Commit a7fbb630 authored by Lucas Stach's avatar Lucas Stach Committed by Alex Deucher
Browse files

drm/scheduler: fix inconsistent locking of job_list_lock 



1db8c142 (drm/scheduler: Add drm_sched_suspend/resume_timeout()) made
the job_list_lock IRQ safe in as the suspend/resume calls were expected to
be called from IRQ context. This usage never materialized in upstream.
Instead amdgpu started locking the job_list_lock in an IRQ unsafe way in
amdgpu_ib_preempt_mark_partial_job() and amdgpu_ib_preempt_job_recovery(),
which leads to potential deadlock if one would actually start to call the
drm_sched_suspend/resume_timeout functions from IRQ context.

As no current user needs the locking to be IRQ safe, the local IRQ
disable/enable is pure overhead. Fix the inconsistent locking by changing
all uses of job_list_lock to use the IRQ unsafe locking primitives.

Reviewed-by: default avatarChristian König <christian.koenig@amd.com>
Signed-off-by: default avatarLucas Stach <l.stach@pengutronix.de>
Signed-off-by: default avatarAlex Deucher <alexander.deucher@amd.com>
parent c2c91828

drivers/gpu/drm/scheduler/sched_main.c

+17 −26
Original line number Diff line number Diff line
@@ -222,8 +222,7 @@ EXPORT_SYMBOL(drm_sched_fault); 
 *

 * Suspend the delayed work timeout for the scheduler. This is done by

 * modifying the delayed work timeout to an arbitrary large value,

 * MAX_SCHEDULE_TIMEOUT in this case. Note that this function can be

 * called from an IRQ context.

 * MAX_SCHEDULE_TIMEOUT in this case.

 *

 * Returns the timeout remaining

 *
@@ -252,46 +251,41 @@ EXPORT_SYMBOL(drm_sched_suspend_timeout); 
 * @sched: scheduler instance for which to resume the timeout

 * @remaining: remaining timeout

 *

 * Resume the delayed work timeout for the scheduler. Note that

 * this function can be called from an IRQ context.

 * Resume the delayed work timeout for the scheduler.

 */

void drm_sched_resume_timeout(struct drm_gpu_scheduler *sched,

		unsigned long remaining)

{

	unsigned long flags;



	spin_lock_irqsave(&sched->job_list_lock, flags);

	spin_lock(&sched->job_list_lock);



	if (list_empty(&sched->ring_mirror_list))

		cancel_delayed_work(&sched->work_tdr);

	else

		mod_delayed_work(system_wq, &sched->work_tdr, remaining);



	spin_unlock_irqrestore(&sched->job_list_lock, flags);

	spin_unlock(&sched->job_list_lock);

}

EXPORT_SYMBOL(drm_sched_resume_timeout);



static void drm_sched_job_begin(struct drm_sched_job *s_job)

{

	struct drm_gpu_scheduler *sched = s_job->sched;

	unsigned long flags;



	spin_lock_irqsave(&sched->job_list_lock, flags);

	spin_lock(&sched->job_list_lock);

	list_add_tail(&s_job->node, &sched->ring_mirror_list);

	drm_sched_start_timeout(sched);

	spin_unlock_irqrestore(&sched->job_list_lock, flags);

	spin_unlock(&sched->job_list_lock);

}



static void drm_sched_job_timedout(struct work_struct *work)

{

	struct drm_gpu_scheduler *sched;

	struct drm_sched_job *job;

	unsigned long flags;



	sched = container_of(work, struct drm_gpu_scheduler, work_tdr.work);



	/* Protects against concurrent deletion in drm_sched_get_cleanup_job */

	spin_lock_irqsave(&sched->job_list_lock, flags);

	spin_lock(&sched->job_list_lock);

	job = list_first_entry_or_null(&sched->ring_mirror_list,

				       struct drm_sched_job, node);
@@ -302,7 +296,7 @@ static void drm_sched_job_timedout(struct work_struct *work) 
		 * is parked at which point it's safe.

		 */

		list_del_init(&job->node);

		spin_unlock_irqrestore(&sched->job_list_lock, flags);

		spin_unlock(&sched->job_list_lock);



		job->sched->ops->timedout_job(job);
@@ -315,12 +309,12 @@ static void drm_sched_job_timedout(struct work_struct *work) 
			sched->free_guilty = false;

		}

	} else {

		spin_unlock_irqrestore(&sched->job_list_lock, flags);

		spin_unlock(&sched->job_list_lock);

	}



	spin_lock_irqsave(&sched->job_list_lock, flags);

	spin_lock(&sched->job_list_lock);

	drm_sched_start_timeout(sched);

	spin_unlock_irqrestore(&sched->job_list_lock, flags);

	spin_unlock(&sched->job_list_lock);

}



 /**
@@ -383,7 +377,6 @@ EXPORT_SYMBOL(drm_sched_increase_karma); 
void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad)

{

	struct drm_sched_job *s_job, *tmp;

	unsigned long flags;



	kthread_park(sched->thread);
@@ -417,9 +410,9 @@ void drm_sched_stop(struct drm_gpu_scheduler *sched, struct drm_sched_job *bad) 
			 * remove job from ring_mirror_list.

			 * Locking here is for concurrent resume timeout

			 */

			spin_lock_irqsave(&sched->job_list_lock, flags);

			spin_lock(&sched->job_list_lock);

			list_del_init(&s_job->node);

			spin_unlock_irqrestore(&sched->job_list_lock, flags);

			spin_unlock(&sched->job_list_lock);



			/*

			 * Wait for job's HW fence callback to finish using s_job
@@ -462,7 +455,6 @@ EXPORT_SYMBOL(drm_sched_stop); 
void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery)

{

	struct drm_sched_job *s_job, *tmp;

	unsigned long flags;

	int r;



	/*
@@ -491,9 +483,9 @@ void drm_sched_start(struct drm_gpu_scheduler *sched, bool full_recovery) 
	}



	if (full_recovery) {

		spin_lock_irqsave(&sched->job_list_lock, flags);

		spin_lock(&sched->job_list_lock);

		drm_sched_start_timeout(sched);

		spin_unlock_irqrestore(&sched->job_list_lock, flags);

		spin_unlock(&sched->job_list_lock);

	}



	kthread_unpark(sched->thread);
@@ -677,7 +669,6 @@ static struct drm_sched_job * 
drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched)

{

	struct drm_sched_job *job;

	unsigned long flags;



	/*

	 * Don't destroy jobs while the timeout worker is running  OR thread
@@ -688,7 +679,7 @@ drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched) 
	    __kthread_should_park(sched->thread))

		return NULL;



	spin_lock_irqsave(&sched->job_list_lock, flags);

	spin_lock(&sched->job_list_lock);



	job = list_first_entry_or_null(&sched->ring_mirror_list,

				       struct drm_sched_job, node);
@@ -702,7 +693,7 @@ drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched) 
		drm_sched_start_timeout(sched);

	}



	spin_unlock_irqrestore(&sched->job_list_lock, flags);

	spin_unlock(&sched->job_list_lock);



	return job;

}

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