From d25e3a610bae03bffc5c14b5d944a5d0cd844678 Mon Sep 17 00:00:00 2001 From: Philipp Stanner Date: Wed, 22 Oct 2025 08:34:03 +0200 Subject: drm/sched: Fix race in drm_sched_entity_select_rq() In a past bug fix it was forgotten that entity access must be protected by the entity lock. That's a data race and potentially UB. Move the spin_unlock() to the appropriate position. Cc: stable@vger.kernel.org # v5.13+ Fixes: ac4eb83ab255 ("drm/sched: select new rq even if there is only one v3") Reviewed-by: Tvrtko Ursulin Signed-off-by: Philipp Stanner Link: https://patch.msgid.link/20251022063402.87318-2-phasta@kernel.org --- drivers/gpu/drm/scheduler/sched_entity.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'drivers/gpu/drm/scheduler') diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c index 5a4697f636f2..aa222166de58 100644 --- a/drivers/gpu/drm/scheduler/sched_entity.c +++ b/drivers/gpu/drm/scheduler/sched_entity.c @@ -552,10 +552,11 @@ void drm_sched_entity_select_rq(struct drm_sched_entity *entity) drm_sched_rq_remove_entity(entity->rq, entity); entity->rq = rq; } - spin_unlock(&entity->lock); if (entity->num_sched_list == 1) entity->sched_list = NULL; + + spin_unlock(&entity->lock); } /** -- cgit v1.2.3 From 9e8b3201c7302d5b522ba3535630bed21cc03c27 Mon Sep 17 00:00:00 2001 From: David Rosca Date: Wed, 15 Oct 2025 16:01:28 +0200 Subject: drm/sched: avoid killing parent entity on child SIGKILL MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The DRM scheduler tracks who last uses an entity and when that process is killed blocks all further submissions to that entity. The problem is that we didn't track who initially created an entity, so when a process accidently leaked its file descriptor to a child and that child got killed, we killed the parent's entities. Avoid that and instead initialize the entities last user on entity creation. This also allows to drop the extra NULL check. Signed-off-by: David Rosca Signed-off-by: Christian König Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/4568 Reviewed-by: Alex Deucher CC: stable@vger.kernel.org Acked-by: Philipp Stanner Link: https://lore.kernel.org/r/20251015140128.1470-1-christian.koenig@amd.com Signed-off-by: Philipp Stanner Link: https://patch.msgid.link/20251015140128.1470-1-christian.koenig@amd.com --- drivers/gpu/drm/scheduler/sched_entity.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'drivers/gpu/drm/scheduler') diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c index aa222166de58..c8e949f4a568 100644 --- a/drivers/gpu/drm/scheduler/sched_entity.c +++ b/drivers/gpu/drm/scheduler/sched_entity.c @@ -70,6 +70,7 @@ int drm_sched_entity_init(struct drm_sched_entity *entity, entity->guilty = guilty; entity->num_sched_list = num_sched_list; entity->priority = priority; + entity->last_user = current->group_leader; /* * It's perfectly valid to initialize an entity without having a valid * scheduler attached. It's just not valid to use the scheduler before it @@ -302,7 +303,7 @@ long drm_sched_entity_flush(struct drm_sched_entity *entity, long timeout) /* For a killed process disallow further enqueueing of jobs. */ last_user = cmpxchg(&entity->last_user, current->group_leader, NULL); - if ((!last_user || last_user == current->group_leader) && + if (last_user == current->group_leader && (current->flags & PF_EXITING) && (current->exit_code == SIGKILL)) drm_sched_entity_kill(entity); -- cgit v1.2.3 From 487df8b698345dd5a91346335f05170ed5f29d4e Mon Sep 17 00:00:00 2001 From: Pierre-Eric Pelloux-Prayer Date: Tue, 4 Nov 2025 10:53:57 +0100 Subject: 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(-) (limited to 'drivers/gpu/drm/scheduler') 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); } -- cgit v1.2.3