2:3/865 is trying to acquire lock:
> > [  132.586857] ffffc90000677c70 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > [  132.587569]
> >                but task is already holding lock:
> > [  132.589044] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > [  132.589803]
> >                which lock already depends on the new lock.
> >
> > [  132.592009]
> >                the existing dependency chain (in reverse order) is:
> > [  132.593507]
> >                -> #2 (dma_fence_map){++++}-{0:0}:
> > [  132.595019]        dma_fence_begin_signalling+0x50/0x60
> > [  132.595767]        drm_atomic_helper_commit+0xa1/0x180 [drm_kms_helper]
> > [  132.596567]        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
> > [  132.597420]        drm_client_modeset_commit_locked+0x55/0x190 [drm]
> > [  132.598178]        drm_client_modeset_commit+0x24/0x40 [drm]
> > [  132.598948]        drm_fb_helper_restore_fbdev_mode_unlocked+0x4b/0xa0 [drm_kms_helper]
> > [  132.599738]        drm_fb_helper_set_par+0x30/0x40 [drm_kms_helper]
> > [  132.600539]        fbcon_init+0x2e8/0x660
> > [  132.601344]        visual_init+0xce/0x130
> > [  132.602156]        do_bind_con_driver+0x1bc/0x2b0
> > [  132.602970]        do_take_over_console+0x115/0x180
> > [  132.603763]        do_fbcon_takeover+0x58/0xb0
> > [  132.604564]        register_framebuffer+0x1ee/0x300
> > [  132.605369]        __drm_fb_helper_initial_config_and_unlock+0x36e/0x520 [drm_kms_helper]
> > [  132.606187]        amdgpu_fbdev_init+0xb3/0xf0 [amdgpu]
> > [  132.607032]        amdgpu_device_init.cold+0xe90/0x1677 [amdgpu]
> > [  132.607862]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > [  132.608697]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > [  132.609511]        local_pci_probe+0x42/0x80
> > [  132.610324]        pci_device_probe+0x104/0x1a0
> > [  132.611130]        really_probe+0x147/0x3c0
> > [  132.611939]        driver_probe_device+0xb6/0x100
> > [  132.612766]        device_driver_attach+0x53/0x60
> > [  132.613593]        __driver_attach+0x8c/0x150
> > [  132.614419]        bus_for_each_dev+0x7b/0xc0
> > [  132.615249]        bus_add_driver+0x14c/0x1f0
> > [  132.616071]        driver_register+0x6c/0xc0
> > [  132.616902]        do_one_initcall+0x5d/0x2f0
> > [  132.617731]        do_init_module+0x5c/0x230
> > [  132.618560]        load_module+0x2981/0x2bc0
> > [  132.619391]        __do_sys_finit_module+0xaa/0x110
> > [  132.620228]        do_syscall_64+0x5a/0x250
> > [  132.621064]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > [  132.621903]
> >                -> #1 (crtc_ww_class_mutex){+.+.}-{3:3}:
> > [  132.623587]        __ww_mutex_lock.constprop.0+0xcc/0x10c0
> > [  132.624448]        ww_mutex_lock+0x43/0xb0
> > [  132.625315]        drm_modeset_lock+0x44/0x120 [drm]
> > [  132.626184]        drmm_mode_config_init+0x2db/0x8b0 [drm]
> > [  132.627098]        amdgpu_device_init.cold+0xbd1/0x1677 [amdgpu]
> > [  132.628007]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > [  132.628920]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > [  132.629804]        local_pci_probe+0x42/0x80
> > [  132.630690]        pci_device_probe+0x104/0x1a0
> > [  132.631583]        really_probe+0x147/0x3c0
> > [  132.632479]        driver_probe_device+0xb6/0x100
> > [  132.633379]        device_driver_attach+0x53/0x60
> > [  132.634275]        __driver_attach+0x8c/0x150
> > [  132.635170]        bus_for_each_dev+0x7b/0xc0
> > [  132.636069]        bus_add_driver+0x14c/0x1f0
> > [  132.636974]        driver_register+0x6c/0xc0
> > [  132.637870]        do_one_initcall+0x5d/0x2f0
> > [  132.638765]        do_init_module+0x5c/0x230
> > [  132.639654]        load_module+0x2981/0x2bc0
> > [  132.640522]        __do_sys_finit_module+0xaa/0x110
> > [  132.641372]        do_syscall_64+0x5a/0x250
> > [  132.642203]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > [  132.643022]
> >                -> #0 (crtc_ww_class_acquire){+.+.}-{0:0}:
> > [  132.644643]        __lock_acquire+0x1241/0x23f0
> > [  132.645469]        lock_acquire+0xad/0x370
> > [  132.646274]        drm_modeset_acquire_init+0xd2/0x100 [drm]
> > [  132.647071]        drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > [  132.647902]        dm_suspend+0x1c/0x60 [amdgpu]
> > [  132.648698]        amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > [  132.649498]        amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > [  132.650300]        amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > [  132.651084]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > [  132.651825]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > [  132.652594]        process_one_work+0x23c/0x580
> > [  132.653402]        worker_thread+0x50/0x3b0
> > [  132.654139]        kthread+0x12e/0x150
> > [  132.654868]        ret_from_fork+0x27/0x50
> > [  132.655598]
> >                other info that might help us debug this:
> >
> > [  132.657739] Chain exists of:
> >                  crtc_ww_class_acquire --> crtc_ww_class_mutex --> dma_fence_map
> >
> > [  132.659877]  Possible unsafe locking scenario:
> >
> > [  132.661416]        CPU0                    CPU1
> > [  132.662126]        ----                    ----
> > [  132.662847]   lock(dma_fence_map);
> > [  132.663574]                                lock(crtc_ww_class_mutex);
> > [  132.664319]                                lock(dma_fence_map);
> > [  132.665063]   lock(crtc_ww_class_acquire);
> > [  132.665799]
> >                 *** DEADLOCK ***
> >
> > [  132.667965] 4 locks held by kworker/2:3/865:
> > [  132.668701]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > [  132.669462]  #1: ffffc90000677e58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > [  132.670242]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > [  132.671039]  #3: ffff8887b84a1748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x59e/0xe64 [amdgpu]
> > [  132.671902]
> >                stack backtrace:
> > [  132.673515] CPU: 2 PID: 865 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
> > [  132.674347] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
> > [  132.675194] Workqueue: events drm_sched_job_timedout [gpu_sched]
> > [  132.676046] Call Trace:
> > [  132.676897]  dump_stack+0x8f/0xd0
> > [  132.677748]  check_noncircular+0x162/0x180
> > [  132.678604]  ? stack_trace_save+0x4b/0x70
> > [  132.679459]  __lock_acquire+0x1241/0x23f0
> > [  132.680311]  lock_acquire+0xad/0x370
> > [  132.681163]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > [  132.682021]  ? cpumask_next+0x16/0x20
> > [  132.682880]  ? module_assert_mutex_or_preempt+0x14/0x40
> > [  132.683737]  ? __module_address+0x28/0xf0
> > [  132.684601]  drm_modeset_acquire_init+0xd2/0x100 [drm]
> > [  132.685466]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > [  132.686335]  drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > [  132.687255]  dm_suspend+0x1c/0x60 [amdgpu]
> > [  132.688152]  amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > [  132.689057]  ? amdgpu_fence_process+0x4c/0x150 [amdgpu]
> > [  132.689963]  amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > [  132.690893]  amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > [  132.691818]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > [  132.692707]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > [  132.693597]  process_one_work+0x23c/0x580
> > [  132.694487]  worker_thread+0x50/0x3b0
> > [  132.695373]  ? process_one_work+0x580/0x580
> > [  132.696264]  kthread+0x12e/0x150
> > [  132.697154]  ? kthread_create_worker_on_cpu+0x70/0x70
> > [  132.698057]  ret_from_fork+0x27/0x50
> >
> > Cc: linux-media@vger.kernel.org
> > Cc: linaro-mm-sig@lists.linaro.org
> > Cc: linux-rdma@vger.kernel.org
> > Cc: amd-gfx@lists.freedesktop.org
> > Cc: intel-gfx@lists.freedesktop.org
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Christian König <christian.koenig@amd.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > ---
> >  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > index 3584e29323c0..b3b84a0d3baf 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > @@ -2415,6 +2415,14 @@ static int amdgpu_device_ip_suspend_phase1(struct amdgpu_device *adev)
> >                 /* displays are handled separately */
> >                 if (adev->ip_blocks[i].version->type == AMD_IP_BLOCK_TYPE_DCE) {
> >                         /* XXX handle errors */
> > +
> > +                       /*
> > +                        * This is dm_suspend, which calls modeset locks, and
> > +                        * that a pretty good inversion against dma_fence_signal
> > +                        * which gpu recovery is supposed to guarantee.
> > +                        *
> > +                        * Dont ask me how to fix this.
> > +                        */
> 
> We actually have a fix for this.  Will be out shortly.

Spoilers? Solid way is to sidesteck the entire thing by avoiding to reset
the display block entirely. Fixing the locking while still resetting the
display is going to be really hard otoh ...
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch

Re: [RFC 16/17] drm/amdgpu: gpu recovery does full modesets

[Alex Deucher]

On Tue, May 12, 2020 at 8:58 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>
> On Tue, May 12, 2020 at 08:54:45AM -0400, Alex Deucher wrote:
> > On Tue, May 12, 2020 at 5:00 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > >
> > > ...
> > >
> > > I think it's time to stop this little exercise.
> > >
> > > The lockdep splat, for the record:
> > >
> > > [  132.583381] ======================================================
> > > [  132.584091] WARNING: possible circular locking dependency detected
> > > [  132.584775] 5.7.0-rc3+ #346 Tainted: G        W
> > > [  132.585461] ------------------------------------------------------
> > > [  132.586184] kworker/2:3/865 is trying to acquire lock:
> > > [  132.586857] ffffc90000677c70 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > [  132.587569]
> > >                but task is already holding lock:
> > > [  132.589044] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > > [  132.589803]
> > >                which lock already depends on the new lock.
> > >
> > > [  132.592009]
> > >                the existing dependency chain (in reverse order) is:
> > > [  132.593507]
> > >                -> #2 (dma_fence_map){++++}-{0:0}:
> > > [  132.595019]        dma_fence_begin_signalling+0x50/0x60
> > > [  132.595767]        drm_atomic_helper_commit+0xa1/0x180 [drm_kms_helper]
> > > [  132.596567]        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
> > > [  132.597420]        drm_client_modeset_commit_locked+0x55/0x190 [drm]
> > > [  132.598178]        drm_client_modeset_commit+0x24/0x40 [drm]
> > > [  132.598948]        drm_fb_helper_restore_fbdev_mode_unlocked+0x4b/0xa0 [drm_kms_helper]
> > > [  132.599738]        drm_fb_helper_set_par+0x30/0x40 [drm_kms_helper]
> > > [  132.600539]        fbcon_init+0x2e8/0x660
> > > [  132.601344]        visual_init+0xce/0x130
> > > [  132.602156]        do_bind_con_driver+0x1bc/0x2b0
> > > [  132.602970]        do_take_over_console+0x115/0x180
> > > [  132.603763]        do_fbcon_takeover+0x58/0xb0
> > > [  132.604564]        register_framebuffer+0x1ee/0x300
> > > [  132.605369]        __drm_fb_helper_initial_config_and_unlock+0x36e/0x520 [drm_kms_helper]
> > > [  132.606187]        amdgpu_fbdev_init+0xb3/0xf0 [amdgpu]
> > > [  132.607032]        amdgpu_device_init.cold+0xe90/0x1677 [amdgpu]
> > > [  132.607862]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > > [  132.608697]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > > [  132.609511]        local_pci_probe+0x42/0x80
> > > [  132.610324]        pci_device_probe+0x104/0x1a0
> > > [  132.611130]        really_probe+0x147/0x3c0
> > > [  132.611939]        driver_probe_device+0xb6/0x100
> > > [  132.612766]        device_driver_attach+0x53/0x60
> > > [  132.613593]        __driver_attach+0x8c/0x150
> > > [  132.614419]        bus_for_each_dev+0x7b/0xc0
> > > [  132.615249]        bus_add_driver+0x14c/0x1f0
> > > [  132.616071]        driver_register+0x6c/0xc0
> > > [  132.616902]        do_one_initcall+0x5d/0x2f0
> > > [  132.617731]        do_init_module+0x5c/0x230
> > > [  132.618560]        load_module+0x2981/0x2bc0
> > > [  132.619391]        __do_sys_finit_module+0xaa/0x110
> > > [  132.620228]        do_syscall_64+0x5a/0x250
> > > [  132.621064]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > > [  132.621903]
> > >                -> #1 (crtc_ww_class_mutex){+.+.}-{3:3}:
> > > [  132.623587]        __ww_mutex_lock.constprop.0+0xcc/0x10c0
> > > [  132.624448]        ww_mutex_lock+0x43/0xb0
> > > [  132.625315]        drm_modeset_lock+0x44/0x120 [drm]
> > > [  132.626184]        drmm_mode_config_init+0x2db/0x8b0 [drm]
> > > [  132.627098]        amdgpu_device_init.cold+0xbd1/0x1677 [amdgpu]
> > > [  132.628007]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > > [  132.628920]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > > [  132.629804]        local_pci_probe+0x42/0x80
> > > [  132.630690]        pci_device_probe+0x104/0x1a0
> > > [  132.631583]        really_probe+0x147/0x3c0
> > > [  132.632479]        driver_probe_device+0xb6/0x100
> > > [  132.633379]        device_driver_attach+0x53/0x60
> > > [  132.634275]        __driver_attach+0x8c/0x150
> > > [  132.635170]        bus_for_each_dev+0x7b/0xc0
> > > [  132.636069]        bus_add_driver+0x14c/0x1f0
> > > [  132.636974]        driver_register+0x6c/0xc0
> > > [  132.637870]        do_one_initcall+0x5d/0x2f0
> > > [  132.638765]        do_init_module+0x5c/0x230
> > > [  132.639654]        load_module+0x2981/0x2bc0
> > > [  132.640522]        __do_sys_finit_module+0xaa/0x110
> > > [  132.641372]        do_syscall_64+0x5a/0x250
> > > [  132.642203]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > > [  132.643022]
> > >                -> #0 (crtc_ww_class_acquire){+.+.}-{0:0}:
> > > [  132.644643]        __lock_acquire+0x1241/0x23f0
> > > [  132.645469]        lock_acquire+0xad/0x370
> > > [  132.646274]        drm_modeset_acquire_init+0xd2/0x100 [drm]
> > > [  132.647071]        drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > [  132.647902]        dm_suspend+0x1c/0x60 [amdgpu]
> > > [  132.648698]        amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > > [  132.649498]        amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > > [  132.650300]        amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > > [  132.651084]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > > [  132.651825]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > > [  132.652594]        process_one_work+0x23c/0x580
> > > [  132.653402]        worker_thread+0x50/0x3b0
> > > [  132.654139]        kthread+0x12e/0x150
> > > [  132.654868]        ret_from_fork+0x27/0x50
> > > [  132.655598]
> > >                other info that might help us debug this:
> > >
> > > [  132.657739] Chain exists of:
> > >                  crtc_ww_class_acquire --> crtc_ww_class_mutex --> dma_fence_map
> > >
> > > [  132.659877]  Possible unsafe locking scenario:
> > >
> > > [  132.661416]        CPU0                    CPU1
> > > [  132.662126]        ----                    ----
> > > [  132.662847]   lock(dma_fence_map);
> > > [  132.663574]                                lock(crtc_ww_class_mutex);
> > > [  132.664319]                                lock(dma_fence_map);
> > > [  132.665063]   lock(crtc_ww_class_acquire);
> > > [  132.665799]
> > >                 *** DEADLOCK ***
> > >
> > > [  132.667965] 4 locks held by kworker/2:3/865:
> > > [  132.668701]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > > [  132.669462]  #1: ffffc90000677e58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > > [  132.670242]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > > [  132.671039]  #3: ffff8887b84a1748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x59e/0xe64 [amdgpu]
> > > [  132.671902]
> > >                stack backtrace:
> > > [  132.673515] CPU: 2 PID: 865 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
> > > [  132.674347] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
> > > [  132.675194] Workqueue: events drm_sched_job_timedout [gpu_sched]
> > > [  132.676046] Call Trace:
> > > [  132.676897]  dump_stack+0x8f/0xd0
> > > [  132.677748]  check_noncircular+0x162/0x180
> > > [  132.678604]  ? stack_trace_save+0x4b/0x70
> > > [  132.679459]  __lock_acquire+0x1241/0x23f0
> > > [  132.680311]  lock_acquire+0xad/0x370
> > > [  132.681163]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > [  132.682021]  ? cpumask_next+0x16/0x20
> > > [  132.682880]  ? module_assert_mutex_or_preempt+0x14/0x40
> > > [  132.683737]  ? __module_address+0x28/0xf0
> > > [  132.684601]  drm_modeset_acquire_init+0xd2/0x100 [drm]
> > > [  132.685466]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > [  132.686335]  drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > [  132.687255]  dm_suspend+0x1c/0x60 [amdgpu]
> > > [  132.688152]  amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > > [  132.689057]  ? amdgpu_fence_process+0x4c/0x150 [amdgpu]
> > > [  132.689963]  amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > > [  132.690893]  amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > > [  132.691818]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > > [  132.692707]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > > [  132.693597]  process_one_work+0x23c/0x580
> > > [  132.694487]  worker_thread+0x50/0x3b0
> > > [  132.695373]  ? process_one_work+0x580/0x580
> > > [  132.696264]  kthread+0x12e/0x150
> > > [  132.697154]  ? kthread_create_worker_on_cpu+0x70/0x70
> > > [  132.698057]  ret_from_fork+0x27/0x50
> > >
> > > Cc: linux-media@vger.kernel.org
> > > Cc: linaro-mm-sig@lists.linaro.org
> > > Cc: linux-rdma@vger.kernel.org
> > > Cc: amd-gfx@lists.freedesktop.org
> > > Cc: intel-gfx@lists.freedesktop.org
> > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > > Cc: Christian König <christian.koenig@amd.com>
> > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > ---
> > >  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
> > >  1 file changed, 8 insertions(+)
> > >
> > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > index 3584e29323c0..b3b84a0d3baf 100644
> > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > @@ -2415,6 +2415,14 @@ static int amdgpu_device_ip_suspend_phase1(struct amdgpu_device *adev)
> > >                 /* displays are handled separately */
> > >                 if (adev->ip_blocks[i].version->type == AMD_IP_BLOCK_TYPE_DCE) {
> > >                         /* XXX handle errors */
> > > +
> > > +                       /*
> > > +                        * This is dm_suspend, which calls modeset locks, and
> > > +                        * that a pretty good inversion against dma_fence_signal
> > > +                        * which gpu recovery is supposed to guarantee.
> > > +                        *
> > > +                        * Dont ask me how to fix this.
> > > +                        */
> >
> > We actually have a fix for this.  Will be out shortly.
>
> Spoilers? Solid way is to sidesteck the entire thing by avoiding to reset
> the display block entirely. Fixing the locking while still resetting the
> display is going to be really hard otoh ...

There's no way to avoid that.  On dGPUs at least a full asic reset is
a full asic reset.  Mostly just skips the modeset and does the minimum
amount necessary to get the display block into a good state for reset.

Alex

> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> http://blog.ffwll.ch

Re: [RFC 16/17] drm/amdgpu: gpu recovery does full modesets

[Daniel Vetter]

On Tue, May 12, 2020 at 3:12 PM Alex Deucher <alexdeucher@gmail.com> wrote:
>
> On Tue, May 12, 2020 at 8:58 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> >
> > On Tue, May 12, 2020 at 08:54:45AM -0400, Alex Deucher wrote:
> > > On Tue, May 12, 2020 at 5:00 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > > >
> > > > ...
> > > >
> > > > I think it's time to stop this little exercise.
> > > >
> > > > The lockdep splat, for the record:
> > > >
> > > > [  132.583381] ======================================================
> > > > [  132.584091] WARNING: possible circular locking dependency detected
> > > > [  132.584775] 5.7.0-rc3+ #346 Tainted: G        W
> > > > [  132.585461] ------------------------------------------------------
> > > > [  132.586184] kworker/2:3/865 is trying to acquire lock:
> > > > [  132.586857] ffffc90000677c70 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > [  132.587569]
> > > >                but task is already holding lock:
> > > > [  132.589044] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > > > [  132.589803]
> > > >                which lock already depends on the new lock.
> > > >
> > > > [  132.592009]
> > > >                the existing dependency chain (in reverse order) is:
> > > > [  132.593507]
> > > >                -> #2 (dma_fence_map){++++}-{0:0}:
> > > > [  132.595019]        dma_fence_begin_signalling+0x50/0x60
> > > > [  132.595767]        drm_atomic_helper_commit+0xa1/0x180 [drm_kms_helper]
> > > > [  132.596567]        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
> > > > [  132.597420]        drm_client_modeset_commit_locked+0x55/0x190 [drm]
> > > > [  132.598178]        drm_client_modeset_commit+0x24/0x40 [drm]
> > > > [  132.598948]        drm_fb_helper_restore_fbdev_mode_unlocked+0x4b/0xa0 [drm_kms_helper]
> > > > [  132.599738]        drm_fb_helper_set_par+0x30/0x40 [drm_kms_helper]
> > > > [  132.600539]        fbcon_init+0x2e8/0x660
> > > > [  132.601344]        visual_init+0xce/0x130
> > > > [  132.602156]        do_bind_con_driver+0x1bc/0x2b0
> > > > [  132.602970]        do_take_over_console+0x115/0x180
> > > > [  132.603763]        do_fbcon_takeover+0x58/0xb0
> > > > [  132.604564]        register_framebuffer+0x1ee/0x300
> > > > [  132.605369]        __drm_fb_helper_initial_config_and_unlock+0x36e/0x520 [drm_kms_helper]
> > > > [  132.606187]        amdgpu_fbdev_init+0xb3/0xf0 [amdgpu]
> > > > [  132.607032]        amdgpu_device_init.cold+0xe90/0x1677 [amdgpu]
> > > > [  132.607862]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > > > [  132.608697]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > > > [  132.609511]        local_pci_probe+0x42/0x80
> > > > [  132.610324]        pci_device_probe+0x104/0x1a0
> > > > [  132.611130]        really_probe+0x147/0x3c0
> > > > [  132.611939]        driver_probe_device+0xb6/0x100
> > > > [  132.612766]        device_driver_attach+0x53/0x60
> > > > [  132.613593]        __driver_attach+0x8c/0x150
> > > > [  132.614419]        bus_for_each_dev+0x7b/0xc0
> > > > [  132.615249]        bus_add_driver+0x14c/0x1f0
> > > > [  132.616071]        driver_register+0x6c/0xc0
> > > > [  132.616902]        do_one_initcall+0x5d/0x2f0
> > > > [  132.617731]        do_init_module+0x5c/0x230
> > > > [  132.618560]        load_module+0x2981/0x2bc0
> > > > [  132.619391]        __do_sys_finit_module+0xaa/0x110
> > > > [  132.620228]        do_syscall_64+0x5a/0x250
> > > > [  132.621064]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > > > [  132.621903]
> > > >                -> #1 (crtc_ww_class_mutex){+.+.}-{3:3}:
> > > > [  132.623587]        __ww_mutex_lock.constprop.0+0xcc/0x10c0
> > > > [  132.624448]        ww_mutex_lock+0x43/0xb0
> > > > [  132.625315]        drm_modeset_lock+0x44/0x120 [drm]
> > > > [  132.626184]        drmm_mode_config_init+0x2db/0x8b0 [drm]
> > > > [  132.627098]        amdgpu_device_init.cold+0xbd1/0x1677 [amdgpu]
> > > > [  132.628007]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > > > [  132.628920]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > > > [  132.629804]        local_pci_probe+0x42/0x80
> > > > [  132.630690]        pci_device_probe+0x104/0x1a0
> > > > [  132.631583]        really_probe+0x147/0x3c0
> > > > [  132.632479]        driver_probe_device+0xb6/0x100
> > > > [  132.633379]        device_driver_attach+0x53/0x60
> > > > [  132.634275]        __driver_attach+0x8c/0x150
> > > > [  132.635170]        bus_for_each_dev+0x7b/0xc0
> > > > [  132.636069]        bus_add_driver+0x14c/0x1f0
> > > > [  132.636974]        driver_register+0x6c/0xc0
> > > > [  132.637870]        do_one_initcall+0x5d/0x2f0
> > > > [  132.638765]        do_init_module+0x5c/0x230
> > > > [  132.639654]        load_module+0x2981/0x2bc0
> > > > [  132.640522]        __do_sys_finit_module+0xaa/0x110
> > > > [  132.641372]        do_syscall_64+0x5a/0x250
> > > > [  132.642203]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > > > [  132.643022]
> > > >                -> #0 (crtc_ww_class_acquire){+.+.}-{0:0}:
> > > > [  132.644643]        __lock_acquire+0x1241/0x23f0
> > > > [  132.645469]        lock_acquire+0xad/0x370
> > > > [  132.646274]        drm_modeset_acquire_init+0xd2/0x100 [drm]
> > > > [  132.647071]        drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > [  132.647902]        dm_suspend+0x1c/0x60 [amdgpu]
> > > > [  132.648698]        amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > > > [  132.649498]        amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > > > [  132.650300]        amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > > > [  132.651084]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > > > [  132.651825]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > > > [  132.652594]        process_one_work+0x23c/0x580
> > > > [  132.653402]        worker_thread+0x50/0x3b0
> > > > [  132.654139]        kthread+0x12e/0x150
> > > > [  132.654868]        ret_from_fork+0x27/0x50
> > > > [  132.655598]
> > > >                other info that might help us debug this:
> > > >
> > > > [  132.657739] Chain exists of:
> > > >                  crtc_ww_class_acquire --> crtc_ww_class_mutex --> dma_fence_map
> > > >
> > > > [  132.659877]  Possible unsafe locking scenario:
> > > >
> > > > [  132.661416]        CPU0                    CPU1
> > > > [  132.662126]        ----                    ----
> > > > [  132.662847]   lock(dma_fence_map);
> > > > [  132.663574]                                lock(crtc_ww_class_mutex);
> > > > [  132.664319]                                lock(dma_fence_map);
> > > > [  132.665063]   lock(crtc_ww_class_acquire);
> > > > [  132.665799]
> > > >                 *** DEADLOCK ***
> > > >
> > > > [  132.667965] 4 locks held by kworker/2:3/865:
> > > > [  132.668701]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > > > [  132.669462]  #1: ffffc90000677e58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > > > [  132.670242]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > > > [  132.671039]  #3: ffff8887b84a1748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x59e/0xe64 [amdgpu]
> > > > [  132.671902]
> > > >                stack backtrace:
> > > > [  132.673515] CPU: 2 PID: 865 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
> > > > [  132.674347] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
> > > > [  132.675194] Workqueue: events drm_sched_job_timedout [gpu_sched]
> > > > [  132.676046] Call Trace:
> > > > [  132.676897]  dump_stack+0x8f/0xd0
> > > > [  132.677748]  check_noncircular+0x162/0x180
> > > > [  132.678604]  ? stack_trace_save+0x4b/0x70
> > > > [  132.679459]  __lock_acquire+0x1241/0x23f0
> > > > [  132.680311]  lock_acquire+0xad/0x370
> > > > [  132.681163]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > [  132.682021]  ? cpumask_next+0x16/0x20
> > > > [  132.682880]  ? module_assert_mutex_or_preempt+0x14/0x40
> > > > [  132.683737]  ? __module_address+0x28/0xf0
> > > > [  132.684601]  drm_modeset_acquire_init+0xd2/0x100 [drm]
> > > > [  132.685466]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > [  132.686335]  drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > [  132.687255]  dm_suspend+0x1c/0x60 [amdgpu]
> > > > [  132.688152]  amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > > > [  132.689057]  ? amdgpu_fence_process+0x4c/0x150 [amdgpu]
> > > > [  132.689963]  amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > > > [  132.690893]  amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > > > [  132.691818]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > > > [  132.692707]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > > > [  132.693597]  process_one_work+0x23c/0x580
> > > > [  132.694487]  worker_thread+0x50/0x3b0
> > > > [  132.695373]  ? process_one_work+0x580/0x580
> > > > [  132.696264]  kthread+0x12e/0x150
> > > > [  132.697154]  ? kthread_create_worker_on_cpu+0x70/0x70
> > > > [  132.698057]  ret_from_fork+0x27/0x50
> > > >
> > > > Cc: linux-media@vger.kernel.org
> > > > Cc: linaro-mm-sig@lists.linaro.org
> > > > Cc: linux-rdma@vger.kernel.org
> > > > Cc: amd-gfx@lists.freedesktop.org
> > > > Cc: intel-gfx@lists.freedesktop.org
> > > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > > > Cc: Christian König <christian.koenig@amd.com>
> > > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > > ---
> > > >  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
> > > >  1 file changed, 8 insertions(+)
> > > >
> > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > index 3584e29323c0..b3b84a0d3baf 100644
> > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > @@ -2415,6 +2415,14 @@ static int amdgpu_device_ip_suspend_phase1(struct amdgpu_device *adev)
> > > >                 /* displays are handled separately */
> > > >                 if (adev->ip_blocks[i].version->type == AMD_IP_BLOCK_TYPE_DCE) {
> > > >                         /* XXX handle errors */
> > > > +
> > > > +                       /*
> > > > +                        * This is dm_suspend, which calls modeset locks, and
> > > > +                        * that a pretty good inversion against dma_fence_signal
> > > > +                        * which gpu recovery is supposed to guarantee.
> > > > +                        *
> > > > +                        * Dont ask me how to fix this.
> > > > +                        */
> > >
> > > We actually have a fix for this.  Will be out shortly.
> >
> > Spoilers? Solid way is to sidesteck the entire thing by avoiding to reset
> > the display block entirely. Fixing the locking while still resetting the
> > display is going to be really hard otoh ...
>
> There's no way to avoid that.  On dGPUs at least a full asic reset is
> a full asic reset.  Mostly just skips the modeset and does the minimum
> amount necessary to get the display block into a good state for reset.

But how do you restore the display afterwards? "[RFC 13/17]
drm/scheduler: use dma-fence annotations in tdr work" earlier in the
series has some ideas from me for at least
some of the problems for tdr when the display gets reset along.
Whacking the display while a modeset/flip/whatever is ongoing
concurrently doesn't sound like a good idea, so not sure how you can
do that without taking the drm_modeset_locks. And once you do that,
it's deadlock time.
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 16/17] drm/amdgpu: gpu recovery does full modesets

[Alex Deucher]

On Tue, May 12, 2020 at 9:17 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>
> On Tue, May 12, 2020 at 3:12 PM Alex Deucher <alexdeucher@gmail.com> wrote:
> >
> > On Tue, May 12, 2020 at 8:58 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> > >
> > > On Tue, May 12, 2020 at 08:54:45AM -0400, Alex Deucher wrote:
> > > > On Tue, May 12, 2020 at 5:00 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > > > >
> > > > > ...
> > > > >
> > > > > I think it's time to stop this little exercise.
> > > > >
> > > > > The lockdep splat, for the record:
> > > > >
> > > > > [  132.583381] ======================================================
> > > > > [  132.584091] WARNING: possible circular locking dependency detected
> > > > > [  132.584775] 5.7.0-rc3+ #346 Tainted: G        W
> > > > > [  132.585461] ------------------------------------------------------
> > > > > [  132.586184] kworker/2:3/865 is trying to acquire lock:
> > > > > [  132.586857] ffffc90000677c70 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > [  132.587569]
> > > > >                but task is already holding lock:
> > > > > [  132.589044] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > > > > [  132.589803]
> > > > >                which lock already depends on the new lock.
> > > > >
> > > > > [  132.592009]
> > > > >                the existing dependency chain (in reverse order) is:
> > > > > [  132.593507]
> > > > >                -> #2 (dma_fence_map){++++}-{0:0}:
> > > > > [  132.595019]        dma_fence_begin_signalling+0x50/0x60
> > > > > [  132.595767]        drm_atomic_helper_commit+0xa1/0x180 [drm_kms_helper]
> > > > > [  132.596567]        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
> > > > > [  132.597420]        drm_client_modeset_commit_locked+0x55/0x190 [drm]
> > > > > [  132.598178]        drm_client_modeset_commit+0x24/0x40 [drm]
> > > > > [  132.598948]        drm_fb_helper_restore_fbdev_mode_unlocked+0x4b/0xa0 [drm_kms_helper]
> > > > > [  132.599738]        drm_fb_helper_set_par+0x30/0x40 [drm_kms_helper]
> > > > > [  132.600539]        fbcon_init+0x2e8/0x660
> > > > > [  132.601344]        visual_init+0xce/0x130
> > > > > [  132.602156]        do_bind_con_driver+0x1bc/0x2b0
> > > > > [  132.602970]        do_take_over_console+0x115/0x180
> > > > > [  132.603763]        do_fbcon_takeover+0x58/0xb0
> > > > > [  132.604564]        register_framebuffer+0x1ee/0x300
> > > > > [  132.605369]        __drm_fb_helper_initial_config_and_unlock+0x36e/0x520 [drm_kms_helper]
> > > > > [  132.606187]        amdgpu_fbdev_init+0xb3/0xf0 [amdgpu]
> > > > > [  132.607032]        amdgpu_device_init.cold+0xe90/0x1677 [amdgpu]
> > > > > [  132.607862]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > > > > [  132.608697]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > > > > [  132.609511]        local_pci_probe+0x42/0x80
> > > > > [  132.610324]        pci_device_probe+0x104/0x1a0
> > > > > [  132.611130]        really_probe+0x147/0x3c0
> > > > > [  132.611939]        driver_probe_device+0xb6/0x100
> > > > > [  132.612766]        device_driver_attach+0x53/0x60
> > > > > [  132.613593]        __driver_attach+0x8c/0x150
> > > > > [  132.614419]        bus_for_each_dev+0x7b/0xc0
> > > > > [  132.615249]        bus_add_driver+0x14c/0x1f0
> > > > > [  132.616071]        driver_register+0x6c/0xc0
> > > > > [  132.616902]        do_one_initcall+0x5d/0x2f0
> > > > > [  132.617731]        do_init_module+0x5c/0x230
> > > > > [  132.618560]        load_module+0x2981/0x2bc0
> > > > > [  132.619391]        __do_sys_finit_module+0xaa/0x110
> > > > > [  132.620228]        do_syscall_64+0x5a/0x250
> > > > > [  132.621064]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > > > > [  132.621903]
> > > > >                -> #1 (crtc_ww_class_mutex){+.+.}-{3:3}:
> > > > > [  132.623587]        __ww_mutex_lock.constprop.0+0xcc/0x10c0
> > > > > [  132.624448]        ww_mutex_lock+0x43/0xb0
> > > > > [  132.625315]        drm_modeset_lock+0x44/0x120 [drm]
> > > > > [  132.626184]        drmm_mode_config_init+0x2db/0x8b0 [drm]
> > > > > [  132.627098]        amdgpu_device_init.cold+0xbd1/0x1677 [amdgpu]
> > > > > [  132.628007]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > > > > [  132.628920]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > > > > [  132.629804]        local_pci_probe+0x42/0x80
> > > > > [  132.630690]        pci_device_probe+0x104/0x1a0
> > > > > [  132.631583]        really_probe+0x147/0x3c0
> > > > > [  132.632479]        driver_probe_device+0xb6/0x100
> > > > > [  132.633379]        device_driver_attach+0x53/0x60
> > > > > [  132.634275]        __driver_attach+0x8c/0x150
> > > > > [  132.635170]        bus_for_each_dev+0x7b/0xc0
> > > > > [  132.636069]        bus_add_driver+0x14c/0x1f0
> > > > > [  132.636974]        driver_register+0x6c/0xc0
> > > > > [  132.637870]        do_one_initcall+0x5d/0x2f0
> > > > > [  132.638765]        do_init_module+0x5c/0x230
> > > > > [  132.639654]        load_module+0x2981/0x2bc0
> > > > > [  132.640522]        __do_sys_finit_module+0xaa/0x110
> > > > > [  132.641372]        do_syscall_64+0x5a/0x250
> > > > > [  132.642203]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > > > > [  132.643022]
> > > > >                -> #0 (crtc_ww_class_acquire){+.+.}-{0:0}:
> > > > > [  132.644643]        __lock_acquire+0x1241/0x23f0
> > > > > [  132.645469]        lock_acquire+0xad/0x370
> > > > > [  132.646274]        drm_modeset_acquire_init+0xd2/0x100 [drm]
> > > > > [  132.647071]        drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > [  132.647902]        dm_suspend+0x1c/0x60 [amdgpu]
> > > > > [  132.648698]        amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > > > > [  132.649498]        amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > > > > [  132.650300]        amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > > > > [  132.651084]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > > > > [  132.651825]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > > > > [  132.652594]        process_one_work+0x23c/0x580
> > > > > [  132.653402]        worker_thread+0x50/0x3b0
> > > > > [  132.654139]        kthread+0x12e/0x150
> > > > > [  132.654868]        ret_from_fork+0x27/0x50
> > > > > [  132.655598]
> > > > >                other info that might help us debug this:
> > > > >
> > > > > [  132.657739] Chain exists of:
> > > > >                  crtc_ww_class_acquire --> crtc_ww_class_mutex --> dma_fence_map
> > > > >
> > > > > [  132.659877]  Possible unsafe locking scenario:
> > > > >
> > > > > [  132.661416]        CPU0                    CPU1
> > > > > [  132.662126]        ----                    ----
> > > > > [  132.662847]   lock(dma_fence_map);
> > > > > [  132.663574]                                lock(crtc_ww_class_mutex);
> > > > > [  132.664319]                                lock(dma_fence_map);
> > > > > [  132.665063]   lock(crtc_ww_class_acquire);
> > > > > [  132.665799]
> > > > >                 *** DEADLOCK ***
> > > > >
> > > > > [  132.667965] 4 locks held by kworker/2:3/865:
> > > > > [  132.668701]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > > > > [  132.669462]  #1: ffffc90000677e58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > > > > [  132.670242]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > > > > [  132.671039]  #3: ffff8887b84a1748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x59e/0xe64 [amdgpu]
> > > > > [  132.671902]
> > > > >                stack backtrace:
> > > > > [  132.673515] CPU: 2 PID: 865 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
> > > > > [  132.674347] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
> > > > > [  132.675194] Workqueue: events drm_sched_job_timedout [gpu_sched]
> > > > > [  132.676046] Call Trace:
> > > > > [  132.676897]  dump_stack+0x8f/0xd0
> > > > > [  132.677748]  check_noncircular+0x162/0x180
> > > > > [  132.678604]  ? stack_trace_save+0x4b/0x70
> > > > > [  132.679459]  __lock_acquire+0x1241/0x23f0
> > > > > [  132.680311]  lock_acquire+0xad/0x370
> > > > > [  132.681163]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > [  132.682021]  ? cpumask_next+0x16/0x20
> > > > > [  132.682880]  ? module_assert_mutex_or_preempt+0x14/0x40
> > > > > [  132.683737]  ? __module_address+0x28/0xf0
> > > > > [  132.684601]  drm_modeset_acquire_init+0xd2/0x100 [drm]
> > > > > [  132.685466]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > [  132.686335]  drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > [  132.687255]  dm_suspend+0x1c/0x60 [amdgpu]
> > > > > [  132.688152]  amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > > > > [  132.689057]  ? amdgpu_fence_process+0x4c/0x150 [amdgpu]
> > > > > [  132.689963]  amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > > > > [  132.690893]  amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > > > > [  132.691818]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > > > > [  132.692707]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > > > > [  132.693597]  process_one_work+0x23c/0x580
> > > > > [  132.694487]  worker_thread+0x50/0x3b0
> > > > > [  132.695373]  ? process_one_work+0x580/0x580
> > > > > [  132.696264]  kthread+0x12e/0x150
> > > > > [  132.697154]  ? kthread_create_worker_on_cpu+0x70/0x70
> > > > > [  132.698057]  ret_from_fork+0x27/0x50
> > > > >
> > > > > Cc: linux-media@vger.kernel.org
> > > > > Cc: linaro-mm-sig@lists.linaro.org
> > > > > Cc: linux-rdma@vger.kernel.org
> > > > > Cc: amd-gfx@lists.freedesktop.org
> > > > > Cc: intel-gfx@lists.freedesktop.org
> > > > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > > > > Cc: Christian König <christian.koenig@amd.com>
> > > > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > > > ---
> > > > >  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
> > > > >  1 file changed, 8 insertions(+)
> > > > >
> > > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > index 3584e29323c0..b3b84a0d3baf 100644
> > > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > @@ -2415,6 +2415,14 @@ static int amdgpu_device_ip_suspend_phase1(struct amdgpu_device *adev)
> > > > >                 /* displays are handled separately */
> > > > >                 if (adev->ip_blocks[i].version->type == AMD_IP_BLOCK_TYPE_DCE) {
> > > > >                         /* XXX handle errors */
> > > > > +
> > > > > +                       /*
> > > > > +                        * This is dm_suspend, which calls modeset locks, and
> > > > > +                        * that a pretty good inversion against dma_fence_signal
> > > > > +                        * which gpu recovery is supposed to guarantee.
> > > > > +                        *
> > > > > +                        * Dont ask me how to fix this.
> > > > > +                        */
> > > >
> > > > We actually have a fix for this.  Will be out shortly.
> > >
> > > Spoilers? Solid way is to sidesteck the entire thing by avoiding to reset
> > > the display block entirely. Fixing the locking while still resetting the
> > > display is going to be really hard otoh ...
> >
> > There's no way to avoid that.  On dGPUs at least a full asic reset is
> > a full asic reset.  Mostly just skips the modeset and does the minimum
> > amount necessary to get the display block into a good state for reset.
>
> But how do you restore the display afterwards? "[RFC 13/17]
> drm/scheduler: use dma-fence annotations in tdr work" earlier in the
> series has some ideas from me for at least
> some of the problems for tdr when the display gets reset along.
> Whacking the display while a modeset/flip/whatever is ongoing
> concurrently doesn't sound like a good idea, so not sure how you can
> do that without taking the drm_modeset_locks. And once you do that,
> it's deadlock time.

We cache the current display hw state and restore it after the reset
without going through the atomic interfaces so everything is back the
way it was before the reset.  IIRC, when we reset the reset of the
GPU, we disconnect the fences, and then re-attach them after a reset.

Alex

> -Daniel
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 16/17] drm/amdgpu: gpu recovery does full modesets

[Daniel Vetter]

On Tue, May 12, 2020 at 3:29 PM Alex Deucher <alexdeucher@gmail.com> wrote:
>
> On Tue, May 12, 2020 at 9:17 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >
> > On Tue, May 12, 2020 at 3:12 PM Alex Deucher <alexdeucher@gmail.com> wrote:
> > >
> > > On Tue, May 12, 2020 at 8:58 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> > > >
> > > > On Tue, May 12, 2020 at 08:54:45AM -0400, Alex Deucher wrote:
> > > > > On Tue, May 12, 2020 at 5:00 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > > > > >
> > > > > > ...
> > > > > >
> > > > > > I think it's time to stop this little exercise.
> > > > > >
> > > > > > The lockdep splat, for the record:
> > > > > >
> > > > > > [  132.583381] ======================================================
> > > > > > [  132.584091] WARNING: possible circular locking dependency detected
> > > > > > [  132.584775] 5.7.0-rc3+ #346 Tainted: G        W
> > > > > > [  132.585461] ------------------------------------------------------
> > > > > > [  132.586184] kworker/2:3/865 is trying to acquire lock:
> > > > > > [  132.586857] ffffc90000677c70 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > [  132.587569]
> > > > > >                but task is already holding lock:
> > > > > > [  132.589044] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > > > > > [  132.589803]
> > > > > >                which lock already depends on the new lock.
> > > > > >
> > > > > > [  132.592009]
> > > > > >                the existing dependency chain (in reverse order) is:
> > > > > > [  132.593507]
> > > > > >                -> #2 (dma_fence_map){++++}-{0:0}:
> > > > > > [  132.595019]        dma_fence_begin_signalling+0x50/0x60
> > > > > > [  132.595767]        drm_atomic_helper_commit+0xa1/0x180 [drm_kms_helper]
> > > > > > [  132.596567]        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
> > > > > > [  132.597420]        drm_client_modeset_commit_locked+0x55/0x190 [drm]
> > > > > > [  132.598178]        drm_client_modeset_commit+0x24/0x40 [drm]
> > > > > > [  132.598948]        drm_fb_helper_restore_fbdev_mode_unlocked+0x4b/0xa0 [drm_kms_helper]
> > > > > > [  132.599738]        drm_fb_helper_set_par+0x30/0x40 [drm_kms_helper]
> > > > > > [  132.600539]        fbcon_init+0x2e8/0x660
> > > > > > [  132.601344]        visual_init+0xce/0x130
> > > > > > [  132.602156]        do_bind_con_driver+0x1bc/0x2b0
> > > > > > [  132.602970]        do_take_over_console+0x115/0x180
> > > > > > [  132.603763]        do_fbcon_takeover+0x58/0xb0
> > > > > > [  132.604564]        register_framebuffer+0x1ee/0x300
> > > > > > [  132.605369]        __drm_fb_helper_initial_config_and_unlock+0x36e/0x520 [drm_kms_helper]
> > > > > > [  132.606187]        amdgpu_fbdev_init+0xb3/0xf0 [amdgpu]
> > > > > > [  132.607032]        amdgpu_device_init.cold+0xe90/0x1677 [amdgpu]
> > > > > > [  132.607862]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > > > > > [  132.608697]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > > > > > [  132.609511]        local_pci_probe+0x42/0x80
> > > > > > [  132.610324]        pci_device_probe+0x104/0x1a0
> > > > > > [  132.611130]        really_probe+0x147/0x3c0
> > > > > > [  132.611939]        driver_probe_device+0xb6/0x100
> > > > > > [  132.612766]        device_driver_attach+0x53/0x60
> > > > > > [  132.613593]        __driver_attach+0x8c/0x150
> > > > > > [  132.614419]        bus_for_each_dev+0x7b/0xc0
> > > > > > [  132.615249]        bus_add_driver+0x14c/0x1f0
> > > > > > [  132.616071]        driver_register+0x6c/0xc0
> > > > > > [  132.616902]        do_one_initcall+0x5d/0x2f0
> > > > > > [  132.617731]        do_init_module+0x5c/0x230
> > > > > > [  132.618560]        load_module+0x2981/0x2bc0
> > > > > > [  132.619391]        __do_sys_finit_module+0xaa/0x110
> > > > > > [  132.620228]        do_syscall_64+0x5a/0x250
> > > > > > [  132.621064]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > > > > > [  132.621903]
> > > > > >                -> #1 (crtc_ww_class_mutex){+.+.}-{3:3}:
> > > > > > [  132.623587]        __ww_mutex_lock.constprop.0+0xcc/0x10c0
> > > > > > [  132.624448]        ww_mutex_lock+0x43/0xb0
> > > > > > [  132.625315]        drm_modeset_lock+0x44/0x120 [drm]
> > > > > > [  132.626184]        drmm_mode_config_init+0x2db/0x8b0 [drm]
> > > > > > [  132.627098]        amdgpu_device_init.cold+0xbd1/0x1677 [amdgpu]
> > > > > > [  132.628007]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > > > > > [  132.628920]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > > > > > [  132.629804]        local_pci_probe+0x42/0x80
> > > > > > [  132.630690]        pci_device_probe+0x104/0x1a0
> > > > > > [  132.631583]        really_probe+0x147/0x3c0
> > > > > > [  132.632479]        driver_probe_device+0xb6/0x100
> > > > > > [  132.633379]        device_driver_attach+0x53/0x60
> > > > > > [  132.634275]        __driver_attach+0x8c/0x150
> > > > > > [  132.635170]        bus_for_each_dev+0x7b/0xc0
> > > > > > [  132.636069]        bus_add_driver+0x14c/0x1f0
> > > > > > [  132.636974]        driver_register+0x6c/0xc0
> > > > > > [  132.637870]        do_one_initcall+0x5d/0x2f0
> > > > > > [  132.638765]        do_init_module+0x5c/0x230
> > > > > > [  132.639654]        load_module+0x2981/0x2bc0
> > > > > > [  132.640522]        __do_sys_finit_module+0xaa/0x110
> > > > > > [  132.641372]        do_syscall_64+0x5a/0x250
> > > > > > [  132.642203]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > > > > > [  132.643022]
> > > > > >                -> #0 (crtc_ww_class_acquire){+.+.}-{0:0}:
> > > > > > [  132.644643]        __lock_acquire+0x1241/0x23f0
> > > > > > [  132.645469]        lock_acquire+0xad/0x370
> > > > > > [  132.646274]        drm_modeset_acquire_init+0xd2/0x100 [drm]
> > > > > > [  132.647071]        drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > [  132.647902]        dm_suspend+0x1c/0x60 [amdgpu]
> > > > > > [  132.648698]        amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > > > > > [  132.649498]        amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > > > > > [  132.650300]        amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > > > > > [  132.651084]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > > > > > [  132.651825]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > > > > > [  132.652594]        process_one_work+0x23c/0x580
> > > > > > [  132.653402]        worker_thread+0x50/0x3b0
> > > > > > [  132.654139]        kthread+0x12e/0x150
> > > > > > [  132.654868]        ret_from_fork+0x27/0x50
> > > > > > [  132.655598]
> > > > > >                other info that might help us debug this:
> > > > > >
> > > > > > [  132.657739] Chain exists of:
> > > > > >                  crtc_ww_class_acquire --> crtc_ww_class_mutex --> dma_fence_map
> > > > > >
> > > > > > [  132.659877]  Possible unsafe locking scenario:
> > > > > >
> > > > > > [  132.661416]        CPU0                    CPU1
> > > > > > [  132.662126]        ----                    ----
> > > > > > [  132.662847]   lock(dma_fence_map);
> > > > > > [  132.663574]                                lock(crtc_ww_class_mutex);
> > > > > > [  132.664319]                                lock(dma_fence_map);
> > > > > > [  132.665063]   lock(crtc_ww_class_acquire);
> > > > > > [  132.665799]
> > > > > >                 *** DEADLOCK ***
> > > > > >
> > > > > > [  132.667965] 4 locks held by kworker/2:3/865:
> > > > > > [  132.668701]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > > > > > [  132.669462]  #1: ffffc90000677e58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > > > > > [  132.670242]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > > > > > [  132.671039]  #3: ffff8887b84a1748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x59e/0xe64 [amdgpu]
> > > > > > [  132.671902]
> > > > > >                stack backtrace:
> > > > > > [  132.673515] CPU: 2 PID: 865 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
> > > > > > [  132.674347] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
> > > > > > [  132.675194] Workqueue: events drm_sched_job_timedout [gpu_sched]
> > > > > > [  132.676046] Call Trace:
> > > > > > [  132.676897]  dump_stack+0x8f/0xd0
> > > > > > [  132.677748]  check_noncircular+0x162/0x180
> > > > > > [  132.678604]  ? stack_trace_save+0x4b/0x70
> > > > > > [  132.679459]  __lock_acquire+0x1241/0x23f0
> > > > > > [  132.680311]  lock_acquire+0xad/0x370
> > > > > > [  132.681163]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > [  132.682021]  ? cpumask_next+0x16/0x20
> > > > > > [  132.682880]  ? module_assert_mutex_or_preempt+0x14/0x40
> > > > > > [  132.683737]  ? __module_address+0x28/0xf0
> > > > > > [  132.684601]  drm_modeset_acquire_init+0xd2/0x100 [drm]
> > > > > > [  132.685466]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > [  132.686335]  drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > [  132.687255]  dm_suspend+0x1c/0x60 [amdgpu]
> > > > > > [  132.688152]  amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > > > > > [  132.689057]  ? amdgpu_fence_process+0x4c/0x150 [amdgpu]
> > > > > > [  132.689963]  amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > > > > > [  132.690893]  amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > > > > > [  132.691818]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > > > > > [  132.692707]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > > > > > [  132.693597]  process_one_work+0x23c/0x580
> > > > > > [  132.694487]  worker_thread+0x50/0x3b0
> > > > > > [  132.695373]  ? process_one_work+0x580/0x580
> > > > > > [  132.696264]  kthread+0x12e/0x150
> > > > > > [  132.697154]  ? kthread_create_worker_on_cpu+0x70/0x70
> > > > > > [  132.698057]  ret_from_fork+0x27/0x50
> > > > > >
> > > > > > Cc: linux-media@vger.kernel.org
> > > > > > Cc: linaro-mm-sig@lists.linaro.org
> > > > > > Cc: linux-rdma@vger.kernel.org
> > > > > > Cc: amd-gfx@lists.freedesktop.org
> > > > > > Cc: intel-gfx@lists.freedesktop.org
> > > > > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > > > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > > > > > Cc: Christian König <christian.koenig@amd.com>
> > > > > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > > > > ---
> > > > > >  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
> > > > > >  1 file changed, 8 insertions(+)
> > > > > >
> > > > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > > index 3584e29323c0..b3b84a0d3baf 100644
> > > > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > > @@ -2415,6 +2415,14 @@ static int amdgpu_device_ip_suspend_phase1(struct amdgpu_device *adev)
> > > > > >                 /* displays are handled separately */
> > > > > >                 if (adev->ip_blocks[i].version->type == AMD_IP_BLOCK_TYPE_DCE) {
> > > > > >                         /* XXX handle errors */
> > > > > > +
> > > > > > +                       /*
> > > > > > +                        * This is dm_suspend, which calls modeset locks, and
> > > > > > +                        * that a pretty good inversion against dma_fence_signal
> > > > > > +                        * which gpu recovery is supposed to guarantee.
> > > > > > +                        *
> > > > > > +                        * Dont ask me how to fix this.
> > > > > > +                        */
> > > > >
> > > > > We actually have a fix for this.  Will be out shortly.
> > > >
> > > > Spoilers? Solid way is to sidesteck the entire thing by avoiding to reset
> > > > the display block entirely. Fixing the locking while still resetting the
> > > > display is going to be really hard otoh ...
> > >
> > > There's no way to avoid that.  On dGPUs at least a full asic reset is
> > > a full asic reset.  Mostly just skips the modeset and does the minimum
> > > amount necessary to get the display block into a good state for reset.
> >
> > But how do you restore the display afterwards? "[RFC 13/17]
> > drm/scheduler: use dma-fence annotations in tdr work" earlier in the
> > series has some ideas from me for at least
> > some of the problems for tdr when the display gets reset along.
> > Whacking the display while a modeset/flip/whatever is ongoing
> > concurrently doesn't sound like a good idea, so not sure how you can
> > do that without taking the drm_modeset_locks. And once you do that,
> > it's deadlock time.
>
> We cache the current display hw state and restore it after the reset
> without going through the atomic interfaces so everything is back the
> way it was before the reset.

Hm this sounds interesting ... how do you make sure a concurrent
atomic update doesn't trample over the same mmio registers while you
do that dance?

> IIRC, when we reset the reset of the
> GPU, we disconnect the fences, and then re-attach them after a reset.

Where is that code? Since I'm not sure how you can make that work
without getting stuck in another kind of deadlock in tdr. But maybe
the code has some clever trick to pull that off somehow.
-Daniel

>
> Alex
>
> > -Daniel
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > +41 (0) 79 365 57 48 - http://blog.ffwll.ch



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 16/17] drm/amdgpu: gpu recovery does full modesets

[Alex Deucher]

On Tue, May 12, 2020 at 9:45 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>
> On Tue, May 12, 2020 at 3:29 PM Alex Deucher <alexdeucher@gmail.com> wrote:
> >
> > On Tue, May 12, 2020 at 9:17 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > >
> > > On Tue, May 12, 2020 at 3:12 PM Alex Deucher <alexdeucher@gmail.com> wrote:
> > > >
> > > > On Tue, May 12, 2020 at 8:58 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> > > > >
> > > > > On Tue, May 12, 2020 at 08:54:45AM -0400, Alex Deucher wrote:
> > > > > > On Tue, May 12, 2020 at 5:00 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > > > > > >
> > > > > > > ...
> > > > > > >
> > > > > > > I think it's time to stop this little exercise.
> > > > > > >
> > > > > > > The lockdep splat, for the record:
> > > > > > >
> > > > > > > [  132.583381] ======================================================
> > > > > > > [  132.584091] WARNING: possible circular locking dependency detected
> > > > > > > [  132.584775] 5.7.0-rc3+ #346 Tainted: G        W
> > > > > > > [  132.585461] ------------------------------------------------------
> > > > > > > [  132.586184] kworker/2:3/865 is trying to acquire lock:
> > > > > > > [  132.586857] ffffc90000677c70 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > > [  132.587569]
> > > > > > >                but task is already holding lock:
> > > > > > > [  132.589044] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > > > > > > [  132.589803]
> > > > > > >                which lock already depends on the new lock.
> > > > > > >
> > > > > > > [  132.592009]
> > > > > > >                the existing dependency chain (in reverse order) is:
> > > > > > > [  132.593507]
> > > > > > >                -> #2 (dma_fence_map){++++}-{0:0}:
> > > > > > > [  132.595019]        dma_fence_begin_signalling+0x50/0x60
> > > > > > > [  132.595767]        drm_atomic_helper_commit+0xa1/0x180 [drm_kms_helper]
> > > > > > > [  132.596567]        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
> > > > > > > [  132.597420]        drm_client_modeset_commit_locked+0x55/0x190 [drm]
> > > > > > > [  132.598178]        drm_client_modeset_commit+0x24/0x40 [drm]
> > > > > > > [  132.598948]        drm_fb_helper_restore_fbdev_mode_unlocked+0x4b/0xa0 [drm_kms_helper]
> > > > > > > [  132.599738]        drm_fb_helper_set_par+0x30/0x40 [drm_kms_helper]
> > > > > > > [  132.600539]        fbcon_init+0x2e8/0x660
> > > > > > > [  132.601344]        visual_init+0xce/0x130
> > > > > > > [  132.602156]        do_bind_con_driver+0x1bc/0x2b0
> > > > > > > [  132.602970]        do_take_over_console+0x115/0x180
> > > > > > > [  132.603763]        do_fbcon_takeover+0x58/0xb0
> > > > > > > [  132.604564]        register_framebuffer+0x1ee/0x300
> > > > > > > [  132.605369]        __drm_fb_helper_initial_config_and_unlock+0x36e/0x520 [drm_kms_helper]
> > > > > > > [  132.606187]        amdgpu_fbdev_init+0xb3/0xf0 [amdgpu]
> > > > > > > [  132.607032]        amdgpu_device_init.cold+0xe90/0x1677 [amdgpu]
> > > > > > > [  132.607862]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > > > > > > [  132.608697]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > > > > > > [  132.609511]        local_pci_probe+0x42/0x80
> > > > > > > [  132.610324]        pci_device_probe+0x104/0x1a0
> > > > > > > [  132.611130]        really_probe+0x147/0x3c0
> > > > > > > [  132.611939]        driver_probe_device+0xb6/0x100
> > > > > > > [  132.612766]        device_driver_attach+0x53/0x60
> > > > > > > [  132.613593]        __driver_attach+0x8c/0x150
> > > > > > > [  132.614419]        bus_for_each_dev+0x7b/0xc0
> > > > > > > [  132.615249]        bus_add_driver+0x14c/0x1f0
> > > > > > > [  132.616071]        driver_register+0x6c/0xc0
> > > > > > > [  132.616902]        do_one_initcall+0x5d/0x2f0
> > > > > > > [  132.617731]        do_init_module+0x5c/0x230
> > > > > > > [  132.618560]        load_module+0x2981/0x2bc0
> > > > > > > [  132.619391]        __do_sys_finit_module+0xaa/0x110
> > > > > > > [  132.620228]        do_syscall_64+0x5a/0x250
> > > > > > > [  132.621064]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > > > > > > [  132.621903]
> > > > > > >                -> #1 (crtc_ww_class_mutex){+.+.}-{3:3}:
> > > > > > > [  132.623587]        __ww_mutex_lock.constprop.0+0xcc/0x10c0
> > > > > > > [  132.624448]        ww_mutex_lock+0x43/0xb0
> > > > > > > [  132.625315]        drm_modeset_lock+0x44/0x120 [drm]
> > > > > > > [  132.626184]        drmm_mode_config_init+0x2db/0x8b0 [drm]
> > > > > > > [  132.627098]        amdgpu_device_init.cold+0xbd1/0x1677 [amdgpu]
> > > > > > > [  132.628007]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > > > > > > [  132.628920]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > > > > > > [  132.629804]        local_pci_probe+0x42/0x80
> > > > > > > [  132.630690]        pci_device_probe+0x104/0x1a0
> > > > > > > [  132.631583]        really_probe+0x147/0x3c0
> > > > > > > [  132.632479]        driver_probe_device+0xb6/0x100
> > > > > > > [  132.633379]        device_driver_attach+0x53/0x60
> > > > > > > [  132.634275]        __driver_attach+0x8c/0x150
> > > > > > > [  132.635170]        bus_for_each_dev+0x7b/0xc0
> > > > > > > [  132.636069]        bus_add_driver+0x14c/0x1f0
> > > > > > > [  132.636974]        driver_register+0x6c/0xc0
> > > > > > > [  132.637870]        do_one_initcall+0x5d/0x2f0
> > > > > > > [  132.638765]        do_init_module+0x5c/0x230
> > > > > > > [  132.639654]        load_module+0x2981/0x2bc0
> > > > > > > [  132.640522]        __do_sys_finit_module+0xaa/0x110
> > > > > > > [  132.641372]        do_syscall_64+0x5a/0x250
> > > > > > > [  132.642203]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > > > > > > [  132.643022]
> > > > > > >                -> #0 (crtc_ww_class_acquire){+.+.}-{0:0}:
> > > > > > > [  132.644643]        __lock_acquire+0x1241/0x23f0
> > > > > > > [  132.645469]        lock_acquire+0xad/0x370
> > > > > > > [  132.646274]        drm_modeset_acquire_init+0xd2/0x100 [drm]
> > > > > > > [  132.647071]        drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > > [  132.647902]        dm_suspend+0x1c/0x60 [amdgpu]
> > > > > > > [  132.648698]        amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > > > > > > [  132.649498]        amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > > > > > > [  132.650300]        amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > > > > > > [  132.651084]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > > > > > > [  132.651825]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > > > > > > [  132.652594]        process_one_work+0x23c/0x580
> > > > > > > [  132.653402]        worker_thread+0x50/0x3b0
> > > > > > > [  132.654139]        kthread+0x12e/0x150
> > > > > > > [  132.654868]        ret_from_fork+0x27/0x50
> > > > > > > [  132.655598]
> > > > > > >                other info that might help us debug this:
> > > > > > >
> > > > > > > [  132.657739] Chain exists of:
> > > > > > >                  crtc_ww_class_acquire --> crtc_ww_class_mutex --> dma_fence_map
> > > > > > >
> > > > > > > [  132.659877]  Possible unsafe locking scenario:
> > > > > > >
> > > > > > > [  132.661416]        CPU0                    CPU1
> > > > > > > [  132.662126]        ----                    ----
> > > > > > > [  132.662847]   lock(dma_fence_map);
> > > > > > > [  132.663574]                                lock(crtc_ww_class_mutex);
> > > > > > > [  132.664319]                                lock(dma_fence_map);
> > > > > > > [  132.665063]   lock(crtc_ww_class_acquire);
> > > > > > > [  132.665799]
> > > > > > >                 *** DEADLOCK ***
> > > > > > >
> > > > > > > [  132.667965] 4 locks held by kworker/2:3/865:
> > > > > > > [  132.668701]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > > > > > > [  132.669462]  #1: ffffc90000677e58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > > > > > > [  132.670242]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > > > > > > [  132.671039]  #3: ffff8887b84a1748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x59e/0xe64 [amdgpu]
> > > > > > > [  132.671902]
> > > > > > >                stack backtrace:
> > > > > > > [  132.673515] CPU: 2 PID: 865 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
> > > > > > > [  132.674347] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
> > > > > > > [  132.675194] Workqueue: events drm_sched_job_timedout [gpu_sched]
> > > > > > > [  132.676046] Call Trace:
> > > > > > > [  132.676897]  dump_stack+0x8f/0xd0
> > > > > > > [  132.677748]  check_noncircular+0x162/0x180
> > > > > > > [  132.678604]  ? stack_trace_save+0x4b/0x70
> > > > > > > [  132.679459]  __lock_acquire+0x1241/0x23f0
> > > > > > > [  132.680311]  lock_acquire+0xad/0x370
> > > > > > > [  132.681163]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > > [  132.682021]  ? cpumask_next+0x16/0x20
> > > > > > > [  132.682880]  ? module_assert_mutex_or_preempt+0x14/0x40
> > > > > > > [  132.683737]  ? __module_address+0x28/0xf0
> > > > > > > [  132.684601]  drm_modeset_acquire_init+0xd2/0x100 [drm]
> > > > > > > [  132.685466]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > > [  132.686335]  drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > > [  132.687255]  dm_suspend+0x1c/0x60 [amdgpu]
> > > > > > > [  132.688152]  amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > > > > > > [  132.689057]  ? amdgpu_fence_process+0x4c/0x150 [amdgpu]
> > > > > > > [  132.689963]  amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > > > > > > [  132.690893]  amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > > > > > > [  132.691818]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > > > > > > [  132.692707]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > > > > > > [  132.693597]  process_one_work+0x23c/0x580
> > > > > > > [  132.694487]  worker_thread+0x50/0x3b0
> > > > > > > [  132.695373]  ? process_one_work+0x580/0x580
> > > > > > > [  132.696264]  kthread+0x12e/0x150
> > > > > > > [  132.697154]  ? kthread_create_worker_on_cpu+0x70/0x70
> > > > > > > [  132.698057]  ret_from_fork+0x27/0x50
> > > > > > >
> > > > > > > Cc: linux-media@vger.kernel.org
> > > > > > > Cc: linaro-mm-sig@lists.linaro.org
> > > > > > > Cc: linux-rdma@vger.kernel.org
> > > > > > > Cc: amd-gfx@lists.freedesktop.org
> > > > > > > Cc: intel-gfx@lists.freedesktop.org
> > > > > > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > > > > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > > > > > > Cc: Christian König <christian.koenig@amd.com>
> > > > > > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > > > > > ---
> > > > > > >  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
> > > > > > >  1 file changed, 8 insertions(+)
> > > > > > >
> > > > > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > > > index 3584e29323c0..b3b84a0d3baf 100644
> > > > > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > > > @@ -2415,6 +2415,14 @@ static int amdgpu_device_ip_suspend_phase1(struct amdgpu_device *adev)
> > > > > > >                 /* displays are handled separately */
> > > > > > >                 if (adev->ip_blocks[i].version->type == AMD_IP_BLOCK_TYPE_DCE) {
> > > > > > >                         /* XXX handle errors */
> > > > > > > +
> > > > > > > +                       /*
> > > > > > > +                        * This is dm_suspend, which calls modeset locks, and
> > > > > > > +                        * that a pretty good inversion against dma_fence_signal
> > > > > > > +                        * which gpu recovery is supposed to guarantee.
> > > > > > > +                        *
> > > > > > > +                        * Dont ask me how to fix this.
> > > > > > > +                        */
> > > > > >
> > > > > > We actually have a fix for this.  Will be out shortly.
> > > > >
> > > > > Spoilers? Solid way is to sidesteck the entire thing by avoiding to reset
> > > > > the display block entirely. Fixing the locking while still resetting the
> > > > > display is going to be really hard otoh ...
> > > >
> > > > There's no way to avoid that.  On dGPUs at least a full asic reset is
> > > > a full asic reset.  Mostly just skips the modeset and does the minimum
> > > > amount necessary to get the display block into a good state for reset.
> > >
> > > But how do you restore the display afterwards? "[RFC 13/17]
> > > drm/scheduler: use dma-fence annotations in tdr work" earlier in the
> > > series has some ideas from me for at least
> > > some of the problems for tdr when the display gets reset along.
> > > Whacking the display while a modeset/flip/whatever is ongoing
> > > concurrently doesn't sound like a good idea, so not sure how you can
> > > do that without taking the drm_modeset_locks. And once you do that,
> > > it's deadlock time.
> >
> > We cache the current display hw state and restore it after the reset
> > without going through the atomic interfaces so everything is back the
> > way it was before the reset.
>
> Hm this sounds interesting ... how do you make sure a concurrent
> atomic update doesn't trample over the same mmio registers while you
> do that dance?

We take the dm->dc_lock across the reset.

>
> > IIRC, when we reset the reset of the
> > GPU, we disconnect the fences, and then re-attach them after a reset.
>
> Where is that code? Since I'm not sure how you can make that work
> without getting stuck in another kind of deadlock in tdr. But maybe
> the code has some clever trick to pull that off somehow.

The GPU scheduler.  drm_sched_stop, drm_sched_resubmit_jobs, and
drm_sched_start.

Alex


> -Daniel
>
> >
> > Alex
> >
> > > -Daniel
> > > --
> > > Daniel Vetter
> > > Software Engineer, Intel Corporation
> > > +41 (0) 79 365 57 48 - http://blog.ffwll.ch
>
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 10/17] drm/amdgpu: s/GFP_KERNEL/GFP_ATOMIC in scheduler code

[Christian König]

Hui what? Of hand that doesn't looks correct to me.

Why the heck should this be an atomic context? If that's correct 
allocating memory is the least of the problems we have.

Regards,
Christian.

Am 12.05.20 um 10:59 schrieb Daniel Vetter:
> My dma-fence lockdep annotations caught an inversion because we
> allocate memory where we really shouldn't:
>
> 	kmem_cache_alloc+0x2b/0x6d0
> 	amdgpu_fence_emit+0x30/0x330 [amdgpu]
> 	amdgpu_ib_schedule+0x306/0x550 [amdgpu]
> 	amdgpu_job_run+0x10f/0x260 [amdgpu]
> 	drm_sched_main+0x1b9/0x490 [gpu_sched]
> 	kthread+0x12e/0x150
>
> Trouble right now is that lockdep only validates against GFP_FS, which
> would be good enough for shrinkers. But for mmu_notifiers we actually
> need !GFP_ATOMIC, since they can be called from any page laundering,
> even if GFP_NOFS or GFP_NOIO are set.
>
> I guess we should improve the lockdep annotations for
> fs_reclaim_acquire/release.
>
> Ofc real fix is to properly preallocate this fence and stuff it into
> the amdgpu job structure. But GFP_ATOMIC gets the lockdep splat out of
> the way.
>
> v2: Two more allocations in scheduler paths.
>
> Frist one:
>
> 	__kmalloc+0x58/0x720
> 	amdgpu_vmid_grab+0x100/0xca0 [amdgpu]
> 	amdgpu_job_dependency+0xf9/0x120 [amdgpu]
> 	drm_sched_entity_pop_job+0x3f/0x440 [gpu_sched]
> 	drm_sched_main+0xf9/0x490 [gpu_sched]
>
> Second one:
>
> 	kmem_cache_alloc+0x2b/0x6d0
> 	amdgpu_sync_fence+0x7e/0x110 [amdgpu]
> 	amdgpu_vmid_grab+0x86b/0xca0 [amdgpu]
> 	amdgpu_job_dependency+0xf9/0x120 [amdgpu]
> 	drm_sched_entity_pop_job+0x3f/0x440 [gpu_sched]
> 	drm_sched_main+0xf9/0x490 [gpu_sched]
>
> Cc: linux-media@vger.kernel.org
> Cc: linaro-mm-sig@lists.linaro.org
> Cc: linux-rdma@vger.kernel.org
> Cc: amd-gfx@lists.freedesktop.org
> Cc: intel-gfx@lists.freedesktop.org
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Christian König <christian.koenig@amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 2 +-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c   | 2 +-
>   drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c  | 2 +-
>   3 files changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> index d878fe7fee51..055b47241bb1 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> @@ -143,7 +143,7 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f,
>   	uint32_t seq;
>   	int r;
>   
> -	fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_KERNEL);
> +	fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_ATOMIC);
>   	if (fence == NULL)
>   		return -ENOMEM;
>   
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> index fe92dcd94d4a..fdcd6659f5ad 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> @@ -208,7 +208,7 @@ static int amdgpu_vmid_grab_idle(struct amdgpu_vm *vm,
>   	if (ring->vmid_wait && !dma_fence_is_signaled(ring->vmid_wait))
>   		return amdgpu_sync_fence(sync, ring->vmid_wait, false);
>   
> -	fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_KERNEL);
> +	fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_ATOMIC);
>   	if (!fences)
>   		return -ENOMEM;
>   
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> index b87ca171986a..330476cc0c86 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> @@ -168,7 +168,7 @@ int amdgpu_sync_fence(struct amdgpu_sync *sync, struct dma_fence *f,
>   	if (amdgpu_sync_add_later(sync, f, explicit))
>   		return 0;
>   
> -	e = kmem_cache_alloc(amdgpu_sync_slab, GFP_KERNEL);
> +	e = kmem_cache_alloc(amdgpu_sync_slab, GFP_ATOMIC);
>   	if (!e)
>   		return -ENOMEM;
>   

Re: [RFC 16/17] drm/amdgpu: gpu recovery does full modesets

[Daniel Vetter]

On Tue, May 12, 2020 at 4:24 PM Alex Deucher <alexdeucher@gmail.com> wrote:
>
> On Tue, May 12, 2020 at 9:45 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >
> > On Tue, May 12, 2020 at 3:29 PM Alex Deucher <alexdeucher@gmail.com> wrote:
> > >
> > > On Tue, May 12, 2020 at 9:17 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > > >
> > > > On Tue, May 12, 2020 at 3:12 PM Alex Deucher <alexdeucher@gmail.com> wrote:
> > > > >
> > > > > On Tue, May 12, 2020 at 8:58 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> > > > > >
> > > > > > On Tue, May 12, 2020 at 08:54:45AM -0400, Alex Deucher wrote:
> > > > > > > On Tue, May 12, 2020 at 5:00 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> > > > > > > >
> > > > > > > > ...
> > > > > > > >
> > > > > > > > I think it's time to stop this little exercise.
> > > > > > > >
> > > > > > > > The lockdep splat, for the record:
> > > > > > > >
> > > > > > > > [  132.583381] ======================================================
> > > > > > > > [  132.584091] WARNING: possible circular locking dependency detected
> > > > > > > > [  132.584775] 5.7.0-rc3+ #346 Tainted: G        W
> > > > > > > > [  132.585461] ------------------------------------------------------
> > > > > > > > [  132.586184] kworker/2:3/865 is trying to acquire lock:
> > > > > > > > [  132.586857] ffffc90000677c70 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > > > [  132.587569]
> > > > > > > >                but task is already holding lock:
> > > > > > > > [  132.589044] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > > > > > > > [  132.589803]
> > > > > > > >                which lock already depends on the new lock.
> > > > > > > >
> > > > > > > > [  132.592009]
> > > > > > > >                the existing dependency chain (in reverse order) is:
> > > > > > > > [  132.593507]
> > > > > > > >                -> #2 (dma_fence_map){++++}-{0:0}:
> > > > > > > > [  132.595019]        dma_fence_begin_signalling+0x50/0x60
> > > > > > > > [  132.595767]        drm_atomic_helper_commit+0xa1/0x180 [drm_kms_helper]
> > > > > > > > [  132.596567]        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
> > > > > > > > [  132.597420]        drm_client_modeset_commit_locked+0x55/0x190 [drm]
> > > > > > > > [  132.598178]        drm_client_modeset_commit+0x24/0x40 [drm]
> > > > > > > > [  132.598948]        drm_fb_helper_restore_fbdev_mode_unlocked+0x4b/0xa0 [drm_kms_helper]
> > > > > > > > [  132.599738]        drm_fb_helper_set_par+0x30/0x40 [drm_kms_helper]
> > > > > > > > [  132.600539]        fbcon_init+0x2e8/0x660
> > > > > > > > [  132.601344]        visual_init+0xce/0x130
> > > > > > > > [  132.602156]        do_bind_con_driver+0x1bc/0x2b0
> > > > > > > > [  132.602970]        do_take_over_console+0x115/0x180
> > > > > > > > [  132.603763]        do_fbcon_takeover+0x58/0xb0
> > > > > > > > [  132.604564]        register_framebuffer+0x1ee/0x300
> > > > > > > > [  132.605369]        __drm_fb_helper_initial_config_and_unlock+0x36e/0x520 [drm_kms_helper]
> > > > > > > > [  132.606187]        amdgpu_fbdev_init+0xb3/0xf0 [amdgpu]
> > > > > > > > [  132.607032]        amdgpu_device_init.cold+0xe90/0x1677 [amdgpu]
> > > > > > > > [  132.607862]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > > > > > > > [  132.608697]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > > > > > > > [  132.609511]        local_pci_probe+0x42/0x80
> > > > > > > > [  132.610324]        pci_device_probe+0x104/0x1a0
> > > > > > > > [  132.611130]        really_probe+0x147/0x3c0
> > > > > > > > [  132.611939]        driver_probe_device+0xb6/0x100
> > > > > > > > [  132.612766]        device_driver_attach+0x53/0x60
> > > > > > > > [  132.613593]        __driver_attach+0x8c/0x150
> > > > > > > > [  132.614419]        bus_for_each_dev+0x7b/0xc0
> > > > > > > > [  132.615249]        bus_add_driver+0x14c/0x1f0
> > > > > > > > [  132.616071]        driver_register+0x6c/0xc0
> > > > > > > > [  132.616902]        do_one_initcall+0x5d/0x2f0
> > > > > > > > [  132.617731]        do_init_module+0x5c/0x230
> > > > > > > > [  132.618560]        load_module+0x2981/0x2bc0
> > > > > > > > [  132.619391]        __do_sys_finit_module+0xaa/0x110
> > > > > > > > [  132.620228]        do_syscall_64+0x5a/0x250
> > > > > > > > [  132.621064]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > > > > > > > [  132.621903]
> > > > > > > >                -> #1 (crtc_ww_class_mutex){+.+.}-{3:3}:
> > > > > > > > [  132.623587]        __ww_mutex_lock.constprop.0+0xcc/0x10c0
> > > > > > > > [  132.624448]        ww_mutex_lock+0x43/0xb0
> > > > > > > > [  132.625315]        drm_modeset_lock+0x44/0x120 [drm]
> > > > > > > > [  132.626184]        drmm_mode_config_init+0x2db/0x8b0 [drm]
> > > > > > > > [  132.627098]        amdgpu_device_init.cold+0xbd1/0x1677 [amdgpu]
> > > > > > > > [  132.628007]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> > > > > > > > [  132.628920]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> > > > > > > > [  132.629804]        local_pci_probe+0x42/0x80
> > > > > > > > [  132.630690]        pci_device_probe+0x104/0x1a0
> > > > > > > > [  132.631583]        really_probe+0x147/0x3c0
> > > > > > > > [  132.632479]        driver_probe_device+0xb6/0x100
> > > > > > > > [  132.633379]        device_driver_attach+0x53/0x60
> > > > > > > > [  132.634275]        __driver_attach+0x8c/0x150
> > > > > > > > [  132.635170]        bus_for_each_dev+0x7b/0xc0
> > > > > > > > [  132.636069]        bus_add_driver+0x14c/0x1f0
> > > > > > > > [  132.636974]        driver_register+0x6c/0xc0
> > > > > > > > [  132.637870]        do_one_initcall+0x5d/0x2f0
> > > > > > > > [  132.638765]        do_init_module+0x5c/0x230
> > > > > > > > [  132.639654]        load_module+0x2981/0x2bc0
> > > > > > > > [  132.640522]        __do_sys_finit_module+0xaa/0x110
> > > > > > > > [  132.641372]        do_syscall_64+0x5a/0x250
> > > > > > > > [  132.642203]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> > > > > > > > [  132.643022]
> > > > > > > >                -> #0 (crtc_ww_class_acquire){+.+.}-{0:0}:
> > > > > > > > [  132.644643]        __lock_acquire+0x1241/0x23f0
> > > > > > > > [  132.645469]        lock_acquire+0xad/0x370
> > > > > > > > [  132.646274]        drm_modeset_acquire_init+0xd2/0x100 [drm]
> > > > > > > > [  132.647071]        drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > > > [  132.647902]        dm_suspend+0x1c/0x60 [amdgpu]
> > > > > > > > [  132.648698]        amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > > > > > > > [  132.649498]        amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > > > > > > > [  132.650300]        amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > > > > > > > [  132.651084]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > > > > > > > [  132.651825]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > > > > > > > [  132.652594]        process_one_work+0x23c/0x580
> > > > > > > > [  132.653402]        worker_thread+0x50/0x3b0
> > > > > > > > [  132.654139]        kthread+0x12e/0x150
> > > > > > > > [  132.654868]        ret_from_fork+0x27/0x50
> > > > > > > > [  132.655598]
> > > > > > > >                other info that might help us debug this:
> > > > > > > >
> > > > > > > > [  132.657739] Chain exists of:
> > > > > > > >                  crtc_ww_class_acquire --> crtc_ww_class_mutex --> dma_fence_map
> > > > > > > >
> > > > > > > > [  132.659877]  Possible unsafe locking scenario:
> > > > > > > >
> > > > > > > > [  132.661416]        CPU0                    CPU1
> > > > > > > > [  132.662126]        ----                    ----
> > > > > > > > [  132.662847]   lock(dma_fence_map);
> > > > > > > > [  132.663574]                                lock(crtc_ww_class_mutex);
> > > > > > > > [  132.664319]                                lock(dma_fence_map);
> > > > > > > > [  132.665063]   lock(crtc_ww_class_acquire);
> > > > > > > > [  132.665799]
> > > > > > > >                 *** DEADLOCK ***
> > > > > > > >
> > > > > > > > [  132.667965] 4 locks held by kworker/2:3/865:
> > > > > > > > [  132.668701]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > > > > > > > [  132.669462]  #1: ffffc90000677e58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> > > > > > > > [  132.670242]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> > > > > > > > [  132.671039]  #3: ffff8887b84a1748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x59e/0xe64 [amdgpu]
> > > > > > > > [  132.671902]
> > > > > > > >                stack backtrace:
> > > > > > > > [  132.673515] CPU: 2 PID: 865 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
> > > > > > > > [  132.674347] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
> > > > > > > > [  132.675194] Workqueue: events drm_sched_job_timedout [gpu_sched]
> > > > > > > > [  132.676046] Call Trace:
> > > > > > > > [  132.676897]  dump_stack+0x8f/0xd0
> > > > > > > > [  132.677748]  check_noncircular+0x162/0x180
> > > > > > > > [  132.678604]  ? stack_trace_save+0x4b/0x70
> > > > > > > > [  132.679459]  __lock_acquire+0x1241/0x23f0
> > > > > > > > [  132.680311]  lock_acquire+0xad/0x370
> > > > > > > > [  132.681163]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > > > [  132.682021]  ? cpumask_next+0x16/0x20
> > > > > > > > [  132.682880]  ? module_assert_mutex_or_preempt+0x14/0x40
> > > > > > > > [  132.683737]  ? __module_address+0x28/0xf0
> > > > > > > > [  132.684601]  drm_modeset_acquire_init+0xd2/0x100 [drm]
> > > > > > > > [  132.685466]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > > > [  132.686335]  drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> > > > > > > > [  132.687255]  dm_suspend+0x1c/0x60 [amdgpu]
> > > > > > > > [  132.688152]  amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> > > > > > > > [  132.689057]  ? amdgpu_fence_process+0x4c/0x150 [amdgpu]
> > > > > > > > [  132.689963]  amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> > > > > > > > [  132.690893]  amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> > > > > > > > [  132.691818]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> > > > > > > > [  132.692707]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> > > > > > > > [  132.693597]  process_one_work+0x23c/0x580
> > > > > > > > [  132.694487]  worker_thread+0x50/0x3b0
> > > > > > > > [  132.695373]  ? process_one_work+0x580/0x580
> > > > > > > > [  132.696264]  kthread+0x12e/0x150
> > > > > > > > [  132.697154]  ? kthread_create_worker_on_cpu+0x70/0x70
> > > > > > > > [  132.698057]  ret_from_fork+0x27/0x50
> > > > > > > >
> > > > > > > > Cc: linux-media@vger.kernel.org
> > > > > > > > Cc: linaro-mm-sig@lists.linaro.org
> > > > > > > > Cc: linux-rdma@vger.kernel.org
> > > > > > > > Cc: amd-gfx@lists.freedesktop.org
> > > > > > > > Cc: intel-gfx@lists.freedesktop.org
> > > > > > > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > > > > > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > > > > > > > Cc: Christian König <christian.koenig@amd.com>
> > > > > > > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > > > > > > ---
> > > > > > > >  drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
> > > > > > > >  1 file changed, 8 insertions(+)
> > > > > > > >
> > > > > > > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > > > > index 3584e29323c0..b3b84a0d3baf 100644
> > > > > > > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > > > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> > > > > > > > @@ -2415,6 +2415,14 @@ static int amdgpu_device_ip_suspend_phase1(struct amdgpu_device *adev)
> > > > > > > >                 /* displays are handled separately */
> > > > > > > >                 if (adev->ip_blocks[i].version->type == AMD_IP_BLOCK_TYPE_DCE) {
> > > > > > > >                         /* XXX handle errors */
> > > > > > > > +
> > > > > > > > +                       /*
> > > > > > > > +                        * This is dm_suspend, which calls modeset locks, and
> > > > > > > > +                        * that a pretty good inversion against dma_fence_signal
> > > > > > > > +                        * which gpu recovery is supposed to guarantee.
> > > > > > > > +                        *
> > > > > > > > +                        * Dont ask me how to fix this.
> > > > > > > > +                        */
> > > > > > >
> > > > > > > We actually have a fix for this.  Will be out shortly.
> > > > > >
> > > > > > Spoilers? Solid way is to sidesteck the entire thing by avoiding to reset
> > > > > > the display block entirely. Fixing the locking while still resetting the
> > > > > > display is going to be really hard otoh ...
> > > > >
> > > > > There's no way to avoid that.  On dGPUs at least a full asic reset is
> > > > > a full asic reset.  Mostly just skips the modeset and does the minimum
> > > > > amount necessary to get the display block into a good state for reset.
> > > >
> > > > But how do you restore the display afterwards? "[RFC 13/17]
> > > > drm/scheduler: use dma-fence annotations in tdr work" earlier in the
> > > > series has some ideas from me for at least
> > > > some of the problems for tdr when the display gets reset along.
> > > > Whacking the display while a modeset/flip/whatever is ongoing
> > > > concurrently doesn't sound like a good idea, so not sure how you can
> > > > do that without taking the drm_modeset_locks. And once you do that,
> > > > it's deadlock time.
> > >
> > > We cache the current display hw state and restore it after the reset
> > > without going through the atomic interfaces so everything is back the
> > > way it was before the reset.
> >
> > Hm this sounds interesting ... how do you make sure a concurrent
> > atomic update doesn't trample over the same mmio registers while you
> > do that dance?
>
> We take the dm->dc_lock across the reset.

Ok if that's an innermost lock and you don't do any dma_fence_wait()
while holding that (or anything that somehow depends upon that again)
I think that should work. From a quick look at current code in
drm-next that seems to be the case. But would be good to check with my
annotations whether everything is placed correctly (or maybe there's a
bug in my annotations).

I still think something like I described in the drm/scheduler patch,
which would allow us to take drm_modeset_locks in tdr path, would be a
cleaner and more robust solution longer term. Forcing drivers to do
their own modeset state looking just doesn't feel that awesome ... I
guess that also depends upon how many other drivers have this problem.

> > > IIRC, when we reset the reset of the
> > > GPU, we disconnect the fences, and then re-attach them after a reset.
> >
> > Where is that code? Since I'm not sure how you can make that work
> > without getting stuck in another kind of deadlock in tdr. But maybe
> > the code has some clever trick to pull that off somehow.
>
> The GPU scheduler.  drm_sched_stop, drm_sched_resubmit_jobs, and
> drm_sched_start.

That seems to just be about the scheduler-internal fences. That
tracking you kinda have to throw away and restart with a reset. But I
don't think these are the fences visible to other places, like in
dma_resv or drm_syncobj or wherever.
-Daniel

> Alex
>
>
> > -Daniel
> >
> > >
> > > Alex
> > >
> > > > -Daniel
> > > > --
> > > > Daniel Vetter
> > > > Software Engineer, Intel Corporation
> > > > +41 (0) 79 365 57 48 - http://blog.ffwll.ch
> >
> >
> >
> > --
> > Daniel Vetter
> > Software Engineer, Intel Corporation
> > +41 (0) 79 365 57 48 - http://blog.ffwll.ch



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 10/17] drm/amdgpu: s/GFP_KERNEL/GFP_ATOMIC in scheduler code

[Daniel Vetter]

On Tue, May 12, 2020 at 5:56 PM Christian König
<christian.koenig@amd.com> wrote:
>
> Hui what? Of hand that doesn't looks correct to me.

It's not GFP_ATOMIC, it's just that GFP_ATOMIC is the only shotgun we
have to avoid direct reclaim. And direct reclaim might need to call
into your mmu notifier, which might need to wait on a fence, which is
never going to happen because your scheduler is stuck.

Note that all the explanations for the deadlocks and stuff I'm trying
to hunt here are in the other patches, the driver ones are more
informational, so I left these here rather bare-bones to shut up
lockdep so I can get through the entire driver and all major areas
(scheduler, reset, modeset code).

Now you can do something like GFP_NOFS, but the only reasons that
works is because the direct reclaim annotations
(fs_reclaim_acquire/release) only validates against __GFP_FS, and not
against any of the other flags. We should probably add some lockdep
annotations so that __GFP_RECLAIM is annotated against the
__mmu_notifier_invalidate_range_start_map lockdep map I've recently
added for mmu notifiers. End result (assuming I'm not mixing anything
up here, this is all rather tricky stuff): GFP_ATOMIC is the only kind
of memory allocation you can do.

> Why the heck should this be an atomic context? If that's correct
> allocating memory is the least of the problems we have.

It's not about atomic, it's !__GFP_RECLAIM. Which more or less is
GFP_ATOMIC. Correct fix is probably GFP_ATOMIC + a mempool for the
scheduler fixes so that if you can't allocate them for some reason,
you at least know that your scheduler should eventually retire retire
some of them, which you can then pick up from the mempool to guarantee
forward progress.

But I really didn't dig into details of the code, this was just a quick hack.

So sleeping and taking all kinds of locks (but not all, e.g.
dma_resv_lock and drm_modeset_lock are no-go) is still totally ok.
Just think

#define GFP_NO_DIRECT_RECLAIM GFP_ATOMIC

Cheers, Daniel

>
> Regards,
> Christian.
>
> Am 12.05.20 um 10:59 schrieb Daniel Vetter:
> > My dma-fence lockdep annotations caught an inversion because we
> > allocate memory where we really shouldn't:
> >
> >       kmem_cache_alloc+0x2b/0x6d0
> >       amdgpu_fence_emit+0x30/0x330 [amdgpu]
> >       amdgpu_ib_schedule+0x306/0x550 [amdgpu]
> >       amdgpu_job_run+0x10f/0x260 [amdgpu]
> >       drm_sched_main+0x1b9/0x490 [gpu_sched]
> >       kthread+0x12e/0x150
> >
> > Trouble right now is that lockdep only validates against GFP_FS, which
> > would be good enough for shrinkers. But for mmu_notifiers we actually
> > need !GFP_ATOMIC, since they can be called from any page laundering,
> > even if GFP_NOFS or GFP_NOIO are set.
> >
> > I guess we should improve the lockdep annotations for
> > fs_reclaim_acquire/release.
> >
> > Ofc real fix is to properly preallocate this fence and stuff it into
> > the amdgpu job structure. But GFP_ATOMIC gets the lockdep splat out of
> > the way.
> >
> > v2: Two more allocations in scheduler paths.
> >
> > Frist one:
> >
> >       __kmalloc+0x58/0x720
> >       amdgpu_vmid_grab+0x100/0xca0 [amdgpu]
> >       amdgpu_job_dependency+0xf9/0x120 [amdgpu]
> >       drm_sched_entity_pop_job+0x3f/0x440 [gpu_sched]
> >       drm_sched_main+0xf9/0x490 [gpu_sched]
> >
> > Second one:
> >
> >       kmem_cache_alloc+0x2b/0x6d0
> >       amdgpu_sync_fence+0x7e/0x110 [amdgpu]
> >       amdgpu_vmid_grab+0x86b/0xca0 [amdgpu]
> >       amdgpu_job_dependency+0xf9/0x120 [amdgpu]
> >       drm_sched_entity_pop_job+0x3f/0x440 [gpu_sched]
> >       drm_sched_main+0xf9/0x490 [gpu_sched]
> >
> > Cc: linux-media@vger.kernel.org
> > Cc: linaro-mm-sig@lists.linaro.org
> > Cc: linux-rdma@vger.kernel.org
> > Cc: amd-gfx@lists.freedesktop.org
> > Cc: intel-gfx@lists.freedesktop.org
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Christian König <christian.koenig@amd.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 2 +-
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c   | 2 +-
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c  | 2 +-
> >   3 files changed, 3 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > index d878fe7fee51..055b47241bb1 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > @@ -143,7 +143,7 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f,
> >       uint32_t seq;
> >       int r;
> >
> > -     fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_KERNEL);
> > +     fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_ATOMIC);
> >       if (fence == NULL)
> >               return -ENOMEM;
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> > index fe92dcd94d4a..fdcd6659f5ad 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> > @@ -208,7 +208,7 @@ static int amdgpu_vmid_grab_idle(struct amdgpu_vm *vm,
> >       if (ring->vmid_wait && !dma_fence_is_signaled(ring->vmid_wait))
> >               return amdgpu_sync_fence(sync, ring->vmid_wait, false);
> >
> > -     fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_KERNEL);
> > +     fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_ATOMIC);
> >       if (!fences)
> >               return -ENOMEM;
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> > index b87ca171986a..330476cc0c86 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> > @@ -168,7 +168,7 @@ int amdgpu_sync_fence(struct amdgpu_sync *sync, struct dma_fence *f,
> >       if (amdgpu_sync_add_later(sync, f, explicit))
> >               return 0;
> >
> > -     e = kmem_cache_alloc(amdgpu_sync_slab, GFP_KERNEL);
> > +     e = kmem_cache_alloc(amdgpu_sync_slab, GFP_ATOMIC);
> >       if (!e)
> >               return -ENOMEM;
> >
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 10/17] drm/amdgpu: s/GFP_KERNEL/GFP_ATOMIC in scheduler code

[Daniel Vetter]

On Tue, May 12, 2020 at 6:20 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>
> On Tue, May 12, 2020 at 5:56 PM Christian König
> <christian.koenig@amd.com> wrote:
> >
> > Hui what? Of hand that doesn't looks correct to me.
>
> It's not GFP_ATOMIC, it's just that GFP_ATOMIC is the only shotgun we
> have to avoid direct reclaim. And direct reclaim might need to call
> into your mmu notifier, which might need to wait on a fence, which is
> never going to happen because your scheduler is stuck.
>
> Note that all the explanations for the deadlocks and stuff I'm trying
> to hunt here are in the other patches, the driver ones are more
> informational, so I left these here rather bare-bones to shut up
> lockdep so I can get through the entire driver and all major areas
> (scheduler, reset, modeset code).
>
> Now you can do something like GFP_NOFS, but the only reasons that
> works is because the direct reclaim annotations
> (fs_reclaim_acquire/release) only validates against __GFP_FS, and not
> against any of the other flags. We should probably add some lockdep
> annotations so that __GFP_RECLAIM is annotated against the
> __mmu_notifier_invalidate_range_start_map lockdep map I've recently
> added for mmu notifiers. End result (assuming I'm not mixing anything
> up here, this is all rather tricky stuff): GFP_ATOMIC is the only kind
> of memory allocation you can do.
>
> > Why the heck should this be an atomic context? If that's correct
> > allocating memory is the least of the problems we have.
>
> It's not about atomic, it's !__GFP_RECLAIM. Which more or less is
> GFP_ATOMIC. Correct fix is probably GFP_ATOMIC + a mempool for the
> scheduler fixes so that if you can't allocate them for some reason,
> you at least know that your scheduler should eventually retire retire
> some of them, which you can then pick up from the mempool to guarantee
> forward progress.
>
> But I really didn't dig into details of the code, this was just a quick hack.
>
> So sleeping and taking all kinds of locks (but not all, e.g.
> dma_resv_lock and drm_modeset_lock are no-go) is still totally ok.
> Just think
>
> #define GFP_NO_DIRECT_RECLAIM GFP_ATOMIC

Maybe slightly different take that's easier to understand: You've
already made the observation that anything holding adev->notifier_lock
isn't allowed to allocate memory (well GFP_ATOMIC is ok, like here).

Only thing I'm adding is that the situation is a lot worse. Plus the
lockdep annotations to help us catch these issues.
-Daniel

> Cheers, Daniel
>
> >
> > Regards,
> > Christian.
> >
> > Am 12.05.20 um 10:59 schrieb Daniel Vetter:
> > > My dma-fence lockdep annotations caught an inversion because we
> > > allocate memory where we really shouldn't:
> > >
> > >       kmem_cache_alloc+0x2b/0x6d0
> > >       amdgpu_fence_emit+0x30/0x330 [amdgpu]
> > >       amdgpu_ib_schedule+0x306/0x550 [amdgpu]
> > >       amdgpu_job_run+0x10f/0x260 [amdgpu]
> > >       drm_sched_main+0x1b9/0x490 [gpu_sched]
> > >       kthread+0x12e/0x150
> > >
> > > Trouble right now is that lockdep only validates against GFP_FS, which
> > > would be good enough for shrinkers. But for mmu_notifiers we actually
> > > need !GFP_ATOMIC, since they can be called from any page laundering,
> > > even if GFP_NOFS or GFP_NOIO are set.
> > >
> > > I guess we should improve the lockdep annotations for
> > > fs_reclaim_acquire/release.
> > >
> > > Ofc real fix is to properly preallocate this fence and stuff it into
> > > the amdgpu job structure. But GFP_ATOMIC gets the lockdep splat out of
> > > the way.
> > >
> > > v2: Two more allocations in scheduler paths.
> > >
> > > Frist one:
> > >
> > >       __kmalloc+0x58/0x720
> > >       amdgpu_vmid_grab+0x100/0xca0 [amdgpu]
> > >       amdgpu_job_dependency+0xf9/0x120 [amdgpu]
> > >       drm_sched_entity_pop_job+0x3f/0x440 [gpu_sched]
> > >       drm_sched_main+0xf9/0x490 [gpu_sched]
> > >
> > > Second one:
> > >
> > >       kmem_cache_alloc+0x2b/0x6d0
> > >       amdgpu_sync_fence+0x7e/0x110 [amdgpu]
> > >       amdgpu_vmid_grab+0x86b/0xca0 [amdgpu]
> > >       amdgpu_job_dependency+0xf9/0x120 [amdgpu]
> > >       drm_sched_entity_pop_job+0x3f/0x440 [gpu_sched]
> > >       drm_sched_main+0xf9/0x490 [gpu_sched]
> > >
> > > Cc: linux-media@vger.kernel.org
> > > Cc: linaro-mm-sig@lists.linaro.org
> > > Cc: linux-rdma@vger.kernel.org
> > > Cc: amd-gfx@lists.freedesktop.org
> > > Cc: intel-gfx@lists.freedesktop.org
> > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > > Cc: Christian König <christian.koenig@amd.com>
> > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > ---
> > >   drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 2 +-
> > >   drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c   | 2 +-
> > >   drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c  | 2 +-
> > >   3 files changed, 3 insertions(+), 3 deletions(-)
> > >
> > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > > index d878fe7fee51..055b47241bb1 100644
> > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> > > @@ -143,7 +143,7 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f,
> > >       uint32_t seq;
> > >       int r;
> > >
> > > -     fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_KERNEL);
> > > +     fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_ATOMIC);
> > >       if (fence == NULL)
> > >               return -ENOMEM;
> > >
> > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> > > index fe92dcd94d4a..fdcd6659f5ad 100644
> > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> > > @@ -208,7 +208,7 @@ static int amdgpu_vmid_grab_idle(struct amdgpu_vm *vm,
> > >       if (ring->vmid_wait && !dma_fence_is_signaled(ring->vmid_wait))
> > >               return amdgpu_sync_fence(sync, ring->vmid_wait, false);
> > >
> > > -     fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_KERNEL);
> > > +     fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_ATOMIC);
> > >       if (!fences)
> > >               return -ENOMEM;
> > >
> > > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> > > index b87ca171986a..330476cc0c86 100644
> > > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> > > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> > > @@ -168,7 +168,7 @@ int amdgpu_sync_fence(struct amdgpu_sync *sync, struct dma_fence *f,
> > >       if (amdgpu_sync_add_later(sync, f, explicit))
> > >               return 0;
> > >
> > > -     e = kmem_cache_alloc(amdgpu_sync_slab, GFP_KERNEL);
> > > +     e = kmem_cache_alloc(amdgpu_sync_slab, GFP_ATOMIC);
> > >       if (!e)
> > >               return -ENOMEM;
> > >
> >
>
>
> --
> Daniel Vetter
> Software Engineer, Intel Corporation
> +41 (0) 79 365 57 48 - http://blog.ffwll.ch



-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 10/17] drm/amdgpu: s/GFP_KERNEL/GFP_ATOMIC in scheduler code

[Christian König]

Ah!

So we can't allocate memory while scheduling anything because it could 
be that memory reclaim is waiting for the scheduler to finish pushing 
things to the hardware, right?

Indeed a nice problem, haven't noticed that one.

Christian.

Am 12.05.20 um 18:27 schrieb Daniel Vetter:
> On Tue, May 12, 2020 at 6:20 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>> On Tue, May 12, 2020 at 5:56 PM Christian König
>> <christian.koenig@amd.com> wrote:
>>> Hui what? Of hand that doesn't looks correct to me.
>> It's not GFP_ATOMIC, it's just that GFP_ATOMIC is the only shotgun we
>> have to avoid direct reclaim. And direct reclaim might need to call
>> into your mmu notifier, which might need to wait on a fence, which is
>> never going to happen because your scheduler is stuck.
>>
>> Note that all the explanations for the deadlocks and stuff I'm trying
>> to hunt here are in the other patches, the driver ones are more
>> informational, so I left these here rather bare-bones to shut up
>> lockdep so I can get through the entire driver and all major areas
>> (scheduler, reset, modeset code).
>>
>> Now you can do something like GFP_NOFS, but the only reasons that
>> works is because the direct reclaim annotations
>> (fs_reclaim_acquire/release) only validates against __GFP_FS, and not
>> against any of the other flags. We should probably add some lockdep
>> annotations so that __GFP_RECLAIM is annotated against the
>> __mmu_notifier_invalidate_range_start_map lockdep map I've recently
>> added for mmu notifiers. End result (assuming I'm not mixing anything
>> up here, this is all rather tricky stuff): GFP_ATOMIC is the only kind
>> of memory allocation you can do.
>>
>>> Why the heck should this be an atomic context? If that's correct
>>> allocating memory is the least of the problems we have.
>> It's not about atomic, it's !__GFP_RECLAIM. Which more or less is
>> GFP_ATOMIC. Correct fix is probably GFP_ATOMIC + a mempool for the
>> scheduler fixes so that if you can't allocate them for some reason,
>> you at least know that your scheduler should eventually retire retire
>> some of them, which you can then pick up from the mempool to guarantee
>> forward progress.
>>
>> But I really didn't dig into details of the code, this was just a quick hack.
>>
>> So sleeping and taking all kinds of locks (but not all, e.g.
>> dma_resv_lock and drm_modeset_lock are no-go) is still totally ok.
>> Just think
>>
>> #define GFP_NO_DIRECT_RECLAIM GFP_ATOMIC
> Maybe slightly different take that's easier to understand: You've
> already made the observation that anything holding adev->notifier_lock
> isn't allowed to allocate memory (well GFP_ATOMIC is ok, like here).
>
> Only thing I'm adding is that the situation is a lot worse. Plus the
> lockdep annotations to help us catch these issues.
> -Daniel
>
>> Cheers, Daniel
>>
>>> Regards,
>>> Christian.
>>>
>>> Am 12.05.20 um 10:59 schrieb Daniel Vetter:
>>>> My dma-fence lockdep annotations caught an inversion because we
>>>> allocate memory where we really shouldn't:
>>>>
>>>>        kmem_cache_alloc+0x2b/0x6d0
>>>>        amdgpu_fence_emit+0x30/0x330 [amdgpu]
>>>>        amdgpu_ib_schedule+0x306/0x550 [amdgpu]
>>>>        amdgpu_job_run+0x10f/0x260 [amdgpu]
>>>>        drm_sched_main+0x1b9/0x490 [gpu_sched]
>>>>        kthread+0x12e/0x150
>>>>
>>>> Trouble right now is that lockdep only validates against GFP_FS, which
>>>> would be good enough for shrinkers. But for mmu_notifiers we actually
>>>> need !GFP_ATOMIC, since they can be called from any page laundering,
>>>> even if GFP_NOFS or GFP_NOIO are set.
>>>>
>>>> I guess we should improve the lockdep annotations for
>>>> fs_reclaim_acquire/release.
>>>>
>>>> Ofc real fix is to properly preallocate this fence and stuff it into
>>>> the amdgpu job structure. But GFP_ATOMIC gets the lockdep splat out of
>>>> the way.
>>>>
>>>> v2: Two more allocations in scheduler paths.
>>>>
>>>> Frist one:
>>>>
>>>>        __kmalloc+0x58/0x720
>>>>        amdgpu_vmid_grab+0x100/0xca0 [amdgpu]
>>>>        amdgpu_job_dependency+0xf9/0x120 [amdgpu]
>>>>        drm_sched_entity_pop_job+0x3f/0x440 [gpu_sched]
>>>>        drm_sched_main+0xf9/0x490 [gpu_sched]
>>>>
>>>> Second one:
>>>>
>>>>        kmem_cache_alloc+0x2b/0x6d0
>>>>        amdgpu_sync_fence+0x7e/0x110 [amdgpu]
>>>>        amdgpu_vmid_grab+0x86b/0xca0 [amdgpu]
>>>>        amdgpu_job_dependency+0xf9/0x120 [amdgpu]
>>>>        drm_sched_entity_pop_job+0x3f/0x440 [gpu_sched]
>>>>        drm_sched_main+0xf9/0x490 [gpu_sched]
>>>>
>>>> Cc: linux-media@vger.kernel.org
>>>> Cc: linaro-mm-sig@lists.linaro.org
>>>> Cc: linux-rdma@vger.kernel.org
>>>> Cc: amd-gfx@lists.freedesktop.org
>>>> Cc: intel-gfx@lists.freedesktop.org
>>>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>>>> Cc: Christian König <christian.koenig@amd.com>
>>>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
>>>> ---
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 2 +-
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c   | 2 +-
>>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c  | 2 +-
>>>>    3 files changed, 3 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
>>>> index d878fe7fee51..055b47241bb1 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
>>>> @@ -143,7 +143,7 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f,
>>>>        uint32_t seq;
>>>>        int r;
>>>>
>>>> -     fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_KERNEL);
>>>> +     fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_ATOMIC);
>>>>        if (fence == NULL)
>>>>                return -ENOMEM;
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
>>>> index fe92dcd94d4a..fdcd6659f5ad 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
>>>> @@ -208,7 +208,7 @@ static int amdgpu_vmid_grab_idle(struct amdgpu_vm *vm,
>>>>        if (ring->vmid_wait && !dma_fence_is_signaled(ring->vmid_wait))
>>>>                return amdgpu_sync_fence(sync, ring->vmid_wait, false);
>>>>
>>>> -     fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_KERNEL);
>>>> +     fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_ATOMIC);
>>>>        if (!fences)
>>>>                return -ENOMEM;
>>>>
>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
>>>> index b87ca171986a..330476cc0c86 100644
>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
>>>> @@ -168,7 +168,7 @@ int amdgpu_sync_fence(struct amdgpu_sync *sync, struct dma_fence *f,
>>>>        if (amdgpu_sync_add_later(sync, f, explicit))
>>>>                return 0;
>>>>
>>>> -     e = kmem_cache_alloc(amdgpu_sync_slab, GFP_KERNEL);
>>>> +     e = kmem_cache_alloc(amdgpu_sync_slab, GFP_ATOMIC);
>>>>        if (!e)
>>>>                return -ENOMEM;
>>>>
>>
>> --
>> Daniel Vetter
>> Software Engineer, Intel Corporation
>> +41 (0) 79 365 57 48 - https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll.ch%2F&amp;data=02%7C01%7Cchristian.koenig%40amd.com%7C38b330b8aab946f388e908d7f691553b%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637248976369551581&amp;sdata=6rrCvEYVug95QXc3yYLbQ8ZN4wyYelfUUGWiyitVpuc%3D&amp;reserved=0
>
>

Re: [RFC 10/17] drm/amdgpu: s/GFP_KERNEL/GFP_ATOMIC in scheduler code

[Daniel Vetter]

On Tue, May 12, 2020 at 7:31 PM Christian König
<christian.koenig@amd.com> wrote:
>
> Ah!
>
> So we can't allocate memory while scheduling anything because it could
> be that memory reclaim is waiting for the scheduler to finish pushing
> things to the hardware, right?

Yup, that's my understanding. But like with all things kernel, I'm not
sure, so I tried to come up with some annotations. One of them is the
memory allocation stuff, but it also did find the modeset/dc related
issues in tdr/gpu recovery, so I think overall it's fairly sound. But
the memory side definitely needs more discussion (like really the
entire thing I'm proposing here, hence rfc).

My rough hope here is that first we figure out the exact current
semantics and nail them down in lockdep annotations and kerneldoc. And
then we need to figure out how to step-by-step land this, since lots
of drivers will have smaller and bigger issues all over.

I tried to backsearch our CI for the memory allocation issue
specifically, but unfortunately we're not retaining a whole lot of the
full logs because it's so much. But the more general issue of taking
locks somewhere in the path towards completing a fence (tail end of CS
ioctl, scheduler, tdr, modeset code since that generates fences too
for at least android, ...) that are also held while waiting for said
fences to complete is fairly common. I've seen those way too often,
and up to now lockdep is simply silent about them.

> Indeed a nice problem, haven't noticed that one.

It's pretty glorious indeed :-)

Cheers, Daniel

>
> Christian.
>
> Am 12.05.20 um 18:27 schrieb Daniel Vetter:
> > On Tue, May 12, 2020 at 6:20 PM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >> On Tue, May 12, 2020 at 5:56 PM Christian König
> >> <christian.koenig@amd.com> wrote:
> >>> Hui what? Of hand that doesn't looks correct to me.
> >> It's not GFP_ATOMIC, it's just that GFP_ATOMIC is the only shotgun we
> >> have to avoid direct reclaim. And direct reclaim might need to call
> >> into your mmu notifier, which might need to wait on a fence, which is
> >> never going to happen because your scheduler is stuck.
> >>
> >> Note that all the explanations for the deadlocks and stuff I'm trying
> >> to hunt here are in the other patches, the driver ones are more
> >> informational, so I left these here rather bare-bones to shut up
> >> lockdep so I can get through the entire driver and all major areas
> >> (scheduler, reset, modeset code).
> >>
> >> Now you can do something like GFP_NOFS, but the only reasons that
> >> works is because the direct reclaim annotations
> >> (fs_reclaim_acquire/release) only validates against __GFP_FS, and not
> >> against any of the other flags. We should probably add some lockdep
> >> annotations so that __GFP_RECLAIM is annotated against the
> >> __mmu_notifier_invalidate_range_start_map lockdep map I've recently
> >> added for mmu notifiers. End result (assuming I'm not mixing anything
> >> up here, this is all rather tricky stuff): GFP_ATOMIC is the only kind
> >> of memory allocation you can do.
> >>
> >>> Why the heck should this be an atomic context? If that's correct
> >>> allocating memory is the least of the problems we have.
> >> It's not about atomic, it's !__GFP_RECLAIM. Which more or less is
> >> GFP_ATOMIC. Correct fix is probably GFP_ATOMIC + a mempool for the
> >> scheduler fixes so that if you can't allocate them for some reason,
> >> you at least know that your scheduler should eventually retire retire
> >> some of them, which you can then pick up from the mempool to guarantee
> >> forward progress.
> >>
> >> But I really didn't dig into details of the code, this was just a quick hack.
> >>
> >> So sleeping and taking all kinds of locks (but not all, e.g.
> >> dma_resv_lock and drm_modeset_lock are no-go) is still totally ok.
> >> Just think
> >>
> >> #define GFP_NO_DIRECT_RECLAIM GFP_ATOMIC
> > Maybe slightly different take that's easier to understand: You've
> > already made the observation that anything holding adev->notifier_lock
> > isn't allowed to allocate memory (well GFP_ATOMIC is ok, like here).
> >
> > Only thing I'm adding is that the situation is a lot worse. Plus the
> > lockdep annotations to help us catch these issues.
> > -Daniel
> >
> >> Cheers, Daniel
> >>
> >>> Regards,
> >>> Christian.
> >>>
> >>> Am 12.05.20 um 10:59 schrieb Daniel Vetter:
> >>>> My dma-fence lockdep annotations caught an inversion because we
> >>>> allocate memory where we really shouldn't:
> >>>>
> >>>>        kmem_cache_alloc+0x2b/0x6d0
> >>>>        amdgpu_fence_emit+0x30/0x330 [amdgpu]
> >>>>        amdgpu_ib_schedule+0x306/0x550 [amdgpu]
> >>>>        amdgpu_job_run+0x10f/0x260 [amdgpu]
> >>>>        drm_sched_main+0x1b9/0x490 [gpu_sched]
> >>>>        kthread+0x12e/0x150
> >>>>
> >>>> Trouble right now is that lockdep only validates against GFP_FS, which
> >>>> would be good enough for shrinkers. But for mmu_notifiers we actually
> >>>> need !GFP_ATOMIC, since they can be called from any page laundering,
> >>>> even if GFP_NOFS or GFP_NOIO are set.
> >>>>
> >>>> I guess we should improve the lockdep annotations for
> >>>> fs_reclaim_acquire/release.
> >>>>
> >>>> Ofc real fix is to properly preallocate this fence and stuff it into
> >>>> the amdgpu job structure. But GFP_ATOMIC gets the lockdep splat out of
> >>>> the way.
> >>>>
> >>>> v2: Two more allocations in scheduler paths.
> >>>>
> >>>> Frist one:
> >>>>
> >>>>        __kmalloc+0x58/0x720
> >>>>        amdgpu_vmid_grab+0x100/0xca0 [amdgpu]
> >>>>        amdgpu_job_dependency+0xf9/0x120 [amdgpu]
> >>>>        drm_sched_entity_pop_job+0x3f/0x440 [gpu_sched]
> >>>>        drm_sched_main+0xf9/0x490 [gpu_sched]
> >>>>
> >>>> Second one:
> >>>>
> >>>>        kmem_cache_alloc+0x2b/0x6d0
> >>>>        amdgpu_sync_fence+0x7e/0x110 [amdgpu]
> >>>>        amdgpu_vmid_grab+0x86b/0xca0 [amdgpu]
> >>>>        amdgpu_job_dependency+0xf9/0x120 [amdgpu]
> >>>>        drm_sched_entity_pop_job+0x3f/0x440 [gpu_sched]
> >>>>        drm_sched_main+0xf9/0x490 [gpu_sched]
> >>>>
> >>>> Cc: linux-media@vger.kernel.org
> >>>> Cc: linaro-mm-sig@lists.linaro.org
> >>>> Cc: linux-rdma@vger.kernel.org
> >>>> Cc: amd-gfx@lists.freedesktop.org
> >>>> Cc: intel-gfx@lists.freedesktop.org
> >>>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> >>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >>>> Cc: Christian König <christian.koenig@amd.com>
> >>>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> >>>> ---
> >>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c | 2 +-
> >>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c   | 2 +-
> >>>>    drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c  | 2 +-
> >>>>    3 files changed, 3 insertions(+), 3 deletions(-)
> >>>>
> >>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> >>>> index d878fe7fee51..055b47241bb1 100644
> >>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> >>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_fence.c
> >>>> @@ -143,7 +143,7 @@ int amdgpu_fence_emit(struct amdgpu_ring *ring, struct dma_fence **f,
> >>>>        uint32_t seq;
> >>>>        int r;
> >>>>
> >>>> -     fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_KERNEL);
> >>>> +     fence = kmem_cache_alloc(amdgpu_fence_slab, GFP_ATOMIC);
> >>>>        if (fence == NULL)
> >>>>                return -ENOMEM;
> >>>>
> >>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> >>>> index fe92dcd94d4a..fdcd6659f5ad 100644
> >>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> >>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ids.c
> >>>> @@ -208,7 +208,7 @@ static int amdgpu_vmid_grab_idle(struct amdgpu_vm *vm,
> >>>>        if (ring->vmid_wait && !dma_fence_is_signaled(ring->vmid_wait))
> >>>>                return amdgpu_sync_fence(sync, ring->vmid_wait, false);
> >>>>
> >>>> -     fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_KERNEL);
> >>>> +     fences = kmalloc_array(sizeof(void *), id_mgr->num_ids, GFP_ATOMIC);
> >>>>        if (!fences)
> >>>>                return -ENOMEM;
> >>>>
> >>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> >>>> index b87ca171986a..330476cc0c86 100644
> >>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> >>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_sync.c
> >>>> @@ -168,7 +168,7 @@ int amdgpu_sync_fence(struct amdgpu_sync *sync, struct dma_fence *f,
> >>>>        if (amdgpu_sync_add_later(sync, f, explicit))
> >>>>                return 0;
> >>>>
> >>>> -     e = kmem_cache_alloc(amdgpu_sync_slab, GFP_KERNEL);
> >>>> +     e = kmem_cache_alloc(amdgpu_sync_slab, GFP_ATOMIC);
> >>>>        if (!e)
> >>>>                return -ENOMEM;
> >>>>
> >>
> >> --
> >> Daniel Vetter
> >> Software Engineer, Intel Corporation
> >> +41 (0) 79 365 57 48 - https://nam11.safelinks.protection.outlook.com/?url=http%3A%2F%2Fblog.ffwll.ch%2F&amp;data=02%7C01%7Cchristian.koenig%40amd.com%7C38b330b8aab946f388e908d7f691553b%7C3dd8961fe4884e608e11a82d994e183d%7C0%7C0%7C637248976369551581&amp;sdata=6rrCvEYVug95QXc3yYLbQ8ZN4wyYelfUUGWiyitVpuc%3D&amp;reserved=0
> >
> >
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 16/17] drm/amdgpu: gpu recovery does full modesets

[Kazlauskas, Nicholas]

On 2020-05-12 12:12 p.m., Daniel Vetter wrote:
> On Tue, May 12, 2020 at 4:24 PM Alex Deucher <alexdeucher@gmail.com> wrote:
>>
>> On Tue, May 12, 2020 at 9:45 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>>>
>>> On Tue, May 12, 2020 at 3:29 PM Alex Deucher <alexdeucher@gmail.com> wrote:
>>>>
>>>> On Tue, May 12, 2020 at 9:17 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>>>>>
>>>>> On Tue, May 12, 2020 at 3:12 PM Alex Deucher <alexdeucher@gmail.com> wrote:
>>>>>>
>>>>>> On Tue, May 12, 2020 at 8:58 AM Daniel Vetter <daniel@ffwll.ch> wrote:
>>>>>>>
>>>>>>> On Tue, May 12, 2020 at 08:54:45AM -0400, Alex Deucher wrote:
>>>>>>>> On Tue, May 12, 2020 at 5:00 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>>>>>>>>>
>>>>>>>>> ...
>>>>>>>>>
>>>>>>>>> I think it's time to stop this little exercise.
>>>>>>>>>
>>>>>>>>> The lockdep splat, for the record:
>>>>>>>>>
>>>>>>>>> [  132.583381] ======================================================
>>>>>>>>> [  132.584091] WARNING: possible circular locking dependency detected
>>>>>>>>> [  132.584775] 5.7.0-rc3+ #346 Tainted: G        W
>>>>>>>>> [  132.585461] ------------------------------------------------------
>>>>>>>>> [  132.586184] kworker/2:3/865 is trying to acquire lock:
>>>>>>>>> [  132.586857] ffffc90000677c70 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
>>>>>>>>> [  132.587569]
>>>>>>>>>                 but task is already holding lock:
>>>>>>>>> [  132.589044] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
>>>>>>>>> [  132.589803]
>>>>>>>>>                 which lock already depends on the new lock.
>>>>>>>>>
>>>>>>>>> [  132.592009]
>>>>>>>>>                 the existing dependency chain (in reverse order) is:
>>>>>>>>> [  132.593507]
>>>>>>>>>                 -> #2 (dma_fence_map){++++}-{0:0}:
>>>>>>>>> [  132.595019]        dma_fence_begin_signalling+0x50/0x60
>>>>>>>>> [  132.595767]        drm_atomic_helper_commit+0xa1/0x180 [drm_kms_helper]
>>>>>>>>> [  132.596567]        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
>>>>>>>>> [  132.597420]        drm_client_modeset_commit_locked+0x55/0x190 [drm]
>>>>>>>>> [  132.598178]        drm_client_modeset_commit+0x24/0x40 [drm]
>>>>>>>>> [  132.598948]        drm_fb_helper_restore_fbdev_mode_unlocked+0x4b/0xa0 [drm_kms_helper]
>>>>>>>>> [  132.599738]        drm_fb_helper_set_par+0x30/0x40 [drm_kms_helper]
>>>>>>>>> [  132.600539]        fbcon_init+0x2e8/0x660
>>>>>>>>> [  132.601344]        visual_init+0xce/0x130
>>>>>>>>> [  132.602156]        do_bind_con_driver+0x1bc/0x2b0
>>>>>>>>> [  132.602970]        do_take_over_console+0x115/0x180
>>>>>>>>> [  132.603763]        do_fbcon_takeover+0x58/0xb0
>>>>>>>>> [  132.604564]        register_framebuffer+0x1ee/0x300
>>>>>>>>> [  132.605369]        __drm_fb_helper_initial_config_and_unlock+0x36e/0x520 [drm_kms_helper]
>>>>>>>>> [  132.606187]        amdgpu_fbdev_init+0xb3/0xf0 [amdgpu]
>>>>>>>>> [  132.607032]        amdgpu_device_init.cold+0xe90/0x1677 [amdgpu]
>>>>>>>>> [  132.607862]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
>>>>>>>>> [  132.608697]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
>>>>>>>>> [  132.609511]        local_pci_probe+0x42/0x80
>>>>>>>>> [  132.610324]        pci_device_probe+0x104/0x1a0
>>>>>>>>> [  132.611130]        really_probe+0x147/0x3c0
>>>>>>>>> [  132.611939]        driver_probe_device+0xb6/0x100
>>>>>>>>> [  132.612766]        device_driver_attach+0x53/0x60
>>>>>>>>> [  132.613593]        __driver_attach+0x8c/0x150
>>>>>>>>> [  132.614419]        bus_for_each_dev+0x7b/0xc0
>>>>>>>>> [  132.615249]        bus_add_driver+0x14c/0x1f0
>>>>>>>>> [  132.616071]        driver_register+0x6c/0xc0
>>>>>>>>> [  132.616902]        do_one_initcall+0x5d/0x2f0
>>>>>>>>> [  132.617731]        do_init_module+0x5c/0x230
>>>>>>>>> [  132.618560]        load_module+0x2981/0x2bc0
>>>>>>>>> [  132.619391]        __do_sys_finit_module+0xaa/0x110
>>>>>>>>> [  132.620228]        do_syscall_64+0x5a/0x250
>>>>>>>>> [  132.621064]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
>>>>>>>>> [  132.621903]
>>>>>>>>>                 -> #1 (crtc_ww_class_mutex){+.+.}-{3:3}:
>>>>>>>>> [  132.623587]        __ww_mutex_lock.constprop.0+0xcc/0x10c0
>>>>>>>>> [  132.624448]        ww_mutex_lock+0x43/0xb0
>>>>>>>>> [  132.625315]        drm_modeset_lock+0x44/0x120 [drm]
>>>>>>>>> [  132.626184]        drmm_mode_config_init+0x2db/0x8b0 [drm]
>>>>>>>>> [  132.627098]        amdgpu_device_init.cold+0xbd1/0x1677 [amdgpu]
>>>>>>>>> [  132.628007]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
>>>>>>>>> [  132.628920]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
>>>>>>>>> [  132.629804]        local_pci_probe+0x42/0x80
>>>>>>>>> [  132.630690]        pci_device_probe+0x104/0x1a0
>>>>>>>>> [  132.631583]        really_probe+0x147/0x3c0
>>>>>>>>> [  132.632479]        driver_probe_device+0xb6/0x100
>>>>>>>>> [  132.633379]        device_driver_attach+0x53/0x60
>>>>>>>>> [  132.634275]        __driver_attach+0x8c/0x150
>>>>>>>>> [  132.635170]        bus_for_each_dev+0x7b/0xc0
>>>>>>>>> [  132.636069]        bus_add_driver+0x14c/0x1f0
>>>>>>>>> [  132.636974]        driver_register+0x6c/0xc0
>>>>>>>>> [  132.637870]        do_one_initcall+0x5d/0x2f0
>>>>>>>>> [  132.638765]        do_init_module+0x5c/0x230
>>>>>>>>> [  132.639654]        load_module+0x2981/0x2bc0
>>>>>>>>> [  132.640522]        __do_sys_finit_module+0xaa/0x110
>>>>>>>>> [  132.641372]        do_syscall_64+0x5a/0x250
>>>>>>>>> [  132.642203]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
>>>>>>>>> [  132.643022]
>>>>>>>>>                 -> #0 (crtc_ww_class_acquire){+.+.}-{0:0}:
>>>>>>>>> [  132.644643]        __lock_acquire+0x1241/0x23f0
>>>>>>>>> [  132.645469]        lock_acquire+0xad/0x370
>>>>>>>>> [  132.646274]        drm_modeset_acquire_init+0xd2/0x100 [drm]
>>>>>>>>> [  132.647071]        drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
>>>>>>>>> [  132.647902]        dm_suspend+0x1c/0x60 [amdgpu]
>>>>>>>>> [  132.648698]        amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
>>>>>>>>> [  132.649498]        amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
>>>>>>>>> [  132.650300]        amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
>>>>>>>>> [  132.651084]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
>>>>>>>>> [  132.651825]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
>>>>>>>>> [  132.652594]        process_one_work+0x23c/0x580
>>>>>>>>> [  132.653402]        worker_thread+0x50/0x3b0
>>>>>>>>> [  132.654139]        kthread+0x12e/0x150
>>>>>>>>> [  132.654868]        ret_from_fork+0x27/0x50
>>>>>>>>> [  132.655598]
>>>>>>>>>                 other info that might help us debug this:
>>>>>>>>>
>>>>>>>>> [  132.657739] Chain exists of:
>>>>>>>>>                   crtc_ww_class_acquire --> crtc_ww_class_mutex --> dma_fence_map
>>>>>>>>>
>>>>>>>>> [  132.659877]  Possible unsafe locking scenario:
>>>>>>>>>
>>>>>>>>> [  132.661416]        CPU0                    CPU1
>>>>>>>>> [  132.662126]        ----                    ----
>>>>>>>>> [  132.662847]   lock(dma_fence_map);
>>>>>>>>> [  132.663574]                                lock(crtc_ww_class_mutex);
>>>>>>>>> [  132.664319]                                lock(dma_fence_map);
>>>>>>>>> [  132.665063]   lock(crtc_ww_class_acquire);
>>>>>>>>> [  132.665799]
>>>>>>>>>                  *** DEADLOCK ***
>>>>>>>>>
>>>>>>>>> [  132.667965] 4 locks held by kworker/2:3/865:
>>>>>>>>> [  132.668701]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
>>>>>>>>> [  132.669462]  #1: ffffc90000677e58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
>>>>>>>>> [  132.670242]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
>>>>>>>>> [  132.671039]  #3: ffff8887b84a1748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x59e/0xe64 [amdgpu]
>>>>>>>>> [  132.671902]
>>>>>>>>>                 stack backtrace:
>>>>>>>>> [  132.673515] CPU: 2 PID: 865 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
>>>>>>>>> [  132.674347] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
>>>>>>>>> [  132.675194] Workqueue: events drm_sched_job_timedout [gpu_sched]
>>>>>>>>> [  132.676046] Call Trace:
>>>>>>>>> [  132.676897]  dump_stack+0x8f/0xd0
>>>>>>>>> [  132.677748]  check_noncircular+0x162/0x180
>>>>>>>>> [  132.678604]  ? stack_trace_save+0x4b/0x70
>>>>>>>>> [  132.679459]  __lock_acquire+0x1241/0x23f0
>>>>>>>>> [  132.680311]  lock_acquire+0xad/0x370
>>>>>>>>> [  132.681163]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
>>>>>>>>> [  132.682021]  ? cpumask_next+0x16/0x20
>>>>>>>>> [  132.682880]  ? module_assert_mutex_or_preempt+0x14/0x40
>>>>>>>>> [  132.683737]  ? __module_address+0x28/0xf0
>>>>>>>>> [  132.684601]  drm_modeset_acquire_init+0xd2/0x100 [drm]
>>>>>>>>> [  132.685466]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
>>>>>>>>> [  132.686335]  drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
>>>>>>>>> [  132.687255]  dm_suspend+0x1c/0x60 [amdgpu]
>>>>>>>>> [  132.688152]  amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
>>>>>>>>> [  132.689057]  ? amdgpu_fence_process+0x4c/0x150 [amdgpu]
>>>>>>>>> [  132.689963]  amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
>>>>>>>>> [  132.690893]  amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
>>>>>>>>> [  132.691818]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
>>>>>>>>> [  132.692707]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
>>>>>>>>> [  132.693597]  process_one_work+0x23c/0x580
>>>>>>>>> [  132.694487]  worker_thread+0x50/0x3b0
>>>>>>>>> [  132.695373]  ? process_one_work+0x580/0x580
>>>>>>>>> [  132.696264]  kthread+0x12e/0x150
>>>>>>>>> [  132.697154]  ? kthread_create_worker_on_cpu+0x70/0x70
>>>>>>>>> [  132.698057]  ret_from_fork+0x27/0x50
>>>>>>>>>
>>>>>>>>> Cc: linux-media@vger.kernel.org
>>>>>>>>> Cc: linaro-mm-sig@lists.linaro.org
>>>>>>>>> Cc: linux-rdma@vger.kernel.org
>>>>>>>>> Cc: amd-gfx@lists.freedesktop.org
>>>>>>>>> Cc: intel-gfx@lists.freedesktop.org
>>>>>>>>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>>>>>>>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>>>>>>>>> Cc: Christian König <christian.koenig@amd.com>
>>>>>>>>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
>>>>>>>>> ---
>>>>>>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
>>>>>>>>>   1 file changed, 8 insertions(+)
>>>>>>>>>
>>>>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>>>>>> index 3584e29323c0..b3b84a0d3baf 100644
>>>>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
>>>>>>>>> @@ -2415,6 +2415,14 @@ static int amdgpu_device_ip_suspend_phase1(struct amdgpu_device *adev)
>>>>>>>>>                  /* displays are handled separately */
>>>>>>>>>                  if (adev->ip_blocks[i].version->type == AMD_IP_BLOCK_TYPE_DCE) {
>>>>>>>>>                          /* XXX handle errors */
>>>>>>>>> +
>>>>>>>>> +                       /*
>>>>>>>>> +                        * This is dm_suspend, which calls modeset locks, and
>>>>>>>>> +                        * that a pretty good inversion against dma_fence_signal
>>>>>>>>> +                        * which gpu recovery is supposed to guarantee.
>>>>>>>>> +                        *
>>>>>>>>> +                        * Dont ask me how to fix this.
>>>>>>>>> +                        */
>>>>>>>>
>>>>>>>> We actually have a fix for this.  Will be out shortly.
>>>>>>>
>>>>>>> Spoilers? Solid way is to sidesteck the entire thing by avoiding to reset
>>>>>>> the display block entirely. Fixing the locking while still resetting the
>>>>>>> display is going to be really hard otoh ...
>>>>>>
>>>>>> There's no way to avoid that.  On dGPUs at least a full asic reset is
>>>>>> a full asic reset.  Mostly just skips the modeset and does the minimum
>>>>>> amount necessary to get the display block into a good state for reset.
>>>>>
>>>>> But how do you restore the display afterwards? "[RFC 13/17]
>>>>> drm/scheduler: use dma-fence annotations in tdr work" earlier in the
>>>>> series has some ideas from me for at least
>>>>> some of the problems for tdr when the display gets reset along.
>>>>> Whacking the display while a modeset/flip/whatever is ongoing
>>>>> concurrently doesn't sound like a good idea, so not sure how you can
>>>>> do that without taking the drm_modeset_locks. And once you do that,
>>>>> it's deadlock time.
>>>>
>>>> We cache the current display hw state and restore it after the reset
>>>> without going through the atomic interfaces so everything is back the
>>>> way it was before the reset.
>>>
>>> Hm this sounds interesting ... how do you make sure a concurrent
>>> atomic update doesn't trample over the same mmio registers while you
>>> do that dance?
>>
>> We take the dm->dc_lock across the reset.
> 
> Ok if that's an innermost lock and you don't do any dma_fence_wait()
> while holding that (or anything that somehow depends upon that again)
> I think that should work. From a quick look at current code in
> drm-next that seems to be the case. But would be good to check with my
> annotations whether everything is placed correctly (or maybe there's a
> bug in my annotations).
> 
> I still think something like I described in the drm/scheduler patch,
> which would allow us to take drm_modeset_locks in tdr path, would be a
> cleaner and more robust solution longer term. Forcing drivers to do
> their own modeset state looking just doesn't feel that awesome ... I
> guess that also depends upon how many other drivers have this problem.
> 

I worked a bit on analyzing the original problem faced here with using 
our regular dm_suspend/dm_resume here for GPU reset and I'm not sure how 
taking the drm_modeset_locks really buys us anything.

We ran into a deadlock caused by an async pageflip commit coming in 
along with the TDR suspend commit and the async commit wanted the 
dma_fence associated with the plane. The tdr commit suspend commit then 
started waiting for the pageflip commit to finish - which never happens 
since the fence hasn't been signaled yet and DRM spins forever.

If the dma_fence is "force" signaled in suspend then the async commit 
continues and the suspend commit follows after as normal. The async 
commit no longer holds any of the DRM locks because atomic_commit has 
already finished - we had no trouble grabbing the locks for the tdr commit.

Force signaling the fence wasn't really an option for solving this issue 
though, and DRM doesn't support aborting atomic commits nor would most 
drivers be well equipped to handle this I think - it's no longer really 
atomic at that point.

Ideally we don't actually have that pageflip commit programmed during 
the TDR since we'll have to reapply that same state again after, so what 
we're stuck with is the solution that we're planning on putting into 
driver - hold the internal driver locks across the suspend/reset so 
there's no way for the pageflip commit to start processing after having 
its fence signaled.

We're essentially just faking that the state is the exact same as it was 
before the GPU reset process started.

I'm open to suggestions or improvements for handling this but the 
easiest solution seemed to just bypass the entire DRM stack under the hood.

Regards,
Nicholas Kazlauskas

>>>> IIRC, when we reset the reset of the
>>>> GPU, we disconnect the fences, and then re-attach them after a reset.
>>>
>>> Where is that code? Since I'm not sure how you can make that work
>>> without getting stuck in another kind of deadlock in tdr. But maybe
>>> the code has some clever trick to pull that off somehow.
>>
>> The GPU scheduler.  drm_sched_stop, drm_sched_resubmit_jobs, and
>> drm_sched_start.
> 
> That seems to just be about the scheduler-internal fences. That
> tracking you kinda have to throw away and restart with a reset. But I
> don't think these are the fences visible to other places, like in
> dma_resv or drm_syncobj or wherever.
> -Daniel
> 
>> Alex
>>
>>
>>> -Daniel
>>>
>>>>
>>>> Alex
>>>>
>>>>> -Daniel
>>>>> --
>>>>> Daniel Vetter
>>>>> Software Engineer, Intel Corporation
>>>>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch/
>>>
>>>
>>>
>>> --
>>> Daniel Vetter
>>> Software Engineer, Intel Corporation
>>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch/
> 
> 
> 

Re: [RFC 16/17] drm/amdgpu: gpu recovery does full modesets

[Daniel Vetter]

On Tue, May 12, 2020 at 10:10 PM Kazlauskas, Nicholas
<nicholas.kazlauskas@amd.com> wrote:
>
> On 2020-05-12 12:12 p.m., Daniel Vetter wrote:
> > On Tue, May 12, 2020 at 4:24 PM Alex Deucher <alexdeucher@gmail.com> wrote:
> >>
> >> On Tue, May 12, 2020 at 9:45 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >>>
> >>> On Tue, May 12, 2020 at 3:29 PM Alex Deucher <alexdeucher@gmail.com> wrote:
> >>>>
> >>>> On Tue, May 12, 2020 at 9:17 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >>>>>
> >>>>> On Tue, May 12, 2020 at 3:12 PM Alex Deucher <alexdeucher@gmail.com> wrote:
> >>>>>>
> >>>>>> On Tue, May 12, 2020 at 8:58 AM Daniel Vetter <daniel@ffwll.ch> wrote:
> >>>>>>>
> >>>>>>> On Tue, May 12, 2020 at 08:54:45AM -0400, Alex Deucher wrote:
> >>>>>>>> On Tue, May 12, 2020 at 5:00 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
> >>>>>>>>>
> >>>>>>>>> ...
> >>>>>>>>>
> >>>>>>>>> I think it's time to stop this little exercise.
> >>>>>>>>>
> >>>>>>>>> The lockdep splat, for the record:
> >>>>>>>>>
> >>>>>>>>> [  132.583381] ======================================================
> >>>>>>>>> [  132.584091] WARNING: possible circular locking dependency detected
> >>>>>>>>> [  132.584775] 5.7.0-rc3+ #346 Tainted: G        W
> >>>>>>>>> [  132.585461] ------------------------------------------------------
> >>>>>>>>> [  132.586184] kworker/2:3/865 is trying to acquire lock:
> >>>>>>>>> [  132.586857] ffffc90000677c70 (crtc_ww_class_acquire){+.+.}-{0:0}, at: drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> >>>>>>>>> [  132.587569]
> >>>>>>>>>                 but task is already holding lock:
> >>>>>>>>> [  132.589044] ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> >>>>>>>>> [  132.589803]
> >>>>>>>>>                 which lock already depends on the new lock.
> >>>>>>>>>
> >>>>>>>>> [  132.592009]
> >>>>>>>>>                 the existing dependency chain (in reverse order) is:
> >>>>>>>>> [  132.593507]
> >>>>>>>>>                 -> #2 (dma_fence_map){++++}-{0:0}:
> >>>>>>>>> [  132.595019]        dma_fence_begin_signalling+0x50/0x60
> >>>>>>>>> [  132.595767]        drm_atomic_helper_commit+0xa1/0x180 [drm_kms_helper]
> >>>>>>>>> [  132.596567]        drm_client_modeset_commit_atomic+0x1ea/0x250 [drm]
> >>>>>>>>> [  132.597420]        drm_client_modeset_commit_locked+0x55/0x190 [drm]
> >>>>>>>>> [  132.598178]        drm_client_modeset_commit+0x24/0x40 [drm]
> >>>>>>>>> [  132.598948]        drm_fb_helper_restore_fbdev_mode_unlocked+0x4b/0xa0 [drm_kms_helper]
> >>>>>>>>> [  132.599738]        drm_fb_helper_set_par+0x30/0x40 [drm_kms_helper]
> >>>>>>>>> [  132.600539]        fbcon_init+0x2e8/0x660
> >>>>>>>>> [  132.601344]        visual_init+0xce/0x130
> >>>>>>>>> [  132.602156]        do_bind_con_driver+0x1bc/0x2b0
> >>>>>>>>> [  132.602970]        do_take_over_console+0x115/0x180
> >>>>>>>>> [  132.603763]        do_fbcon_takeover+0x58/0xb0
> >>>>>>>>> [  132.604564]        register_framebuffer+0x1ee/0x300
> >>>>>>>>> [  132.605369]        __drm_fb_helper_initial_config_and_unlock+0x36e/0x520 [drm_kms_helper]
> >>>>>>>>> [  132.606187]        amdgpu_fbdev_init+0xb3/0xf0 [amdgpu]
> >>>>>>>>> [  132.607032]        amdgpu_device_init.cold+0xe90/0x1677 [amdgpu]
> >>>>>>>>> [  132.607862]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> >>>>>>>>> [  132.608697]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> >>>>>>>>> [  132.609511]        local_pci_probe+0x42/0x80
> >>>>>>>>> [  132.610324]        pci_device_probe+0x104/0x1a0
> >>>>>>>>> [  132.611130]        really_probe+0x147/0x3c0
> >>>>>>>>> [  132.611939]        driver_probe_device+0xb6/0x100
> >>>>>>>>> [  132.612766]        device_driver_attach+0x53/0x60
> >>>>>>>>> [  132.613593]        __driver_attach+0x8c/0x150
> >>>>>>>>> [  132.614419]        bus_for_each_dev+0x7b/0xc0
> >>>>>>>>> [  132.615249]        bus_add_driver+0x14c/0x1f0
> >>>>>>>>> [  132.616071]        driver_register+0x6c/0xc0
> >>>>>>>>> [  132.616902]        do_one_initcall+0x5d/0x2f0
> >>>>>>>>> [  132.617731]        do_init_module+0x5c/0x230
> >>>>>>>>> [  132.618560]        load_module+0x2981/0x2bc0
> >>>>>>>>> [  132.619391]        __do_sys_finit_module+0xaa/0x110
> >>>>>>>>> [  132.620228]        do_syscall_64+0x5a/0x250
> >>>>>>>>> [  132.621064]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> >>>>>>>>> [  132.621903]
> >>>>>>>>>                 -> #1 (crtc_ww_class_mutex){+.+.}-{3:3}:
> >>>>>>>>> [  132.623587]        __ww_mutex_lock.constprop.0+0xcc/0x10c0
> >>>>>>>>> [  132.624448]        ww_mutex_lock+0x43/0xb0
> >>>>>>>>> [  132.625315]        drm_modeset_lock+0x44/0x120 [drm]
> >>>>>>>>> [  132.626184]        drmm_mode_config_init+0x2db/0x8b0 [drm]
> >>>>>>>>> [  132.627098]        amdgpu_device_init.cold+0xbd1/0x1677 [amdgpu]
> >>>>>>>>> [  132.628007]        amdgpu_driver_load_kms+0x5a/0x200 [amdgpu]
> >>>>>>>>> [  132.628920]        amdgpu_pci_probe+0xf7/0x180 [amdgpu]
> >>>>>>>>> [  132.629804]        local_pci_probe+0x42/0x80
> >>>>>>>>> [  132.630690]        pci_device_probe+0x104/0x1a0
> >>>>>>>>> [  132.631583]        really_probe+0x147/0x3c0
> >>>>>>>>> [  132.632479]        driver_probe_device+0xb6/0x100
> >>>>>>>>> [  132.633379]        device_driver_attach+0x53/0x60
> >>>>>>>>> [  132.634275]        __driver_attach+0x8c/0x150
> >>>>>>>>> [  132.635170]        bus_for_each_dev+0x7b/0xc0
> >>>>>>>>> [  132.636069]        bus_add_driver+0x14c/0x1f0
> >>>>>>>>> [  132.636974]        driver_register+0x6c/0xc0
> >>>>>>>>> [  132.637870]        do_one_initcall+0x5d/0x2f0
> >>>>>>>>> [  132.638765]        do_init_module+0x5c/0x230
> >>>>>>>>> [  132.639654]        load_module+0x2981/0x2bc0
> >>>>>>>>> [  132.640522]        __do_sys_finit_module+0xaa/0x110
> >>>>>>>>> [  132.641372]        do_syscall_64+0x5a/0x250
> >>>>>>>>> [  132.642203]        entry_SYSCALL_64_after_hwframe+0x49/0xb3
> >>>>>>>>> [  132.643022]
> >>>>>>>>>                 -> #0 (crtc_ww_class_acquire){+.+.}-{0:0}:
> >>>>>>>>> [  132.644643]        __lock_acquire+0x1241/0x23f0
> >>>>>>>>> [  132.645469]        lock_acquire+0xad/0x370
> >>>>>>>>> [  132.646274]        drm_modeset_acquire_init+0xd2/0x100 [drm]
> >>>>>>>>> [  132.647071]        drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> >>>>>>>>> [  132.647902]        dm_suspend+0x1c/0x60 [amdgpu]
> >>>>>>>>> [  132.648698]        amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> >>>>>>>>> [  132.649498]        amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> >>>>>>>>> [  132.650300]        amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> >>>>>>>>> [  132.651084]        amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> >>>>>>>>> [  132.651825]        drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> >>>>>>>>> [  132.652594]        process_one_work+0x23c/0x580
> >>>>>>>>> [  132.653402]        worker_thread+0x50/0x3b0
> >>>>>>>>> [  132.654139]        kthread+0x12e/0x150
> >>>>>>>>> [  132.654868]        ret_from_fork+0x27/0x50
> >>>>>>>>> [  132.655598]
> >>>>>>>>>                 other info that might help us debug this:
> >>>>>>>>>
> >>>>>>>>> [  132.657739] Chain exists of:
> >>>>>>>>>                   crtc_ww_class_acquire --> crtc_ww_class_mutex --> dma_fence_map
> >>>>>>>>>
> >>>>>>>>> [  132.659877]  Possible unsafe locking scenario:
> >>>>>>>>>
> >>>>>>>>> [  132.661416]        CPU0                    CPU1
> >>>>>>>>> [  132.662126]        ----                    ----
> >>>>>>>>> [  132.662847]   lock(dma_fence_map);
> >>>>>>>>> [  132.663574]                                lock(crtc_ww_class_mutex);
> >>>>>>>>> [  132.664319]                                lock(dma_fence_map);
> >>>>>>>>> [  132.665063]   lock(crtc_ww_class_acquire);
> >>>>>>>>> [  132.665799]
> >>>>>>>>>                  *** DEADLOCK ***
> >>>>>>>>>
> >>>>>>>>> [  132.667965] 4 locks held by kworker/2:3/865:
> >>>>>>>>> [  132.668701]  #0: ffff8887fb81c938 ((wq_completion)events){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> >>>>>>>>> [  132.669462]  #1: ffffc90000677e58 ((work_completion)(&(&sched->work_tdr)->work)){+.+.}-{0:0}, at: process_one_work+0x1bc/0x580
> >>>>>>>>> [  132.670242]  #2: ffffffff82318c80 (dma_fence_map){++++}-{0:0}, at: drm_sched_job_timedout+0x25/0xf0 [gpu_sched]
> >>>>>>>>> [  132.671039]  #3: ffff8887b84a1748 (&adev->lock_reset){+.+.}-{3:3}, at: amdgpu_device_gpu_recover.cold+0x59e/0xe64 [amdgpu]
> >>>>>>>>> [  132.671902]
> >>>>>>>>>                 stack backtrace:
> >>>>>>>>> [  132.673515] CPU: 2 PID: 865 Comm: kworker/2:3 Tainted: G        W         5.7.0-rc3+ #346
> >>>>>>>>> [  132.674347] Hardware name: System manufacturer System Product Name/PRIME X370-PRO, BIOS 4011 04/19/2018
> >>>>>>>>> [  132.675194] Workqueue: events drm_sched_job_timedout [gpu_sched]
> >>>>>>>>> [  132.676046] Call Trace:
> >>>>>>>>> [  132.676897]  dump_stack+0x8f/0xd0
> >>>>>>>>> [  132.677748]  check_noncircular+0x162/0x180
> >>>>>>>>> [  132.678604]  ? stack_trace_save+0x4b/0x70
> >>>>>>>>> [  132.679459]  __lock_acquire+0x1241/0x23f0
> >>>>>>>>> [  132.680311]  lock_acquire+0xad/0x370
> >>>>>>>>> [  132.681163]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> >>>>>>>>> [  132.682021]  ? cpumask_next+0x16/0x20
> >>>>>>>>> [  132.682880]  ? module_assert_mutex_or_preempt+0x14/0x40
> >>>>>>>>> [  132.683737]  ? __module_address+0x28/0xf0
> >>>>>>>>> [  132.684601]  drm_modeset_acquire_init+0xd2/0x100 [drm]
> >>>>>>>>> [  132.685466]  ? drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> >>>>>>>>> [  132.686335]  drm_atomic_helper_suspend+0x38/0x120 [drm_kms_helper]
> >>>>>>>>> [  132.687255]  dm_suspend+0x1c/0x60 [amdgpu]
> >>>>>>>>> [  132.688152]  amdgpu_device_ip_suspend_phase1+0x83/0xe0 [amdgpu]
> >>>>>>>>> [  132.689057]  ? amdgpu_fence_process+0x4c/0x150 [amdgpu]
> >>>>>>>>> [  132.689963]  amdgpu_device_ip_suspend+0x1c/0x60 [amdgpu]
> >>>>>>>>> [  132.690893]  amdgpu_device_gpu_recover.cold+0x4e6/0xe64 [amdgpu]
> >>>>>>>>> [  132.691818]  amdgpu_job_timedout+0xfb/0x150 [amdgpu]
> >>>>>>>>> [  132.692707]  drm_sched_job_timedout+0x8a/0xf0 [gpu_sched]
> >>>>>>>>> [  132.693597]  process_one_work+0x23c/0x580
> >>>>>>>>> [  132.694487]  worker_thread+0x50/0x3b0
> >>>>>>>>> [  132.695373]  ? process_one_work+0x580/0x580
> >>>>>>>>> [  132.696264]  kthread+0x12e/0x150
> >>>>>>>>> [  132.697154]  ? kthread_create_worker_on_cpu+0x70/0x70
> >>>>>>>>> [  132.698057]  ret_from_fork+0x27/0x50
> >>>>>>>>>
> >>>>>>>>> Cc: linux-media@vger.kernel.org
> >>>>>>>>> Cc: linaro-mm-sig@lists.linaro.org
> >>>>>>>>> Cc: linux-rdma@vger.kernel.org
> >>>>>>>>> Cc: amd-gfx@lists.freedesktop.org
> >>>>>>>>> Cc: intel-gfx@lists.freedesktop.org
> >>>>>>>>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> >>>>>>>>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> >>>>>>>>> Cc: Christian König <christian.koenig@amd.com>
> >>>>>>>>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> >>>>>>>>> ---
> >>>>>>>>>   drivers/gpu/drm/amd/amdgpu/amdgpu_device.c | 8 ++++++++
> >>>>>>>>>   1 file changed, 8 insertions(+)
> >>>>>>>>>
> >>>>>>>>> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >>>>>>>>> index 3584e29323c0..b3b84a0d3baf 100644
> >>>>>>>>> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >>>>>>>>> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_device.c
> >>>>>>>>> @@ -2415,6 +2415,14 @@ static int amdgpu_device_ip_suspend_phase1(struct amdgpu_device *adev)
> >>>>>>>>>                  /* displays are handled separately */
> >>>>>>>>>                  if (adev->ip_blocks[i].version->type == AMD_IP_BLOCK_TYPE_DCE) {
> >>>>>>>>>                          /* XXX handle errors */
> >>>>>>>>> +
> >>>>>>>>> +                       /*
> >>>>>>>>> +                        * This is dm_suspend, which calls modeset locks, and
> >>>>>>>>> +                        * that a pretty good inversion against dma_fence_signal
> >>>>>>>>> +                        * which gpu recovery is supposed to guarantee.
> >>>>>>>>> +                        *
> >>>>>>>>> +                        * Dont ask me how to fix this.
> >>>>>>>>> +                        */
> >>>>>>>>
> >>>>>>>> We actually have a fix for this.  Will be out shortly.
> >>>>>>>
> >>>>>>> Spoilers? Solid way is to sidesteck the entire thing by avoiding to reset
> >>>>>>> the display block entirely. Fixing the locking while still resetting the
> >>>>>>> display is going to be really hard otoh ...
> >>>>>>
> >>>>>> There's no way to avoid that.  On dGPUs at least a full asic reset is
> >>>>>> a full asic reset.  Mostly just skips the modeset and does the minimum
> >>>>>> amount necessary to get the display block into a good state for reset.
> >>>>>
> >>>>> But how do you restore the display afterwards? "[RFC 13/17]
> >>>>> drm/scheduler: use dma-fence annotations in tdr work" earlier in the
> >>>>> series has some ideas from me for at least
> >>>>> some of the problems for tdr when the display gets reset along.
> >>>>> Whacking the display while a modeset/flip/whatever is ongoing
> >>>>> concurrently doesn't sound like a good idea, so not sure how you can
> >>>>> do that without taking the drm_modeset_locks. And once you do that,
> >>>>> it's deadlock time.
> >>>>
> >>>> We cache the current display hw state and restore it after the reset
> >>>> without going through the atomic interfaces so everything is back the
> >>>> way it was before the reset.
> >>>
> >>> Hm this sounds interesting ... how do you make sure a concurrent
> >>> atomic update doesn't trample over the same mmio registers while you
> >>> do that dance?
> >>
> >> We take the dm->dc_lock across the reset.
> >
> > Ok if that's an innermost lock and you don't do any dma_fence_wait()
> > while holding that (or anything that somehow depends upon that again)
> > I think that should work. From a quick look at current code in
> > drm-next that seems to be the case. But would be good to check with my
> > annotations whether everything is placed correctly (or maybe there's a
> > bug in my annotations).
> >
> > I still think something like I described in the drm/scheduler patch,
> > which would allow us to take drm_modeset_locks in tdr path, would be a
> > cleaner and more robust solution longer term. Forcing drivers to do
> > their own modeset state looking just doesn't feel that awesome ... I
> > guess that also depends upon how many other drivers have this problem.
> >
>
> I worked a bit on analyzing the original problem faced here with using
> our regular dm_suspend/dm_resume here for GPU reset and I'm not sure how
> taking the drm_modeset_locks really buys us anything.
>
> We ran into a deadlock caused by an async pageflip commit coming in
> along with the TDR suspend commit and the async commit wanted the
> dma_fence associated with the plane. The tdr commit suspend commit then
> started waiting for the pageflip commit to finish - which never happens
> since the fence hasn't been signaled yet and DRM spins forever.
>
> If the dma_fence is "force" signaled in suspend then the async commit
> continues and the suspend commit follows after as normal. The async
> commit no longer holds any of the DRM locks because atomic_commit has
> already finished - we had no trouble grabbing the locks for the tdr commit.
>
> Force signaling the fence wasn't really an option for solving this issue
> though, and DRM doesn't support aborting atomic commits nor would most
> drivers be well equipped to handle this I think - it's no longer really
> atomic at that point.
>
> Ideally we don't actually have that pageflip commit programmed during
> the TDR since we'll have to reapply that same state again after, so what
> we're stuck with is the solution that we're planning on putting into
> driver - hold the internal driver locks across the suspend/reset so
> there's no way for the pageflip commit to start processing after having
> its fence signaled.
>
> We're essentially just faking that the state is the exact same as it was
> before the GPU reset process started.
>
> I'm open to suggestions or improvements for handling this but the
> easiest solution seemed to just bypass the entire DRM stack under the hood.

Yeah gets the job done, plus aside from the locks should also avoid
the memory allocations (which I also think are no-go, but much harder
to hit). The downside is that it's all custom code, plus you need that
internal lock (not really needed in atomic drivers, not sure why you
had that to begin with), and if we have a pile of other drivers which
have the same problem, might be worth fixing this in helpers itself.
One idea I sketched is here:

https://patchwork.freedesktop.org/patch/365335/?series=77179&rev=1

But it's incomplete and probably not the best one.

Cheers, Daniel


>
> Regards,
> Nicholas Kazlauskas
>
> >>>> IIRC, when we reset the reset of the
> >>>> GPU, we disconnect the fences, and then re-attach them after a reset.
> >>>
> >>> Where is that code? Since I'm not sure how you can make that work
> >>> without getting stuck in another kind of deadlock in tdr. But maybe
> >>> the code has some clever trick to pull that off somehow.
> >>
> >> The GPU scheduler.  drm_sched_stop, drm_sched_resubmit_jobs, and
> >> drm_sched_start.
> >
> > That seems to just be about the scheduler-internal fences. That
> > tracking you kinda have to throw away and restart with a reset. But I
> > don't think these are the fences visible to other places, like in
> > dma_resv or drm_syncobj or wherever.
> > -Daniel
> >
> >> Alex
> >>
> >>
> >>> -Daniel
> >>>
> >>>>
> >>>> Alex
> >>>>
> >>>>> -Daniel
> >>>>> --
> >>>>> Daniel Vetter
> >>>>> Software Engineer, Intel Corporation
> >>>>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch/
> >>>
> >>>
> >>>
> >>> --
> >>> Daniel Vetter
> >>> Software Engineer, Intel Corporation
> >>> +41 (0) 79 365 57 48 - http://blog.ffwll.ch/
> >
> >
> >
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 09/17] drm/amdgpu: use dma-fence annotations in cs_submit()

[Christian König]

Am 12.05.20 um 10:59 schrieb Daniel Vetter:
> This is a bit tricky, since ->notifier_lock is held while calling
> dma_fence_wait we must ensure that also the read side (i.e.
> dma_fence_begin_signalling) is on the same side. If we mix this up
> lockdep complaints, and that's again why we want to have these
> annotations.
>
> A nice side effect of this is that because of the fs_reclaim priming
> for dma_fence_enable lockdep now automatically checks for us that
> nothing in here allocates memory, without even running any userptr
> workloads.
>
> Cc: linux-media@vger.kernel.org
> Cc: linaro-mm-sig@lists.linaro.org
> Cc: linux-rdma@vger.kernel.org
> Cc: amd-gfx@lists.freedesktop.org
> Cc: intel-gfx@lists.freedesktop.org
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Christian König <christian.koenig@amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
>   drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 5 +++++
>   1 file changed, 5 insertions(+)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> index 7653f62b1b2d..6db3f3c629b0 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> @@ -1213,6 +1213,7 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
>   	struct amdgpu_job *job;
>   	uint64_t seq;
>   	int r;
> +	bool fence_cookie;
>   
>   	job = p->job;
>   	p->job = NULL;
> @@ -1227,6 +1228,8 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
>   	 */
>   	mutex_lock(&p->adev->notifier_lock);
>   
> +	fence_cookie = dma_fence_begin_signalling();
> +
>   	/* If userptr are invalidated after amdgpu_cs_parser_bos(), return
>   	 * -EAGAIN, drmIoctl in libdrm will restart the amdgpu_cs_ioctl.
>   	 */
> @@ -1264,12 +1267,14 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
>   	amdgpu_vm_move_to_lru_tail(p->adev, &fpriv->vm);
>   
>   	ttm_eu_fence_buffer_objects(&p->ticket, &p->validated, p->fence);
> +	dma_fence_end_signalling(fence_cookie);

Mhm, this could come earlier in theory. E.g. after pushing the job to 
the scheduler.

Christian.

>   	mutex_unlock(&p->adev->notifier_lock);
>   
>   	return 0;
>   
>   error_abort:
>   	drm_sched_job_cleanup(&job->base);
> +	dma_fence_end_signalling(fence_cookie);
>   	mutex_unlock(&p->adev->notifier_lock);
>   
>   error_unlock:

Re: [RFC 09/17] drm/amdgpu: use dma-fence annotations in cs_submit()

[Daniel Vetter]

On Wed, May 13, 2020 at 9:02 AM Christian König
<ckoenig.leichtzumerken@gmail.com> wrote:
>
> Am 12.05.20 um 10:59 schrieb Daniel Vetter:
> > This is a bit tricky, since ->notifier_lock is held while calling
> > dma_fence_wait we must ensure that also the read side (i.e.
> > dma_fence_begin_signalling) is on the same side. If we mix this up
> > lockdep complaints, and that's again why we want to have these
> > annotations.
> >
> > A nice side effect of this is that because of the fs_reclaim priming
> > for dma_fence_enable lockdep now automatically checks for us that
> > nothing in here allocates memory, without even running any userptr
> > workloads.
> >
> > Cc: linux-media@vger.kernel.org
> > Cc: linaro-mm-sig@lists.linaro.org
> > Cc: linux-rdma@vger.kernel.org
> > Cc: amd-gfx@lists.freedesktop.org
> > Cc: intel-gfx@lists.freedesktop.org
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Christian König <christian.koenig@amd.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c | 5 +++++
> >   1 file changed, 5 insertions(+)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> > index 7653f62b1b2d..6db3f3c629b0 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_cs.c
> > @@ -1213,6 +1213,7 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
> >       struct amdgpu_job *job;
> >       uint64_t seq;
> >       int r;
> > +     bool fence_cookie;
> >
> >       job = p->job;
> >       p->job = NULL;
> > @@ -1227,6 +1228,8 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
> >        */
> >       mutex_lock(&p->adev->notifier_lock);
> >
> > +     fence_cookie = dma_fence_begin_signalling();
> > +
> >       /* If userptr are invalidated after amdgpu_cs_parser_bos(), return
> >        * -EAGAIN, drmIoctl in libdrm will restart the amdgpu_cs_ioctl.
> >        */
> > @@ -1264,12 +1267,14 @@ static int amdgpu_cs_submit(struct amdgpu_cs_parser *p,
> >       amdgpu_vm_move_to_lru_tail(p->adev, &fpriv->vm);
> >
> >       ttm_eu_fence_buffer_objects(&p->ticket, &p->validated, p->fence);
> > +     dma_fence_end_signalling(fence_cookie);
>
> Mhm, this could come earlier in theory. E.g. after pushing the job to
> the scheduler.

Yeah, I have not much clue about how amdgpu works :-) In practice it
doesn't matter much, since the enclosing adev->notifier_lock is a lot
more strict about what it allows than the dma_fence signalling fake
lock.
-Daniel

>
> Christian.
>
> >       mutex_unlock(&p->adev->notifier_lock);
> >
> >       return 0;
> >
> >   error_abort:
> >       drm_sched_job_cleanup(&job->base);
> > +     dma_fence_end_signalling(fence_cookie);
> >       mutex_unlock(&p->adev->notifier_lock);
> >
> >   error_unlock:
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 02/17] dma-fence: basic lockdep annotations

[Daniel Vetter]

On Tue, May 12, 2020 at 11:19 AM Chris Wilson <chris@chris-wilson.co.uk> wrote:
> Quoting Daniel Vetter (2020-05-12 10:08:47)
> > On Tue, May 12, 2020 at 10:04:22AM +0100, Chris Wilson wrote:
> > > Quoting Daniel Vetter (2020-05-12 09:59:29)
> > > > Design is similar to the lockdep annotations for workers, but with
> > > > some twists:
> > > >
> > > > - We use a read-lock for the execution/worker/completion side, so that
> > > >   this explicit annotation can be more liberally sprinkled around.
> > > >   With read locks lockdep isn't going to complain if the read-side
> > > >   isn't nested the same way under all circumstances, so ABBA deadlocks
> > > >   are ok. Which they are, since this is an annotation only.
> > > >
> > > > - We're using non-recursive lockdep read lock mode, since in recursive
> > > >   read lock mode lockdep does not catch read side hazards. And we
> > > >   _very_ much want read side hazards to be caught. For full details of
> > > >   this limitation see
> > > >
> > > >   commit e91498589746065e3ae95d9a00b068e525eec34f
> > > >   Author: Peter Zijlstra <peterz@infradead.org>
> > > >   Date:   Wed Aug 23 13:13:11 2017 +0200
> > > >
> > > >       locking/lockdep/selftests: Add mixed read-write ABBA tests
> > > >
> > > > - To allow nesting of the read-side explicit annotations we explicitly
> > > >   keep track of the nesting. lock_is_held() allows us to do that.
> > > >
> > > > - The wait-side annotation is a write lock, and entirely done within
> > > >   dma_fence_wait() for everyone by default.
> > > >
> > > > - To be able to freely annotate helper functions I want to make it ok
> > > >   to call dma_fence_begin/end_signalling from soft/hardirq context.
> > > >   First attempt was using the hardirq locking context for the write
> > > >   side in lockdep, but this forces all normal spinlocks nested within
> > > >   dma_fence_begin/end_signalling to be spinlocks. That bollocks.
> > > >
> > > >   The approach now is to simple check in_atomic(), and for these cases
> > > >   entirely rely on the might_sleep() check in dma_fence_wait(). That
> > > >   will catch any wrong nesting against spinlocks from soft/hardirq
> > > >   contexts.
> > > >
> > > > The idea here is that every code path that's critical for eventually
> > > > signalling a dma_fence should be annotated with
> > > > dma_fence_begin/end_signalling. The annotation ideally starts right
> > > > after a dma_fence is published (added to a dma_resv, exposed as a
> > > > sync_file fd, attached to a drm_syncobj fd, or anything else that
> > > > makes the dma_fence visible to other kernel threads), up to and
> > > > including the dma_fence_wait(). Examples are irq handlers, the
> > > > scheduler rt threads, the tail of execbuf (after the corresponding
> > > > fences are visible), any workers that end up signalling dma_fences and
> > > > really anything else. Not annotated should be code paths that only
> > > > complete fences opportunistically as the gpu progresses, like e.g.
> > > > shrinker/eviction code.
> > > >
> > > > The main class of deadlocks this is supposed to catch are:
> > > >
> > > > Thread A:
> > > >
> > > >         mutex_lock(A);
> > > >         mutex_unlock(A);
> > > >
> > > >         dma_fence_signal();
> > > >
> > > > Thread B:
> > > >
> > > >         mutex_lock(A);
> > > >         dma_fence_wait();
> > > >         mutex_unlock(A);
> > > >
> > > > Thread B is blocked on A signalling the fence, but A never gets around
> > > > to that because it cannot acquire the lock A.
> > > >
> > > > Note that dma_fence_wait() is allowed to be nested within
> > > > dma_fence_begin/end_signalling sections. To allow this to happen the
> > > > read lock needs to be upgraded to a write lock, which means that any
> > > > other lock is acquired between the dma_fence_begin_signalling() call and
> > > > the call to dma_fence_wait(), and still held, this will result in an
> > > > immediate lockdep complaint. The only other option would be to not
> > > > annotate such calls, defeating the point. Therefore these annotations
> > > > cannot be sprinkled over the code entirely mindless to avoid false
> > > > positives.
> > > >
> > > > v2: handle soft/hardirq ctx better against write side and dont forget
> > > > EXPORT_SYMBOL, drivers can't use this otherwise.
> > > >
> > > > Cc: linux-media@vger.kernel.org
> > > > Cc: linaro-mm-sig@lists.linaro.org
> > > > Cc: linux-rdma@vger.kernel.org
> > > > Cc: amd-gfx@lists.freedesktop.org
> > > > Cc: intel-gfx@lists.freedesktop.org
> > > > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > > > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > > > Cc: Christian König <christian.koenig@amd.com>
> > > > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > > > ---
> > > >  drivers/dma-buf/dma-fence.c | 53 +++++++++++++++++++++++++++++++++++++
> > > >  include/linux/dma-fence.h   | 12 +++++++++
> > > >  2 files changed, 65 insertions(+)
> > > >
> > > > diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> > > > index 6802125349fb..d5c0fd2efc70 100644
> > > > --- a/drivers/dma-buf/dma-fence.c
> > > > +++ b/drivers/dma-buf/dma-fence.c
> > > > @@ -110,6 +110,52 @@ u64 dma_fence_context_alloc(unsigned num)
> > > >  }
> > > >  EXPORT_SYMBOL(dma_fence_context_alloc);
> > > >
> > > > +#ifdef CONFIG_LOCKDEP
> > > > +struct lockdep_map     dma_fence_lockdep_map = {
> > > > +       .name = "dma_fence_map"
> > > > +};
> > >
> > > Not another false global sharing lockmap.
> >
> > It's a global contract, it needs a global lockdep map. And yes a big
> > reason for the motivation here is that i915-gem has a tremendous urge to
> > just redefine all these global locks to fit to some local interpretation
> > of what's going on.
>
> No, you can build the global contract out of the actual contracts
> between fence drivers. If you introduce a struct lockdep_map *map into
> the fence_ops (so the fence_ops can remain const), you gain correctness
> at the cost of having to run through all possible interactions once.
> You can also then do if ops->lockmap ?: &global_fence_lockmap for
> piecemeal conversion of drivers that do not already use lockmaps for
> contract enforcement of their fence waits.

I'm not quite sure whether you're actually proposing to have locking
contracts per drivers, since that seems rather out of ... I dunno. But
if that's what you want, that just doesn't make any sense at all:

- Locking is rather core to kernel programming, aside from a few other
things like hard/softirq/preempt/... disabled sections and how
recursion works for these, or where and what you're allowed to
allocate memory. Lockdep, might_sleep and a bunch of other such debug
checks help us enforce that. If you instead go with every driver does
what they please yolo, then you don't have an abstraction, all you
have is smashing a rose and rose and Rose into one thing because they
have the same 4 letter name. It's just an interface that can be used
only when understanding every single implementation in detail - really
not something that's an abstraction. Yes I've seen some of these
dubious abstractions in i915, merged fairly recently, that doesn't
make them a good idea.

- You need to test the full NxN matrix (yes you need to test the
driver against itself in this world, since testing against something
fake like vgem doesn't cut it). That's nuts. Strike that, that's
impossible.

- Review is impossible, because the documentation can be summed up as
"yolo". Without clear rules all review can do is check every code
against every other piece of code, on every change. That's impossible,
because we humans are mere mortals, and we're left with push&pray
engineering, which really isn't.

The other issue with this approach is that it's full on platform
problem in extremis. Instead of extending the shared abstraction or
adding new useful functionality, i915-gem has resorted to reinpreting
rules to fix local problems. That leads to stuff like roughly

if (mutex_lock_timeout(HZ*10) == -ETIME) {
    /* I guess we deadlocked, try to bail out */
}

except it's for fences. That's neither solid engineering - we don't
generally let the kernel deadlock on itself to test whether maybe it
was a deadlock or not, nor is this solid upstreaming in a open source
project - we fix the problems where they are, not work around them
just in our own driver.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 08/17] drm/scheduler: use dma-fence annotations in main thread

[Daniel Vetter]

On Tue, May 12, 2020 at 11:00 AM Daniel Vetter <daniel.vetter@ffwll.ch> wrote:
>
> If the scheduler rt thread gets stuck on a mutex that we're holding
> while waiting for gpu workloads to complete, we have a problem.
>
> Add dma-fence annotations so that lockdep can check this for us.
>
> I've tried to quite carefully review this, and I think it's at the
> right spot. But obviosly no expert on drm scheduler.
>
> Cc: linux-media@vger.kernel.org
> Cc: linaro-mm-sig@lists.linaro.org
> Cc: linux-rdma@vger.kernel.org
> Cc: amd-gfx@lists.freedesktop.org
> Cc: intel-gfx@lists.freedesktop.org
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Christian König <christian.koenig@amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

Adding a bunch more people from drivers using the drm/scheduler (so
that's maintainers for etnaviv, lima, panfrost, and v3d on top of
amdgpu folks arlready on cc). Any takes or testing on this and well
the entire series very much appreciated, there's also another patch to
anotate the tdr work in this series. Plus ofc the prep work.

Thanks, Daniel

> ---
>  drivers/gpu/drm/scheduler/sched_main.c | 6 ++++++
>  1 file changed, 6 insertions(+)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index 2f319102ae9f..06a736e506ad 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -763,9 +763,12 @@ static int drm_sched_main(void *param)
>         struct sched_param sparam = {.sched_priority = 1};
>         struct drm_gpu_scheduler *sched = (struct drm_gpu_scheduler *)param;
>         int r;
> +       bool fence_cookie;
>
>         sched_setscheduler(current, SCHED_FIFO, &sparam);
>
> +       fence_cookie = dma_fence_begin_signalling();
> +
>         while (!kthread_should_stop()) {
>                 struct drm_sched_entity *entity = NULL;
>                 struct drm_sched_fence *s_fence;
> @@ -823,6 +826,9 @@ static int drm_sched_main(void *param)
>
>                 wake_up(&sched->job_scheduled);
>         }
> +
> +       dma_fence_end_signalling(fence_cookie);
> +
>         return 0;
>  }
>
> --
> 2.26.2
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 02/17] dma-fence: basic lockdep annotations

[Daniel Vetter]

On Tue, May 12, 2020 at 11:04 AM Chris Wilson <chris@chris-wilson.co.uk> wrote:
>
> Quoting Daniel Vetter (2020-05-12 09:59:29)
> > Design is similar to the lockdep annotations for workers, but with
> > some twists:
> >
> > - We use a read-lock for the execution/worker/completion side, so that
> >   this explicit annotation can be more liberally sprinkled around.
> >   With read locks lockdep isn't going to complain if the read-side
> >   isn't nested the same way under all circumstances, so ABBA deadlocks
> >   are ok. Which they are, since this is an annotation only.
> >
> > - We're using non-recursive lockdep read lock mode, since in recursive
> >   read lock mode lockdep does not catch read side hazards. And we
> >   _very_ much want read side hazards to be caught. For full details of
> >   this limitation see
> >
> >   commit e91498589746065e3ae95d9a00b068e525eec34f
> >   Author: Peter Zijlstra <peterz@infradead.org>
> >   Date:   Wed Aug 23 13:13:11 2017 +0200
> >
> >       locking/lockdep/selftests: Add mixed read-write ABBA tests
> >
> > - To allow nesting of the read-side explicit annotations we explicitly
> >   keep track of the nesting. lock_is_held() allows us to do that.
> >
> > - The wait-side annotation is a write lock, and entirely done within
> >   dma_fence_wait() for everyone by default.
> >
> > - To be able to freely annotate helper functions I want to make it ok
> >   to call dma_fence_begin/end_signalling from soft/hardirq context.
> >   First attempt was using the hardirq locking context for the write
> >   side in lockdep, but this forces all normal spinlocks nested within
> >   dma_fence_begin/end_signalling to be spinlocks. That bollocks.
> >
> >   The approach now is to simple check in_atomic(), and for these cases
> >   entirely rely on the might_sleep() check in dma_fence_wait(). That
> >   will catch any wrong nesting against spinlocks from soft/hardirq
> >   contexts.
> >
> > The idea here is that every code path that's critical for eventually
> > signalling a dma_fence should be annotated with
> > dma_fence_begin/end_signalling. The annotation ideally starts right
> > after a dma_fence is published (added to a dma_resv, exposed as a
> > sync_file fd, attached to a drm_syncobj fd, or anything else that
> > makes the dma_fence visible to other kernel threads), up to and
> > including the dma_fence_wait(). Examples are irq handlers, the
> > scheduler rt threads, the tail of execbuf (after the corresponding
> > fences are visible), any workers that end up signalling dma_fences and
> > really anything else. Not annotated should be code paths that only
> > complete fences opportunistically as the gpu progresses, like e.g.
> > shrinker/eviction code.
> >
> > The main class of deadlocks this is supposed to catch are:
> >
> > Thread A:
> >
> >         mutex_lock(A);
> >         mutex_unlock(A);
> >
> >         dma_fence_signal();
> >
> > Thread B:
> >
> >         mutex_lock(A);
> >         dma_fence_wait();
> >         mutex_unlock(A);
> >
> > Thread B is blocked on A signalling the fence, but A never gets around
> > to that because it cannot acquire the lock A.
> >
> > Note that dma_fence_wait() is allowed to be nested within
> > dma_fence_begin/end_signalling sections. To allow this to happen the
> > read lock needs to be upgraded to a write lock, which means that any
> > other lock is acquired between the dma_fence_begin_signalling() call and
> > the call to dma_fence_wait(), and still held, this will result in an
> > immediate lockdep complaint. The only other option would be to not
> > annotate such calls, defeating the point. Therefore these annotations
> > cannot be sprinkled over the code entirely mindless to avoid false
> > positives.
> >
> > v2: handle soft/hardirq ctx better against write side and dont forget
> > EXPORT_SYMBOL, drivers can't use this otherwise.
> >
> > Cc: linux-media@vger.kernel.org
> > Cc: linaro-mm-sig@lists.linaro.org
> > Cc: linux-rdma@vger.kernel.org
> > Cc: amd-gfx@lists.freedesktop.org
> > Cc: intel-gfx@lists.freedesktop.org
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Christian König <christian.koenig@amd.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > ---
> >  drivers/dma-buf/dma-fence.c | 53 +++++++++++++++++++++++++++++++++++++
> >  include/linux/dma-fence.h   | 12 +++++++++
> >  2 files changed, 65 insertions(+)
> >
> > diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> > index 6802125349fb..d5c0fd2efc70 100644
> > --- a/drivers/dma-buf/dma-fence.c
> > +++ b/drivers/dma-buf/dma-fence.c
> > @@ -110,6 +110,52 @@ u64 dma_fence_context_alloc(unsigned num)
> >  }
> >  EXPORT_SYMBOL(dma_fence_context_alloc);
> >
> > +#ifdef CONFIG_LOCKDEP
> > +struct lockdep_map     dma_fence_lockdep_map = {
> > +       .name = "dma_fence_map"
> > +};
>
> Not another false global sharing lockmap.

So in some meetings you also mentioned nesting is going to be a
problem here. I see about three different kinds of nesting here, but
none should be a fundamental problem:

- nesting of fence drivers, specifically the syncobj timeline fences
but there's others around dma_fence->lock. This series is about
blocking deadlocks, it doesn't care about irqsave spinlocks at all. So
all the nesting going on there is entirely unchanged. Validation
against atomic section relies on the might_sleep annotation in the
first patch.

- nesting of callers, for better code composability. The annotations
are recursive, I've tested it with amdgpu, works.

- nesting of timelines, where e.g. you have some scheduler completion
events that drive the scheduler logic, which eventually will also
result in userspace visible fences on some context getting completed.
Works for amdgpu, that's why I annotated the scheduler. Also, not a
problem for two reasons:

1. uapi relevant fences are the relevant fences for the cross-driver
contract. Building something outside of them few fewer constraints
doesn't make sense, that would just mean we make the dma_fence
cross-driver contract less strict (but then for everyone, not just for
one driver, cause that asymmetric doesn't really work)

2. fences entirely hidden in drivers, which driver something
underneath the uapi visible fences (like scheduler or whatever). Those
can be more constraint, but as long as they're driving the public
fences, can't be less constrained. So cross-driver annotations don't
give you any limitations, you still can do your own driver-internal
annotations to track this more strict constraints.

So really not seeing the fence nesting issue here, either it's a
totally different one, or I'm misunderstood something.

I guess the other issue is that there's a ton of code that's broken
all around in various drivers, but that's why the RFC part. I
specifically highlighted that the priming patch needs some serious
discussion, but "nope I don't want a cross driver contract" really
isn't that.

Cheers, Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 02/17] dma-fence: basic lockdep annotations

[Maarten Lankhorst]

Op 12-05-2020 om 10:59 schreef Daniel Vetter:
> Design is similar to the lockdep annotations for workers, but with
> some twists:
>
> - We use a read-lock for the execution/worker/completion side, so that
>   this explicit annotation can be more liberally sprinkled around.
>   With read locks lockdep isn't going to complain if the read-side
>   isn't nested the same way under all circumstances, so ABBA deadlocks
>   are ok. Which they are, since this is an annotation only.
>
> - We're using non-recursive lockdep read lock mode, since in recursive
>   read lock mode lockdep does not catch read side hazards. And we
>   _very_ much want read side hazards to be caught. For full details of
>   this limitation see
>
>   commit e91498589746065e3ae95d9a00b068e525eec34f
>   Author: Peter Zijlstra <peterz@infradead.org>
>   Date:   Wed Aug 23 13:13:11 2017 +0200
>
>       locking/lockdep/selftests: Add mixed read-write ABBA tests
>
> - To allow nesting of the read-side explicit annotations we explicitly
>   keep track of the nesting. lock_is_held() allows us to do that.
>
> - The wait-side annotation is a write lock, and entirely done within
>   dma_fence_wait() for everyone by default.
>
> - To be able to freely annotate helper functions I want to make it ok
>   to call dma_fence_begin/end_signalling from soft/hardirq context.
>   First attempt was using the hardirq locking context for the write
>   side in lockdep, but this forces all normal spinlocks nested within
>   dma_fence_begin/end_signalling to be spinlocks. That bollocks.
>
>   The approach now is to simple check in_atomic(), and for these cases
>   entirely rely on the might_sleep() check in dma_fence_wait(). That
>   will catch any wrong nesting against spinlocks from soft/hardirq
>   contexts.
>
> The idea here is that every code path that's critical for eventually
> signalling a dma_fence should be annotated with
> dma_fence_begin/end_signalling. The annotation ideally starts right
> after a dma_fence is published (added to a dma_resv, exposed as a
> sync_file fd, attached to a drm_syncobj fd, or anything else that
> makes the dma_fence visible to other kernel threads), up to and
> including the dma_fence_wait(). Examples are irq handlers, the
> scheduler rt threads, the tail of execbuf (after the corresponding
> fences are visible), any workers that end up signalling dma_fences and
> really anything else. Not annotated should be code paths that only
> complete fences opportunistically as the gpu progresses, like e.g.
> shrinker/eviction code.
>
> The main class of deadlocks this is supposed to catch are:
>
> Thread A:
>
> 	mutex_lock(A);
> 	mutex_unlock(A);
>
> 	dma_fence_signal();
>
> Thread B:
>
> 	mutex_lock(A);
> 	dma_fence_wait();
> 	mutex_unlock(A);
>
> Thread B is blocked on A signalling the fence, but A never gets around
> to that because it cannot acquire the lock A.
>
> Note that dma_fence_wait() is allowed to be nested within
> dma_fence_begin/end_signalling sections. To allow this to happen the
> read lock needs to be upgraded to a write lock, which means that any
> other lock is acquired between the dma_fence_begin_signalling() call and
> the call to dma_fence_wait(), and still held, this will result in an
> immediate lockdep complaint. The only other option would be to not
> annotate such calls, defeating the point. Therefore these annotations
> cannot be sprinkled over the code entirely mindless to avoid false
> positives.
>
> v2: handle soft/hardirq ctx better against write side and dont forget
> EXPORT_SYMBOL, drivers can't use this otherwise.
>
> Cc: linux-media@vger.kernel.org
> Cc: linaro-mm-sig@lists.linaro.org
> Cc: linux-rdma@vger.kernel.org
> Cc: amd-gfx@lists.freedesktop.org
> Cc: intel-gfx@lists.freedesktop.org
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Christian König <christian.koenig@amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---

This is something we definitely need, all drivers need to follow the same rules, in order to put some light in the darkness. :)

Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>

>  drivers/dma-buf/dma-fence.c | 53 +++++++++++++++++++++++++++++++++++++
>  include/linux/dma-fence.h   | 12 +++++++++
>  2 files changed, 65 insertions(+)
>
> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> index 6802125349fb..d5c0fd2efc70 100644
> --- a/drivers/dma-buf/dma-fence.c
> +++ b/drivers/dma-buf/dma-fence.c
> @@ -110,6 +110,52 @@ u64 dma_fence_context_alloc(unsigned num)
>  }
>  EXPORT_SYMBOL(dma_fence_context_alloc);
>  
> +#ifdef CONFIG_LOCKDEP
> +struct lockdep_map	dma_fence_lockdep_map = {
> +	.name = "dma_fence_map"
> +};
> +
> +bool dma_fence_begin_signalling(void)
> +{
> +	/* explicitly nesting ... */
> +	if (lock_is_held_type(&dma_fence_lockdep_map, 1))
> +		return true;
> +
> +	/* rely on might_sleep check for soft/hardirq locks */
> +	if (in_atomic())
> +		return true;
> +
> +	/* ... and non-recursive readlock */
> +	lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _RET_IP_);
> +
> +	return false;
> +}
> +EXPORT_SYMBOL(dma_fence_begin_signalling);
> +
> +void dma_fence_end_signalling(bool cookie)
> +{
> +	if (cookie)
> +		return;
> +
> +	lock_release(&dma_fence_lockdep_map, _RET_IP_);
> +}
> +EXPORT_SYMBOL(dma_fence_end_signalling);
> +
> +void __dma_fence_might_wait(void)
> +{
> +	bool tmp;
> +
> +	tmp = lock_is_held_type(&dma_fence_lockdep_map, 1);
> +	if (tmp)
> +		lock_release(&dma_fence_lockdep_map, _THIS_IP_);
> +	lock_map_acquire(&dma_fence_lockdep_map);
> +	lock_map_release(&dma_fence_lockdep_map);
> +	if (tmp)
> +		lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _THIS_IP_);
> +}
> +#endif
> +
> +
>  /**
>   * dma_fence_signal_locked - signal completion of a fence
>   * @fence: the fence to signal
> @@ -170,14 +216,19 @@ int dma_fence_signal(struct dma_fence *fence)
>  {
>  	unsigned long flags;
>  	int ret;
> +	bool tmp;
>  
>  	if (!fence)
>  		return -EINVAL;
>  
> +	tmp = dma_fence_begin_signalling();
> +
>  	spin_lock_irqsave(fence->lock, flags);
>  	ret = dma_fence_signal_locked(fence);
>  	spin_unlock_irqrestore(fence->lock, flags);
>  
> +	dma_fence_end_signalling(tmp);
> +
>  	return ret;
>  }
>  EXPORT_SYMBOL(dma_fence_signal);
> @@ -211,6 +262,8 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
>  	if (timeout > 0)
>  		might_sleep();
>  
> +	__dma_fence_might_wait();
> +
>  	trace_dma_fence_wait_start(fence);
>  	if (fence->ops->wait)
>  		ret = fence->ops->wait(fence, intr, timeout);
> diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> index 3347c54f3a87..3f288f7db2ef 100644
> --- a/include/linux/dma-fence.h
> +++ b/include/linux/dma-fence.h
> @@ -357,6 +357,18 @@ dma_fence_get_rcu_safe(struct dma_fence __rcu **fencep)
>  	} while (1);
>  }
>  
> +#ifdef CONFIG_LOCKDEP
> +bool dma_fence_begin_signalling(void);
> +void dma_fence_end_signalling(bool cookie);
> +#else
> +static inline bool dma_fence_begin_signalling(void)
> +{
> +	return true;
> +}
> +static inline void dma_fence_end_signalling(bool cookie) {}
> +static inline void __dma_fence_might_wait(void) {}
> +#endif
> +
>  int dma_fence_signal(struct dma_fence *fence);
>  int dma_fence_signal_locked(struct dma_fence *fence);
>  signed long dma_fence_default_wait(struct dma_fence *fence,

Re: [RFC 02/17] dma-fence: basic lockdep annotations

[Thomas Hellström (Intel)]

On 2020-05-12 10:59, Daniel Vetter wrote:
> Design is similar to the lockdep annotations for workers, but with
> some twists:
>
> - We use a read-lock for the execution/worker/completion side, so that
>    this explicit annotation can be more liberally sprinkled around.
>    With read locks lockdep isn't going to complain if the read-side
>    isn't nested the same way under all circumstances, so ABBA deadlocks
>    are ok. Which they are, since this is an annotation only.
>
> - We're using non-recursive lockdep read lock mode, since in recursive
>    read lock mode lockdep does not catch read side hazards. And we
>    _very_ much want read side hazards to be caught. For full details of
>    this limitation see
>
>    commit e91498589746065e3ae95d9a00b068e525eec34f
>    Author: Peter Zijlstra <peterz@infradead.org>
>    Date:   Wed Aug 23 13:13:11 2017 +0200
>
>        locking/lockdep/selftests: Add mixed read-write ABBA tests
>
> - To allow nesting of the read-side explicit annotations we explicitly
>    keep track of the nesting. lock_is_held() allows us to do that.
>
> - The wait-side annotation is a write lock, and entirely done within
>    dma_fence_wait() for everyone by default.
>
> - To be able to freely annotate helper functions I want to make it ok
>    to call dma_fence_begin/end_signalling from soft/hardirq context.
>    First attempt was using the hardirq locking context for the write
>    side in lockdep, but this forces all normal spinlocks nested within
>    dma_fence_begin/end_signalling to be spinlocks. That bollocks.
>
>    The approach now is to simple check in_atomic(), and for these cases
>    entirely rely on the might_sleep() check in dma_fence_wait(). That
>    will catch any wrong nesting against spinlocks from soft/hardirq
>    contexts.
>
> The idea here is that every code path that's critical for eventually
> signalling a dma_fence should be annotated with
> dma_fence_begin/end_signalling. The annotation ideally starts right
> after a dma_fence is published (added to a dma_resv, exposed as a
> sync_file fd, attached to a drm_syncobj fd, or anything else that
> makes the dma_fence visible to other kernel threads), up to and
> including the dma_fence_wait(). Examples are irq handlers, the
> scheduler rt threads, the tail of execbuf (after the corresponding
> fences are visible), any workers that end up signalling dma_fences and
> really anything else. Not annotated should be code paths that only
> complete fences opportunistically as the gpu progresses, like e.g.
> shrinker/eviction code.
>
> The main class of deadlocks this is supposed to catch are:
>
> Thread A:
>
> 	mutex_lock(A);
> 	mutex_unlock(A);
>
> 	dma_fence_signal();
>
> Thread B:
>
> 	mutex_lock(A);
> 	dma_fence_wait();
> 	mutex_unlock(A);
>
> Thread B is blocked on A signalling the fence, but A never gets around
> to that because it cannot acquire the lock A.
>
> Note that dma_fence_wait() is allowed to be nested within
> dma_fence_begin/end_signalling sections. To allow this to happen the
> read lock needs to be upgraded to a write lock, which means that any
> other lock is acquired between the dma_fence_begin_signalling() call and
> the call to dma_fence_wait(), and still held, this will result in an
> immediate lockdep complaint. The only other option would be to not
> annotate such calls, defeating the point. Therefore these annotations
> cannot be sprinkled over the code entirely mindless to avoid false
> positives.
>
> v2: handle soft/hardirq ctx better against write side and dont forget
> EXPORT_SYMBOL, drivers can't use this otherwise.
>
> Cc: linux-media@vger.kernel.org
> Cc: linaro-mm-sig@lists.linaro.org
> Cc: linux-rdma@vger.kernel.org
> Cc: amd-gfx@lists.freedesktop.org
> Cc: intel-gfx@lists.freedesktop.org
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Christian König <christian.koenig@amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>

LGTM. Perhaps some in-code documentation on how to use the new functions 
are called.

Otherwise for patch 2 and 3,

Reviewed-by: Thomas Hellstrom <thomas.hellstrom@intel.com>

Re: [RFC 02/17] dma-fence: basic lockdep annotations

[Daniel Vetter]

On Thu, May 28, 2020 at 3:37 PM Thomas Hellström (Intel)
<thomas_os@shipmail.org> wrote:
>
> On 2020-05-12 10:59, Daniel Vetter wrote:
> > Design is similar to the lockdep annotations for workers, but with
> > some twists:
> >
> > - We use a read-lock for the execution/worker/completion side, so that
> >    this explicit annotation can be more liberally sprinkled around.
> >    With read locks lockdep isn't going to complain if the read-side
> >    isn't nested the same way under all circumstances, so ABBA deadlocks
> >    are ok. Which they are, since this is an annotation only.
> >
> > - We're using non-recursive lockdep read lock mode, since in recursive
> >    read lock mode lockdep does not catch read side hazards. And we
> >    _very_ much want read side hazards to be caught. For full details of
> >    this limitation see
> >
> >    commit e91498589746065e3ae95d9a00b068e525eec34f
> >    Author: Peter Zijlstra <peterz@infradead.org>
> >    Date:   Wed Aug 23 13:13:11 2017 +0200
> >
> >        locking/lockdep/selftests: Add mixed read-write ABBA tests
> >
> > - To allow nesting of the read-side explicit annotations we explicitly
> >    keep track of the nesting. lock_is_held() allows us to do that.
> >
> > - The wait-side annotation is a write lock, and entirely done within
> >    dma_fence_wait() for everyone by default.
> >
> > - To be able to freely annotate helper functions I want to make it ok
> >    to call dma_fence_begin/end_signalling from soft/hardirq context.
> >    First attempt was using the hardirq locking context for the write
> >    side in lockdep, but this forces all normal spinlocks nested within
> >    dma_fence_begin/end_signalling to be spinlocks. That bollocks.
> >
> >    The approach now is to simple check in_atomic(), and for these cases
> >    entirely rely on the might_sleep() check in dma_fence_wait(). That
> >    will catch any wrong nesting against spinlocks from soft/hardirq
> >    contexts.
> >
> > The idea here is that every code path that's critical for eventually
> > signalling a dma_fence should be annotated with
> > dma_fence_begin/end_signalling. The annotation ideally starts right
> > after a dma_fence is published (added to a dma_resv, exposed as a
> > sync_file fd, attached to a drm_syncobj fd, or anything else that
> > makes the dma_fence visible to other kernel threads), up to and
> > including the dma_fence_wait(). Examples are irq handlers, the
> > scheduler rt threads, the tail of execbuf (after the corresponding
> > fences are visible), any workers that end up signalling dma_fences and
> > really anything else. Not annotated should be code paths that only
> > complete fences opportunistically as the gpu progresses, like e.g.
> > shrinker/eviction code.
> >
> > The main class of deadlocks this is supposed to catch are:
> >
> > Thread A:
> >
> >       mutex_lock(A);
> >       mutex_unlock(A);
> >
> >       dma_fence_signal();
> >
> > Thread B:
> >
> >       mutex_lock(A);
> >       dma_fence_wait();
> >       mutex_unlock(A);
> >
> > Thread B is blocked on A signalling the fence, but A never gets around
> > to that because it cannot acquire the lock A.
> >
> > Note that dma_fence_wait() is allowed to be nested within
> > dma_fence_begin/end_signalling sections. To allow this to happen the
> > read lock needs to be upgraded to a write lock, which means that any
> > other lock is acquired between the dma_fence_begin_signalling() call and
> > the call to dma_fence_wait(), and still held, this will result in an
> > immediate lockdep complaint. The only other option would be to not
> > annotate such calls, defeating the point. Therefore these annotations
> > cannot be sprinkled over the code entirely mindless to avoid false
> > positives.
> >
> > v2: handle soft/hardirq ctx better against write side and dont forget
> > EXPORT_SYMBOL, drivers can't use this otherwise.
> >
> > Cc: linux-media@vger.kernel.org
> > Cc: linaro-mm-sig@lists.linaro.org
> > Cc: linux-rdma@vger.kernel.org
> > Cc: amd-gfx@lists.freedesktop.org
> > Cc: intel-gfx@lists.freedesktop.org
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Christian König <christian.koenig@amd.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
>
> LGTM. Perhaps some in-code documentation on how to use the new functions
> are called.

See cover letter, that's going to be done for next round. For this one
here I just wanted to showcase a bit how it's used in a few different
places, mostly selected to get as much feedback from across different
drivers. Hence e.g. annotating drm/scheduler.

> Otherwise for patch 2 and 3,
>
> Reviewed-by: Thomas Hellstrom <thomas.hellstrom@intel.com>

I think I'll just cc you for the next round with docs, so you can make
sure it looks ok :-)
-Daniel
-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 02/17] dma-fence: basic lockdep annotations

[Luben Tuikov]

On 2020-05-12 4:59 a.m., Daniel Vetter wrote:
> Design is similar to the lockdep annotations for workers, but with
> some twists:
> 
> - We use a read-lock for the execution/worker/completion side, so that
>   this explicit annotation can be more liberally sprinkled around.
>   With read locks lockdep isn't going to complain if the read-side
>   isn't nested the same way under all circumstances, so ABBA deadlocks
>   are ok. Which they are, since this is an annotation only.
> 
> - We're using non-recursive lockdep read lock mode, since in recursive
>   read lock mode lockdep does not catch read side hazards. And we
>   _very_ much want read side hazards to be caught. For full details of
>   this limitation see
> 
>   commit e91498589746065e3ae95d9a00b068e525eec34f
>   Author: Peter Zijlstra <peterz@infradead.org>
>   Date:   Wed Aug 23 13:13:11 2017 +0200
> 
>       locking/lockdep/selftests: Add mixed read-write ABBA tests
> 
> - To allow nesting of the read-side explicit annotations we explicitly
>   keep track of the nesting. lock_is_held() allows us to do that.
> 
> - The wait-side annotation is a write lock, and entirely done within
>   dma_fence_wait() for everyone by default.
> 
> - To be able to freely annotate helper functions I want to make it ok
>   to call dma_fence_begin/end_signalling from soft/hardirq context.
>   First attempt was using the hardirq locking context for the write
>   side in lockdep, but this forces all normal spinlocks nested within
>   dma_fence_begin/end_signalling to be spinlocks. That bollocks.
> 
>   The approach now is to simple check in_atomic(), and for these cases
>   entirely rely on the might_sleep() check in dma_fence_wait(). That
>   will catch any wrong nesting against spinlocks from soft/hardirq
>   contexts.
> 
> The idea here is that every code path that's critical for eventually
> signalling a dma_fence should be annotated with
> dma_fence_begin/end_signalling. The annotation ideally starts right
> after a dma_fence is published (added to a dma_resv, exposed as a
> sync_file fd, attached to a drm_syncobj fd, or anything else that
> makes the dma_fence visible to other kernel threads), up to and
> including the dma_fence_wait(). Examples are irq handlers, the
> scheduler rt threads, the tail of execbuf (after the corresponding
> fences are visible), any workers that end up signalling dma_fences and
> really anything else. Not annotated should be code paths that only
> complete fences opportunistically as the gpu progresses, like e.g.
> shrinker/eviction code.
> 
> The main class of deadlocks this is supposed to catch are:
> 
> Thread A:
> 
> 	mutex_lock(A);
> 	mutex_unlock(A);
> 
> 	dma_fence_signal();
> 
> Thread B:
> 
> 	mutex_lock(A);
> 	dma_fence_wait();
> 	mutex_unlock(A);
> 
> Thread B is blocked on A signalling the fence, but A never gets around
> to that because it cannot acquire the lock A.
> 
> Note that dma_fence_wait() is allowed to be nested within
> dma_fence_begin/end_signalling sections. To allow this to happen the
> read lock needs to be upgraded to a write lock, which means that any
> other lock is acquired between the dma_fence_begin_signalling() call and
> the call to dma_fence_wait(), and still held, this will result in an
> immediate lockdep complaint. The only other option would be to not
> annotate such calls, defeating the point. Therefore these annotations
> cannot be sprinkled over the code entirely mindless to avoid false
> positives.
> 
> v2: handle soft/hardirq ctx better against write side and dont forget
> EXPORT_SYMBOL, drivers can't use this otherwise.
> 
> Cc: linux-media@vger.kernel.org
> Cc: linaro-mm-sig@lists.linaro.org
> Cc: linux-rdma@vger.kernel.org
> Cc: amd-gfx@lists.freedesktop.org
> Cc: intel-gfx@lists.freedesktop.org
> Cc: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> Cc: Christian König <christian.koenig@amd.com>
> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> ---
>  drivers/dma-buf/dma-fence.c | 53 +++++++++++++++++++++++++++++++++++++
>  include/linux/dma-fence.h   | 12 +++++++++
>  2 files changed, 65 insertions(+)
> 
> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> index 6802125349fb..d5c0fd2efc70 100644
> --- a/drivers/dma-buf/dma-fence.c
> +++ b/drivers/dma-buf/dma-fence.c
> @@ -110,6 +110,52 @@ u64 dma_fence_context_alloc(unsigned num)
>  }
>  EXPORT_SYMBOL(dma_fence_context_alloc);
>  
> +#ifdef CONFIG_LOCKDEP
> +struct lockdep_map	dma_fence_lockdep_map = {
> +	.name = "dma_fence_map"
> +};
> +
> +bool dma_fence_begin_signalling(void)
> +{
> +	/* explicitly nesting ... */
> +	if (lock_is_held_type(&dma_fence_lockdep_map, 1))
> +		return true;
> +
> +	/* rely on might_sleep check for soft/hardirq locks */
> +	if (in_atomic())
> +		return true;
> +
> +	/* ... and non-recursive readlock */
> +	lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _RET_IP_);
> +
> +	return false;
> +}
> +EXPORT_SYMBOL(dma_fence_begin_signalling);

Hi Daniel,

This is great work and could help a lot.

If you invert the result of dma_fence_begin_signalling()
then it would naturally mean "locked", i.e. whether we need to
later release "dma_fence_lockedep_map". Then,
in dma_fence_end_signalling(), you can call the "cookie"
argument "locked" and simply do:

void dma_fence_end_signalling(bool locked)
{
	if (locked)
		lock_release(&dma_fence_lockdep_map, _RET_IP_);
}
EXPORT_SYMBOL(dma_fence_end_signalling);

It'll be more natural to understand as well.

Regards,
Luben

> +
> +void dma_fence_end_signalling(bool cookie)
> +{
> +	if (cookie)
> +		return;
> +
> +	lock_release(&dma_fence_lockdep_map, _RET_IP_);
> +}
> +EXPORT_SYMBOL(dma_fence_end_signalling);
> +
> +void __dma_fence_might_wait(void)
> +{
> +	bool tmp;
> +
> +	tmp = lock_is_held_type(&dma_fence_lockdep_map, 1);
> +	if (tmp)
> +		lock_release(&dma_fence_lockdep_map, _THIS_IP_);
> +	lock_map_acquire(&dma_fence_lockdep_map);
> +	lock_map_release(&dma_fence_lockdep_map);
> +	if (tmp)
> +		lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _THIS_IP_);
> +}
> +#endif
> +
> +
>  /**
>   * dma_fence_signal_locked - signal completion of a fence
>   * @fence: the fence to signal
> @@ -170,14 +216,19 @@ int dma_fence_signal(struct dma_fence *fence)
>  {
>  	unsigned long flags;
>  	int ret;
> +	bool tmp;
>  
>  	if (!fence)
>  		return -EINVAL;
>  
> +	tmp = dma_fence_begin_signalling();
> +
>  	spin_lock_irqsave(fence->lock, flags);
>  	ret = dma_fence_signal_locked(fence);
>  	spin_unlock_irqrestore(fence->lock, flags);
>  
> +	dma_fence_end_signalling(tmp);
> +
>  	return ret;
>  }
>  EXPORT_SYMBOL(dma_fence_signal);
> @@ -211,6 +262,8 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
>  	if (timeout > 0)
>  		might_sleep();
>  
> +	__dma_fence_might_wait();
> +
>  	trace_dma_fence_wait_start(fence);
>  	if (fence->ops->wait)
>  		ret = fence->ops->wait(fence, intr, timeout);
> diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> index 3347c54f3a87..3f288f7db2ef 100644
> --- a/include/linux/dma-fence.h
> +++ b/include/linux/dma-fence.h
> @@ -357,6 +357,18 @@ dma_fence_get_rcu_safe(struct dma_fence __rcu **fencep)
>  	} while (1);
>  }
>  
> +#ifdef CONFIG_LOCKDEP
> +bool dma_fence_begin_signalling(void);
> +void dma_fence_end_signalling(bool cookie);
> +#else
> +static inline bool dma_fence_begin_signalling(void)
> +{
> +	return true;
> +}
> +static inline void dma_fence_end_signalling(bool cookie) {}
> +static inline void __dma_fence_might_wait(void) {}
> +#endif
> +
>  int dma_fence_signal(struct dma_fence *fence);
>  int dma_fence_signal_locked(struct dma_fence *fence);
>  signed long dma_fence_default_wait(struct dma_fence *fence,
> 

Re: [RFC 02/17] dma-fence: basic lockdep annotations

[Daniel Vetter]

On Thu, May 28, 2020 at 11:54 PM Luben Tuikov <luben.tuikov@amd.com> wrote:
>
> On 2020-05-12 4:59 a.m., Daniel Vetter wrote:
> > Design is similar to the lockdep annotations for workers, but with
> > some twists:
> >
> > - We use a read-lock for the execution/worker/completion side, so that
> >   this explicit annotation can be more liberally sprinkled around.
> >   With read locks lockdep isn't going to complain if the read-side
> >   isn't nested the same way under all circumstances, so ABBA deadlocks
> >   are ok. Which they are, since this is an annotation only.
> >
> > - We're using non-recursive lockdep read lock mode, since in recursive
> >   read lock mode lockdep does not catch read side hazards. And we
> >   _very_ much want read side hazards to be caught. For full details of
> >   this limitation see
> >
> >   commit e91498589746065e3ae95d9a00b068e525eec34f
> >   Author: Peter Zijlstra <peterz@infradead.org>
> >   Date:   Wed Aug 23 13:13:11 2017 +0200
> >
> >       locking/lockdep/selftests: Add mixed read-write ABBA tests
> >
> > - To allow nesting of the read-side explicit annotations we explicitly
> >   keep track of the nesting. lock_is_held() allows us to do that.
> >
> > - The wait-side annotation is a write lock, and entirely done within
> >   dma_fence_wait() for everyone by default.
> >
> > - To be able to freely annotate helper functions I want to make it ok
> >   to call dma_fence_begin/end_signalling from soft/hardirq context.
> >   First attempt was using the hardirq locking context for the write
> >   side in lockdep, but this forces all normal spinlocks nested within
> >   dma_fence_begin/end_signalling to be spinlocks. That bollocks.
> >
> >   The approach now is to simple check in_atomic(), and for these cases
> >   entirely rely on the might_sleep() check in dma_fence_wait(). That
> >   will catch any wrong nesting against spinlocks from soft/hardirq
> >   contexts.
> >
> > The idea here is that every code path that's critical for eventually
> > signalling a dma_fence should be annotated with
> > dma_fence_begin/end_signalling. The annotation ideally starts right
> > after a dma_fence is published (added to a dma_resv, exposed as a
> > sync_file fd, attached to a drm_syncobj fd, or anything else that
> > makes the dma_fence visible to other kernel threads), up to and
> > including the dma_fence_wait(). Examples are irq handlers, the
> > scheduler rt threads, the tail of execbuf (after the corresponding
> > fences are visible), any workers that end up signalling dma_fences and
> > really anything else. Not annotated should be code paths that only
> > complete fences opportunistically as the gpu progresses, like e.g.
> > shrinker/eviction code.
> >
> > The main class of deadlocks this is supposed to catch are:
> >
> > Thread A:
> >
> >       mutex_lock(A);
> >       mutex_unlock(A);
> >
> >       dma_fence_signal();
> >
> > Thread B:
> >
> >       mutex_lock(A);
> >       dma_fence_wait();
> >       mutex_unlock(A);
> >
> > Thread B is blocked on A signalling the fence, but A never gets around
> > to that because it cannot acquire the lock A.
> >
> > Note that dma_fence_wait() is allowed to be nested within
> > dma_fence_begin/end_signalling sections. To allow this to happen the
> > read lock needs to be upgraded to a write lock, which means that any
> > other lock is acquired between the dma_fence_begin_signalling() call and
> > the call to dma_fence_wait(), and still held, this will result in an
> > immediate lockdep complaint. The only other option would be to not
> > annotate such calls, defeating the point. Therefore these annotations
> > cannot be sprinkled over the code entirely mindless to avoid false
> > positives.
> >
> > v2: handle soft/hardirq ctx better against write side and dont forget
> > EXPORT_SYMBOL, drivers can't use this otherwise.
> >
> > Cc: linux-media@vger.kernel.org
> > Cc: linaro-mm-sig@lists.linaro.org
> > Cc: linux-rdma@vger.kernel.org
> > Cc: amd-gfx@lists.freedesktop.org
> > Cc: intel-gfx@lists.freedesktop.org
> > Cc: Chris Wilson <chris@chris-wilson.co.uk>
> > Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
> > Cc: Christian König <christian.koenig@amd.com>
> > Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
> > ---
> >  drivers/dma-buf/dma-fence.c | 53 +++++++++++++++++++++++++++++++++++++
> >  include/linux/dma-fence.h   | 12 +++++++++
> >  2 files changed, 65 insertions(+)
> >
> > diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
> > index 6802125349fb..d5c0fd2efc70 100644
> > --- a/drivers/dma-buf/dma-fence.c
> > +++ b/drivers/dma-buf/dma-fence.c
> > @@ -110,6 +110,52 @@ u64 dma_fence_context_alloc(unsigned num)
> >  }
> >  EXPORT_SYMBOL(dma_fence_context_alloc);
> >
> > +#ifdef CONFIG_LOCKDEP
> > +struct lockdep_map   dma_fence_lockdep_map = {
> > +     .name = "dma_fence_map"
> > +};
> > +
> > +bool dma_fence_begin_signalling(void)
> > +{
> > +     /* explicitly nesting ... */
> > +     if (lock_is_held_type(&dma_fence_lockdep_map, 1))
> > +             return true;
> > +
> > +     /* rely on might_sleep check for soft/hardirq locks */
> > +     if (in_atomic())
> > +             return true;
> > +
> > +     /* ... and non-recursive readlock */
> > +     lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _RET_IP_);
> > +
> > +     return false;
> > +}
> > +EXPORT_SYMBOL(dma_fence_begin_signalling);
>
> Hi Daniel,
>
> This is great work and could help a lot.
>
> If you invert the result of dma_fence_begin_signalling()
> then it would naturally mean "locked", i.e. whether we need to
> later release "dma_fence_lockedep_map". Then,
> in dma_fence_end_signalling(), you can call the "cookie"
> argument "locked" and simply do:
>
> void dma_fence_end_signalling(bool locked)
> {
>         if (locked)
>                 lock_release(&dma_fence_lockdep_map, _RET_IP_);
> }
> EXPORT_SYMBOL(dma_fence_end_signalling);
>
> It'll be more natural to understand as well.

It's intentionally called cookie so callers don't start doing funny
stuff with it. The thing is, after begin_signalling you are _always_
in the locked state. It's just that because of limitations with
lockdep we need to play a few tricks, and in some cases we do not take
the lockdep map. There's 2 cases:
- lockdep map already taken - we want recursive readlock semantics for
this, but lockdep does not correctly check recursive read locks. Hence
we only use readlock, and make sure we do not actually nest upon
ourselves with this explicit check.
- when we're in atomic sections - lockdep gets pissed at us if we take
the read lock in hard/softirq sections because of hard/softirq ctx
mismatch (lockdep thinks it's a real lock, but we don't treat it as
one). Simplest fix was to rely on the might_sleep check in patch 1
(already merged)

The commit message mentions this already a bit, but I'll try to
explain this implementation detail tersely in the kerneldoc too in the
next round.

Thanks, Daniel

>
> Regards,
> Luben
>
> > +
> > +void dma_fence_end_signalling(bool cookie)
> > +{
> > +     if (cookie)
> > +             return;
> > +
> > +     lock_release(&dma_fence_lockdep_map, _RET_IP_);
> > +}
> > +EXPORT_SYMBOL(dma_fence_end_signalling);
> > +
> > +void __dma_fence_might_wait(void)
> > +{
> > +     bool tmp;
> > +
> > +     tmp = lock_is_held_type(&dma_fence_lockdep_map, 1);
> > +     if (tmp)
> > +             lock_release(&dma_fence_lockdep_map, _THIS_IP_);
> > +     lock_map_acquire(&dma_fence_lockdep_map);
> > +     lock_map_release(&dma_fence_lockdep_map);
> > +     if (tmp)
> > +             lock_acquire(&dma_fence_lockdep_map, 0, 0, 1, 1, NULL, _THIS_IP_);
> > +}
> > +#endif
> > +
> > +
> >  /**
> >   * dma_fence_signal_locked - signal completion of a fence
> >   * @fence: the fence to signal
> > @@ -170,14 +216,19 @@ int dma_fence_signal(struct dma_fence *fence)
> >  {
> >       unsigned long flags;
> >       int ret;
> > +     bool tmp;
> >
> >       if (!fence)
> >               return -EINVAL;
> >
> > +     tmp = dma_fence_begin_signalling();
> > +
> >       spin_lock_irqsave(fence->lock, flags);
> >       ret = dma_fence_signal_locked(fence);
> >       spin_unlock_irqrestore(fence->lock, flags);
> >
> > +     dma_fence_end_signalling(tmp);
> > +
> >       return ret;
> >  }
> >  EXPORT_SYMBOL(dma_fence_signal);
> > @@ -211,6 +262,8 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
> >       if (timeout > 0)
> >               might_sleep();
> >
> > +     __dma_fence_might_wait();
> > +
> >       trace_dma_fence_wait_start(fence);
> >       if (fence->ops->wait)
> >               ret = fence->ops->wait(fence, intr, timeout);
> > diff --git a/include/linux/dma-fence.h b/include/linux/dma-fence.h
> > index 3347c54f3a87..3f288f7db2ef 100644
> > --- a/include/linux/dma-fence.h
> > +++ b/include/linux/dma-fence.h
> > @@ -357,6 +357,18 @@ dma_fence_get_rcu_safe(struct dma_fence __rcu **fencep)
> >       } while (1);
> >  }
> >
> > +#ifdef CONFIG_LOCKDEP
> > +bool dma_fence_begin_signalling(void);
> > +void dma_fence_end_signalling(bool cookie);
> > +#else
> > +static inline bool dma_fence_begin_signalling(void)
> > +{
> > +     return true;
> > +}
> > +static inline void dma_fence_end_signalling(bool cookie) {}
> > +static inline void __dma_fence_might_wait(void) {}
> > +#endif
> > +
> >  int dma_fence_signal(struct dma_fence *fence);
> >  int dma_fence_signal_locked(struct dma_fence *fence);
> >  signed long dma_fence_default_wait(struct dma_fence *fence,
> >
>


-- 
Daniel Vetter
Software Engineer, Intel Corporation
+41 (0) 79 365 57 48 - http://blog.ffwll.ch

Re: [RFC 01/17] dma-fence: add might_sleep annotation to _wait()

[Maarten Lankhorst]

Op 12-05-2020 om 11:08 schreef Christian König:
> Am 12.05.20 um 10:59 schrieb Daniel Vetter:
>> But only for non-zero timeout, to avoid false positives.
>>
>> One question here is whether the might_sleep should be unconditional,
>> or only for real timeouts. I'm not sure, so went with the more
>> defensive option. But in the interest of locking down the cross-driver
>> dma_fence rules we might want to be more aggressive.
>>
>> Cc: linux-media@vger.kernel.org
>> Cc: linaro-mm-sig@lists.linaro.org
>> Cc: linux-rdma@vger.kernel.org
>> Cc: amd-gfx@lists.freedesktop.org
>> Cc: intel-gfx@lists.freedesktop.org
>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>> Cc: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
>> Cc: Christian König <christian.koenig@amd.com>
>> Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
>> ---
>>   drivers/dma-buf/dma-fence.c | 3 +++
>>   1 file changed, 3 insertions(+)
>>
>> diff --git a/drivers/dma-buf/dma-fence.c b/drivers/dma-buf/dma-fence.c
>> index 052a41e2451c..6802125349fb 100644
>> --- a/drivers/dma-buf/dma-fence.c
>> +++ b/drivers/dma-buf/dma-fence.c
>> @@ -208,6 +208,9 @@ dma_fence_wait_timeout(struct dma_fence *fence, bool intr, signed long timeout)
>>       if (WARN_ON(timeout < 0))
>>           return -EINVAL;
>>   +    if (timeout > 0)
>> +        might_sleep();
>> +
>
> I would rather like to see might_sleep() called here all the time even with timeout==0.
>
> IIRC I removed the code in TTM abusing this in atomic context quite a while ago, but could be that some leaked in again or it is called in atomic context elsewhere as well. 


Same, glad I'm not the only one who wants it. :)

~Maarten