drm/scheduler: fix inconsistent locking of job_list_lock

1db8c142b6c5 (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: Christian König <christian.koenig@amd.com>
Signed-off-by: Lucas Stach <l.stach@pengutronix.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index 34231b7..bb53a80 100644 (file)
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -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;
 }