From b2b8af21fec35be417a3199b5a6c354605dd222a Mon Sep 17 00:00:00 2001 From: Pierre-Eric Pelloux-Prayer Date: Mon, 1 Sep 2025 14:40:32 +0200 Subject: [PATCH 4932/5403] drm/sched: Fix racy access to drm_sched_entity.dependency The drm_sched_job_unschedulable trace point can access entity->dependency after it was cleared by the callback installed in drm_sched_entity_add_dependency_cb, causing: BUG: kernel NULL pointer dereference, address: 0000000000000020 [...] Workqueue: comp_1.1.0 drm_sched_run_job_work [gpu_sched] RIP: 0010:trace_event_raw_event_drm_sched_job_unschedulable+0x70/0xd0 [gpu_sched] To fix this we either need to keep a reference to the fence before setting up the callbacks, or move the trace_drm_sched_job_unschedulable calls into drm_sched_entity_add_dependency_cb where they can be done earlier. Fixes: 76d97c870f29 ("drm/sched: Trace dependencies for GPU jobs") Signed-off-by: Pierre-Eric Pelloux-Prayer Reviewed-by: Tvrtko Ursulin Signed-off-by: Philipp Stanner Link: https://lore.kernel.org/r/20250901124032.1955-1-pierre-eric.pelloux-prayer@amd.com --- drivers/gpu/drm/scheduler/sched_entity.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) diff --git a/drivers/gpu/drm/scheduler/sched_entity.c b/drivers/gpu/drm/scheduler/sched_entity.c index 254932b9050e..5a4697f636f2 100644 --- a/drivers/gpu/drm/scheduler/sched_entity.c +++ b/drivers/gpu/drm/scheduler/sched_entity.c @@ -391,7 +391,8 @@ EXPORT_SYMBOL(drm_sched_entity_set_priority); * Add a callback to the current dependency of the entity to wake up the * scheduler when the entity becomes available. */ -static bool drm_sched_entity_add_dependency_cb(struct drm_sched_entity *entity) +static bool drm_sched_entity_add_dependency_cb(struct drm_sched_entity *entity, + struct drm_sched_job *sched_job) { struct drm_gpu_scheduler *sched = entity->rq->sched; struct dma_fence *fence = entity->dependency; @@ -421,6 +422,10 @@ static bool drm_sched_entity_add_dependency_cb(struct drm_sched_entity *entity) entity->dependency = fence; } + if (trace_drm_sched_job_unschedulable_enabled() && + !test_bit(DMA_FENCE_FLAG_SIGNALED_BIT, &entity->dependency->flags)) + trace_drm_sched_job_unschedulable(sched_job, entity->dependency); + if (!dma_fence_add_callback(entity->dependency, &entity->cb, drm_sched_entity_wakeup)) return true; @@ -461,10 +466,8 @@ struct drm_sched_job *drm_sched_entity_pop_job(struct drm_sched_entity *entity) while ((entity->dependency = drm_sched_job_dependency(sched_job, entity))) { - if (drm_sched_entity_add_dependency_cb(entity)) { - trace_drm_sched_job_unschedulable(sched_job, entity->dependency); + if (drm_sched_entity_add_dependency_cb(entity, sched_job)) return NULL; - } } /* skip jobs from entity that marked guilty */ -- 2.54.0