From 487df8b698345dd5a91346335f05170ed5f29d4e Mon Sep 17 00:00:00 2001 From: Pierre-Eric Pelloux-Prayer Date: Tue, 4 Nov 2025 10:53:57 +0100 Subject: [PATCH 5364/5403] drm/sched: Fix deadlock in drm_sched_entity_kill_jobs_cb MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The Mesa issue referenced below pointed out a possible deadlock: [ 1231.611031] Possible interrupt unsafe locking scenario: [ 1231.611033] CPU0 CPU1 [ 1231.611034] ---- ---- [ 1231.611035] lock(&xa->xa_lock#17); [ 1231.611038] local_irq_disable(); [ 1231.611039] lock(&fence->lock); [ 1231.611041] lock(&xa->xa_lock#17); [ 1231.611044] [ 1231.611045] lock(&fence->lock); [ 1231.611047] *** DEADLOCK *** In this example, CPU0 would be any function accessing job->dependencies through the xa_* functions that don't disable interrupts (eg: drm_sched_job_add_dependency(), drm_sched_entity_kill_jobs_cb()). CPU1 is executing drm_sched_entity_kill_jobs_cb() as a fence signalling callback so in an interrupt context. It will deadlock when trying to grab the xa_lock which is already held by CPU0. Replacing all xa_* usage by their xa_*_irq counterparts would fix this issue, but Christian pointed out another issue: dma_fence_signal takes fence.lock and so does dma_fence_add_callback. dma_fence_signal() // locks f1.lock -> drm_sched_entity_kill_jobs_cb() -> foreach dependencies -> dma_fence_add_callback() // locks f2.lock This will deadlock if f1 and f2 share the same spinlock. To fix both issues, the code iterating on dependencies and re-arming them is moved out to drm_sched_entity_kill_jobs_work(). Cc: stable@vger.kernel.org # v6.2+ Fixes: 2fdb8a8f07c2 ("drm/scheduler: rework entity flush, kill and fini") Link: https://gitlab.freedesktop.org/mesa/mesa/-/issues/13908 Reported-by: Mikhail Gavrilov Suggested-by: Christian König Reviewed-by: Christian König Signed-off-by: Pierre-Eric Pelloux-Prayer [phasta: commit message nits] Signed-off-by: Philipp Stanner Link: https://patch.msgid.link/20251104095358.15092-1-pierre-eric.pelloux-prayer@amd.com --- drivers/gpu/drm/scheduler/sched_entity.c | 34 +++++++++++++----------- 1 file changed, 19 insertions(+), 15 deletions(-) diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c index c8e949f4a568..fe174a4857be 100644 --- a/drivers/gpu/drm/scheduler/sched_entity.c +++ b/drivers/gpu/drm/scheduler/sched_entity.c @@ -173,26 +173,15 @@ int drm_sched_entity_error(struct drm_sched_entity *entity) } EXPORT_SYMBOL(drm_sched_entity_error); +static void drm_sched_entity_kill_jobs_cb(struct dma_fence *f, + struct dma_fence_cb *cb); + static void drm_sched_entity_kill_jobs_work(struct work_struct *wrk) { struct drm_sched_job *job = container_of(wrk, typeof(*job), work); - - drm_sched_fence_scheduled(job->s_fence, NULL); - drm_sched_fence_finished(job->s_fence, -ESRCH); - WARN_ON(job->s_fence->parent); - job->sched->ops->free_job(job); -} - -/* Signal the scheduler finished fence when the entity in question is killed. */ -static void drm_sched_entity_kill_jobs_cb(struct dma_fence *f, - struct dma_fence_cb *cb) -{ - struct drm_sched_job *job = container_of(cb, struct drm_sched_job, - finish_cb); + struct dma_fence *f; unsigned long index; - dma_fence_put(f); - /* Wait for all dependencies to avoid data corruptions */ xa_for_each(&job->dependencies, index, f) { struct drm_sched_fence *s_fence = to_drm_sched_fence(f); @@ -220,6 +209,21 @@ static void drm_sched_entity_kill_jobs_cb(struct dma_fence *f, dma_fence_put(f); } + drm_sched_fence_scheduled(job->s_fence, NULL); + drm_sched_fence_finished(job->s_fence, -ESRCH); + WARN_ON(job->s_fence->parent); + job->sched->ops->free_job(job); +} + +/* Signal the scheduler finished fence when the entity in question is killed. */ +static void drm_sched_entity_kill_jobs_cb(struct dma_fence *f, + struct dma_fence_cb *cb) +{ + struct drm_sched_job *job = container_of(cb, struct drm_sched_job, + finish_cb); + + dma_fence_put(f); + INIT_WORK(&job->work, drm_sched_entity_kill_jobs_work); schedule_work(&job->work); } -- 2.54.0