From: <gregkh@linuxfoundation.org> To: airlied@linux.ie, chris@chris-wilson.co.uk, daniel@ffwll.ch, dri-devel@lists.freedesktop.org, greg@kroah.com, gregkh@linuxfoundation.org, intel-gfx@lists.freedesktop.org, jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com, sultan@kerneltoast.com Cc: stable-commits@vger.kernel.org Subject: Patch "drm/i915: Fix ref->mutex deadlock in i915_active_wait()" has been added to the 5.4-stable tree Date: Fri, 10 Apr 2020 13:46:53 +0200 [thread overview] Message-ID: <1586519213118220@kroah.com> (raw) In-Reply-To: <20200407071809.3148-1-sultan@kerneltoast.com> This is a note to let you know that I've just added the patch titled drm/i915: Fix ref->mutex deadlock in i915_active_wait() to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-i915-fix-ref-mutex-deadlock-in-i915_active_wait.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@vger.kernel.org> know about it. From sultan@kerneltoast.com Fri Apr 10 11:07:34 2020 From: Sultan Alsawaf <sultan@kerneltoast.com> Date: Tue, 7 Apr 2020 00:18:09 -0700 Subject: drm/i915: Fix ref->mutex deadlock in i915_active_wait() To: Greg KH <greg@kroah.com> Cc: stable@vger.kernel.org, Jani Nikula <jani.nikula@linux.intel.com>, Joonas Lahtinen <joonas.lahtinen@linux.intel.com>, Rodrigo Vivi <rodrigo.vivi@intel.com>, David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>, Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Sultan Alsawaf <sultan@kerneltoast.com> Message-ID: <20200407071809.3148-1-sultan@kerneltoast.com> From: Sultan Alsawaf <sultan@kerneltoast.com> The following deadlock exists in i915_active_wait() due to a double lock on ref->mutex (call chain listed in order from top to bottom): i915_active_wait(); mutex_lock_interruptible(&ref->mutex); <-- ref->mutex first acquired i915_active_request_retire(); node_retire(); active_retire(); mutex_lock_nested(&ref->mutex, SINGLE_DEPTH_NESTING); <-- DEADLOCK Fix the deadlock by skipping the second ref->mutex lock when active_retire() is called through i915_active_request_retire(). Note that this bug only affects 5.4 and has since been fixed in 5.5. Normally, a backport of the fix from 5.5 would be in order, but the patch set that fixes this deadlock involves massive changes that are neither feasible nor desirable for backporting [1][2][3]. Therefore, this small patch was made to address the deadlock specifically for 5.4. [1] 274cbf20fd10 ("drm/i915: Push the i915_active.retire into a worker") [2] 093b92287363 ("drm/i915: Split i915_active.mutex into an irq-safe spinlock for the rbtree") [3] 750bde2fd4ff ("drm/i915: Serialise with remote retirement") Fixes: 12c255b5dad1 ("drm/i915: Provide an i915_active.acquire callback") Cc: <stable@vger.kernel.org> # 5.4.x Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/gpu/drm/i915/i915_active.c | 27 +++++++++++++++++++++++---- drivers/gpu/drm/i915/i915_active.h | 4 ++-- 2 files changed, 25 insertions(+), 6 deletions(-) --- a/drivers/gpu/drm/i915/i915_active.c +++ b/drivers/gpu/drm/i915/i915_active.c @@ -120,13 +120,17 @@ static inline void debug_active_assert(s #endif +#define I915_ACTIVE_RETIRE_NOLOCK BIT(0) + static void __active_retire(struct i915_active *ref) { struct active_node *it, *n; struct rb_root root; bool retire = false; + unsigned long bits; + ref = ptr_unpack_bits(ref, &bits, 2); lockdep_assert_held(&ref->mutex); /* return the unused nodes to our slabcache -- flushing the allocator */ @@ -138,7 +142,8 @@ __active_retire(struct i915_active *ref) retire = true; } - mutex_unlock(&ref->mutex); + if (!(bits & I915_ACTIVE_RETIRE_NOLOCK)) + mutex_unlock(&ref->mutex); if (!retire) return; @@ -155,13 +160,18 @@ __active_retire(struct i915_active *ref) static void active_retire(struct i915_active *ref) { + struct i915_active *ref_packed = ref; + unsigned long bits; + + ref = ptr_unpack_bits(ref, &bits, 2); GEM_BUG_ON(!atomic_read(&ref->count)); if (atomic_add_unless(&ref->count, -1, 1)) return; /* One active may be flushed from inside the acquire of another */ - mutex_lock_nested(&ref->mutex, SINGLE_DEPTH_NESTING); - __active_retire(ref); + if (!(bits & I915_ACTIVE_RETIRE_NOLOCK)) + mutex_lock_nested(&ref->mutex, SINGLE_DEPTH_NESTING); + __active_retire(ref_packed); } static void @@ -170,6 +180,14 @@ node_retire(struct i915_active_request * active_retire(node_from_active(base)->ref); } +static void +node_retire_nolock(struct i915_active_request *base, struct i915_request *rq) +{ + struct i915_active *ref = node_from_active(base)->ref; + + active_retire(ptr_pack_bits(ref, I915_ACTIVE_RETIRE_NOLOCK, 2)); +} + static struct i915_active_request * active_instance(struct i915_active *ref, struct intel_timeline *tl) { @@ -421,7 +439,8 @@ int i915_active_wait(struct i915_active break; } - err = i915_active_request_retire(&it->base, BKL(ref)); + err = i915_active_request_retire(&it->base, BKL(ref), + node_retire_nolock); if (err) break; } --- a/drivers/gpu/drm/i915/i915_active.h +++ b/drivers/gpu/drm/i915/i915_active.h @@ -309,7 +309,7 @@ i915_active_request_isset(const struct i */ static inline int __must_check i915_active_request_retire(struct i915_active_request *active, - struct mutex *mutex) + struct mutex *mutex, i915_active_retire_fn retire) { struct i915_request *request; long ret; @@ -327,7 +327,7 @@ i915_active_request_retire(struct i915_a list_del_init(&active->link); RCU_INIT_POINTER(active->request, NULL); - active->retire(active, request); + retire(active, request); return 0; } Patches currently in stable-queue which might be from sultan@kerneltoast.com are queue-5.4/drm-i915-fix-ref-mutex-deadlock-in-i915_active_wait.patch _______________________________________________ dri-devel mailing list dri-devel@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/dri-devel
WARNING: multiple messages have this Message-ID (diff)
From: <gregkh@linuxfoundation.org> To: airlied@linux.ie, chris@chris-wilson.co.uk, daniel@ffwll.ch, dri-devel@lists.freedesktop.org, greg@kroah.com, gregkh@linuxfoundation.org, intel-gfx@lists.freedesktop.org, jani.nikula@linux.intel.com, joonas.lahtinen@linux.intel.com, rodrigo.vivi@intel.com, sultan@kerneltoast.com Cc: stable-commits@vger.kernel.org Subject: [Intel-gfx] Patch "drm/i915: Fix ref->mutex deadlock in i915_active_wait()" has been added to the 5.4-stable tree Date: Fri, 10 Apr 2020 13:46:53 +0200 [thread overview] Message-ID: <1586519213118220@kroah.com> (raw) In-Reply-To: <20200407071809.3148-1-sultan@kerneltoast.com> This is a note to let you know that I've just added the patch titled drm/i915: Fix ref->mutex deadlock in i915_active_wait() to the 5.4-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary The filename of the patch is: drm-i915-fix-ref-mutex-deadlock-in-i915_active_wait.patch and it can be found in the queue-5.4 subdirectory. If you, or anyone else, feels it should not be added to the stable tree, please let <stable@vger.kernel.org> know about it. From sultan@kerneltoast.com Fri Apr 10 11:07:34 2020 From: Sultan Alsawaf <sultan@kerneltoast.com> Date: Tue, 7 Apr 2020 00:18:09 -0700 Subject: drm/i915: Fix ref->mutex deadlock in i915_active_wait() To: Greg KH <greg@kroah.com> Cc: stable@vger.kernel.org, Jani Nikula <jani.nikula@linux.intel.com>, Joonas Lahtinen <joonas.lahtinen@linux.intel.com>, Rodrigo Vivi <rodrigo.vivi@intel.com>, David Airlie <airlied@linux.ie>, Daniel Vetter <daniel@ffwll.ch>, Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, Sultan Alsawaf <sultan@kerneltoast.com> Message-ID: <20200407071809.3148-1-sultan@kerneltoast.com> From: Sultan Alsawaf <sultan@kerneltoast.com> The following deadlock exists in i915_active_wait() due to a double lock on ref->mutex (call chain listed in order from top to bottom): i915_active_wait(); mutex_lock_interruptible(&ref->mutex); <-- ref->mutex first acquired i915_active_request_retire(); node_retire(); active_retire(); mutex_lock_nested(&ref->mutex, SINGLE_DEPTH_NESTING); <-- DEADLOCK Fix the deadlock by skipping the second ref->mutex lock when active_retire() is called through i915_active_request_retire(). Note that this bug only affects 5.4 and has since been fixed in 5.5. Normally, a backport of the fix from 5.5 would be in order, but the patch set that fixes this deadlock involves massive changes that are neither feasible nor desirable for backporting [1][2][3]. Therefore, this small patch was made to address the deadlock specifically for 5.4. [1] 274cbf20fd10 ("drm/i915: Push the i915_active.retire into a worker") [2] 093b92287363 ("drm/i915: Split i915_active.mutex into an irq-safe spinlock for the rbtree") [3] 750bde2fd4ff ("drm/i915: Serialise with remote retirement") Fixes: 12c255b5dad1 ("drm/i915: Provide an i915_active.acquire callback") Cc: <stable@vger.kernel.org> # 5.4.x Signed-off-by: Sultan Alsawaf <sultan@kerneltoast.com> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> --- drivers/gpu/drm/i915/i915_active.c | 27 +++++++++++++++++++++++---- drivers/gpu/drm/i915/i915_active.h | 4 ++-- 2 files changed, 25 insertions(+), 6 deletions(-) --- a/drivers/gpu/drm/i915/i915_active.c +++ b/drivers/gpu/drm/i915/i915_active.c @@ -120,13 +120,17 @@ static inline void debug_active_assert(s #endif +#define I915_ACTIVE_RETIRE_NOLOCK BIT(0) + static void __active_retire(struct i915_active *ref) { struct active_node *it, *n; struct rb_root root; bool retire = false; + unsigned long bits; + ref = ptr_unpack_bits(ref, &bits, 2); lockdep_assert_held(&ref->mutex); /* return the unused nodes to our slabcache -- flushing the allocator */ @@ -138,7 +142,8 @@ __active_retire(struct i915_active *ref) retire = true; } - mutex_unlock(&ref->mutex); + if (!(bits & I915_ACTIVE_RETIRE_NOLOCK)) + mutex_unlock(&ref->mutex); if (!retire) return; @@ -155,13 +160,18 @@ __active_retire(struct i915_active *ref) static void active_retire(struct i915_active *ref) { + struct i915_active *ref_packed = ref; + unsigned long bits; + + ref = ptr_unpack_bits(ref, &bits, 2); GEM_BUG_ON(!atomic_read(&ref->count)); if (atomic_add_unless(&ref->count, -1, 1)) return; /* One active may be flushed from inside the acquire of another */ - mutex_lock_nested(&ref->mutex, SINGLE_DEPTH_NESTING); - __active_retire(ref); + if (!(bits & I915_ACTIVE_RETIRE_NOLOCK)) + mutex_lock_nested(&ref->mutex, SINGLE_DEPTH_NESTING); + __active_retire(ref_packed); } static void @@ -170,6 +180,14 @@ node_retire(struct i915_active_request * active_retire(node_from_active(base)->ref); } +static void +node_retire_nolock(struct i915_active_request *base, struct i915_request *rq) +{ + struct i915_active *ref = node_from_active(base)->ref; + + active_retire(ptr_pack_bits(ref, I915_ACTIVE_RETIRE_NOLOCK, 2)); +} + static struct i915_active_request * active_instance(struct i915_active *ref, struct intel_timeline *tl) { @@ -421,7 +439,8 @@ int i915_active_wait(struct i915_active break; } - err = i915_active_request_retire(&it->base, BKL(ref)); + err = i915_active_request_retire(&it->base, BKL(ref), + node_retire_nolock); if (err) break; } --- a/drivers/gpu/drm/i915/i915_active.h +++ b/drivers/gpu/drm/i915/i915_active.h @@ -309,7 +309,7 @@ i915_active_request_isset(const struct i */ static inline int __must_check i915_active_request_retire(struct i915_active_request *active, - struct mutex *mutex) + struct mutex *mutex, i915_active_retire_fn retire) { struct i915_request *request; long ret; @@ -327,7 +327,7 @@ i915_active_request_retire(struct i915_a list_del_init(&active->link); RCU_INIT_POINTER(active->request, NULL); - active->retire(active, request); + retire(active, request); return 0; } Patches currently in stable-queue which might be from sultan@kerneltoast.com are queue-5.4/drm-i915-fix-ref-mutex-deadlock-in-i915_active_wait.patch _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
next prev parent reply other threads:[~2020-04-10 11:47 UTC|newest] Thread overview: 55+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-04-07 6:26 [PATCH 0/1] drm/i915: Fix a deadlock that only affects 5.4 Sultan Alsawaf 2020-04-07 6:26 ` [PATCH 1/1] drm/i915: Fix ref->mutex deadlock in i915_active_wait() Sultan Alsawaf 2020-04-14 8:13 ` Chris Wilson 2020-04-14 8:13 ` [Intel-gfx] " Chris Wilson 2020-04-14 8:13 ` Chris Wilson 2020-04-14 14:52 ` Sultan Alsawaf 2020-04-14 14:52 ` [Intel-gfx] " Sultan Alsawaf 2020-04-14 14:52 ` Sultan Alsawaf 2020-04-07 6:52 ` [PATCH 0/1] drm/i915: Fix a deadlock that only affects 5.4 Greg KH 2020-04-07 6:52 ` [Intel-gfx] " Greg KH 2020-04-07 6:52 ` Greg KH 2020-04-07 7:18 ` [PATCH v2] drm/i915: Fix ref->mutex deadlock in i915_active_wait() Sultan Alsawaf 2020-04-07 20:32 ` [PATCH v3] " Sultan Alsawaf 2020-04-11 11:39 ` Patch "drm/i915: Fix ref->mutex deadlock in i915_active_wait()" has been added to the 5.4-stable tree gregkh 2020-04-11 11:39 ` [Intel-gfx] " gregkh 2020-04-11 11:59 ` [Intel-gfx] ✗ Fi.CI.BUILD: failure for Patch "drm/i915: Fix ref->mutex deadlock in i915_active_wait()" has been added to the 5.4-stable tree (rev2) Patchwork 2020-04-10 9:08 ` [PATCH v2] drm/i915: Fix ref->mutex deadlock in i915_active_wait() Greg KH 2020-04-10 9:08 ` [Intel-gfx] " Greg KH 2020-04-10 9:08 ` Greg KH 2020-04-10 14:15 ` Sultan Alsawaf 2020-04-10 14:15 ` [Intel-gfx] " Sultan Alsawaf 2020-04-10 14:15 ` Sultan Alsawaf 2020-04-10 14:17 ` Sultan Alsawaf 2020-04-10 14:17 ` [Intel-gfx] " Sultan Alsawaf 2020-04-10 14:17 ` Sultan Alsawaf 2020-04-11 11:39 ` Greg KH 2020-04-11 11:39 ` [Intel-gfx] " Greg KH 2020-04-11 11:39 ` Greg KH 2020-04-14 8:15 ` Chris Wilson 2020-04-14 8:15 ` [Intel-gfx] " Chris Wilson 2020-04-14 8:15 ` Chris Wilson 2020-04-14 8:23 ` Greg KH 2020-04-14 8:23 ` [Intel-gfx] " Greg KH 2020-04-14 8:23 ` Greg KH 2020-04-20 9:02 ` Joonas Lahtinen 2020-04-20 9:02 ` [Intel-gfx] " Joonas Lahtinen 2020-04-20 9:02 ` Joonas Lahtinen 2020-04-20 15:42 ` Sultan Alsawaf 2020-04-20 15:42 ` [Intel-gfx] " Sultan Alsawaf 2020-04-20 15:42 ` Sultan Alsawaf 2020-04-21 8:04 ` Joonas Lahtinen 2020-04-21 8:04 ` [Intel-gfx] " Joonas Lahtinen 2020-04-21 8:04 ` Joonas Lahtinen 2020-04-21 16:38 ` Sultan Alsawaf 2020-04-21 16:38 ` [Intel-gfx] " Sultan Alsawaf 2020-04-21 16:38 ` Sultan Alsawaf 2020-04-21 20:55 ` Jason A. Donenfeld 2020-04-21 20:55 ` [Intel-gfx] " Jason A. Donenfeld 2020-04-21 20:55 ` Jason A. Donenfeld 2020-04-14 14:35 ` Sultan Alsawaf 2020-04-14 14:35 ` [Intel-gfx] " Sultan Alsawaf 2020-04-14 14:35 ` Sultan Alsawaf 2020-04-10 11:46 ` gregkh [this message] 2020-04-10 11:46 ` [Intel-gfx] Patch "drm/i915: Fix ref->mutex deadlock in i915_active_wait()" has been added to the 5.4-stable tree gregkh 2020-04-10 11:56 ` [Intel-gfx] ✗ Fi.CI.BUILD: failure for " Patchwork
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