6.11-stable review patch. If anyone has any objections, please let me know.
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From: Rob Clark robdclark@chromium.org
commit 440d52b370b03b366fd26ace36bab20552116145 upstream.
Fixes a race condition reported here: https://github.com/AsahiLinux/linux/issues/309#issuecomment-2238968609
The whole premise of lockless access to a single-producer-single- consumer queue is that there is just a single producer and single consumer. That means we can't call drm_sched_can_queue() (which is about queueing more work to the hw, not to the spsc queue) from anywhere other than the consumer (wq).
This call in the producer is just an optimization to avoid scheduling the consuming worker if it cannot yet queue more work to the hw. It is safe to drop this optimization to avoid the race condition.
Suggested-by: Asahi Lina lina@asahilina.net Fixes: a78422e9dff3 ("drm/sched: implement dynamic job-flow control") Closes: https://github.com/AsahiLinux/linux/issues/309 Cc: stable@vger.kernel.org Signed-off-by: Rob Clark robdclark@chromium.org Reviewed-by: Danilo Krummrich dakr@kernel.org Tested-by: Janne Grunau j@jannau.net Signed-off-by: Danilo Krummrich dakr@kernel.org Link: https://patchwork.freedesktop.org/patch/msgid/20240913202301.16772-1-robdcla... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/gpu/drm/scheduler/sched_entity.c | 4 ++-- drivers/gpu/drm/scheduler/sched_main.c | 7 ++----- include/drm/gpu_scheduler.h | 2 +- 3 files changed, 5 insertions(+), 8 deletions(-)
--- a/drivers/gpu/drm/scheduler/sched_entity.c +++ b/drivers/gpu/drm/scheduler/sched_entity.c @@ -380,7 +380,7 @@ static void drm_sched_entity_wakeup(stru container_of(cb, struct drm_sched_entity, cb);
drm_sched_entity_clear_dep(f, cb); - drm_sched_wakeup(entity->rq->sched, entity); + drm_sched_wakeup(entity->rq->sched); }
/** @@ -612,7 +612,7 @@ void drm_sched_entity_push_job(struct dr if (drm_sched_policy == DRM_SCHED_POLICY_FIFO) drm_sched_rq_update_fifo(entity, submit_ts);
- drm_sched_wakeup(entity->rq->sched, entity); + drm_sched_wakeup(entity->rq->sched); } } EXPORT_SYMBOL(drm_sched_entity_push_job); --- a/drivers/gpu/drm/scheduler/sched_main.c +++ b/drivers/gpu/drm/scheduler/sched_main.c @@ -1022,15 +1022,12 @@ EXPORT_SYMBOL(drm_sched_job_cleanup); /** * drm_sched_wakeup - Wake up the scheduler if it is ready to queue * @sched: scheduler instance - * @entity: the scheduler entity * * Wake up the scheduler if we can queue jobs. */ -void drm_sched_wakeup(struct drm_gpu_scheduler *sched, - struct drm_sched_entity *entity) +void drm_sched_wakeup(struct drm_gpu_scheduler *sched) { - if (drm_sched_can_queue(sched, entity)) - drm_sched_run_job_queue(sched); + drm_sched_run_job_queue(sched); }
/** --- a/include/drm/gpu_scheduler.h +++ b/include/drm/gpu_scheduler.h @@ -574,7 +574,7 @@ void drm_sched_entity_modify_sched(struc
void drm_sched_tdr_queue_imm(struct drm_gpu_scheduler *sched); void drm_sched_job_cleanup(struct drm_sched_job *job); -void drm_sched_wakeup(struct drm_gpu_scheduler *sched, struct drm_sched_entity *entity); +void drm_sched_wakeup(struct drm_gpu_scheduler *sched); bool drm_sched_wqueue_ready(struct drm_gpu_scheduler *sched); void drm_sched_wqueue_stop(struct drm_gpu_scheduler *sched); void drm_sched_wqueue_start(struct drm_gpu_scheduler *sched);