From: Daniel Vetter <daniel.vetter@ffwll.ch>
To: DRI Development <dri-devel@lists.freedesktop.org>
Cc: "Daniel Vetter" <daniel.vetter@ffwll.ch>,
linux-media@vger.kernel.org, linaro-mm-sig@lists.linaro.org,
linux-rdma@vger.kernel.org, amd-gfx@lists.freedesktop.org,
intel-gfx@lists.freedesktop.org,
"Chris Wilson" <chris@chris-wilson.co.uk>,
"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
"Christian König" <christian.koenig@amd.com>,
"Daniel Vetter" <daniel.vetter@intel.com>
Subject: [PATCH] drm/amdgpu/dc: Stop dma_resv_lock inversion in commit_tail
Date: Mon, 27 Jul 2020 23:30:18 +0200 [thread overview]
Message-ID: <20200727213017.852589-1-daniel.vetter@ffwll.ch> (raw)
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.
v2: Also take into account tmz_surface boolean, plus just delete the
old 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>
---
DC-folks, I think this split out patch from my series here
https://lore.kernel.org/dri-devel/20200707201229.472834-1-daniel.vetter@ffwll.ch/
should be ready for review/merging. I fixed it up a bit so that it's not
just a gross hack :-)
Cheers, Daniel
---
.../gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c | 19 ++++++-------------
1 file changed, 6 insertions(+), 13 deletions(-)
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 21ec64fe5527..a20b62b1f2ef 100644
--- a/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
+++ b/drivers/gpu/drm/amd/display/amdgpu_dm/amdgpu_dm.c
@@ -6959,20 +6959,13 @@ static void amdgpu_dm_commit_planes(struct drm_atomic_state *state,
DRM_ERROR("Waiting for fences timed out!");
/*
- * TODO This might fail and hence better not used, wait
- * explicitly on fences instead
- * and in general should be called for
- * blocking commit to as per framework helpers
+ * We cannot reserve buffers here, which means the normal flag
+ * access functions don't work. Paper over this with READ_ONCE,
+ * but maybe the flags are invariant enough that not even that
+ * would be needed.
*/
- r = amdgpu_bo_reserve(abo, true);
- if (unlikely(r != 0))
- DRM_ERROR("failed to reserve buffer before flip\n");
-
- amdgpu_bo_get_tiling_flags(abo, &tiling_flags);
-
- tmz_surface = amdgpu_bo_encrypted(abo);
-
- amdgpu_bo_unreserve(abo);
+ tiling_flags = READ_ONCE(abo->tiling_flags);
+ tmz_surface = READ_ONCE(abo->flags) & AMDGPU_GEM_CREATE_ENCRYPTED;
fill_dc_plane_info_and_addr(
dm->adev, new_plane_state, tiling_flags,
--
2.27.0
next reply other threads:[~2020-07-27 21:31 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-27 21:30 Daniel Vetter [this message]
2020-07-28 6:56 ` [PATCH] drm/amdgpu/dc: Stop dma_resv_lock inversion in commit_tail Christian König
2020-07-29 22:10 ` Alex Deucher
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