[PATCH] drm/scheduler: fix inconsistent locking of job_list_lock
Lucas Stach
l.stach at pengutronix.de
Fri Mar 13 14:51:30 UTC 2020
Hi Alex,
since you seem to be picking up scheduler patches, can I ask you to
take this one through your tree?
Regards,
Lucas
On Mo, 2020-01-20 at 11:59 +0100, Christian König wrote:
> Am 20.01.20 um 11:51 schrieb Lucas Stach:
> > 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.
> >
> > Signed-off-by: Lucas Stach <l.stach at pengutronix.de>
>
> Reviewed-by: Christian König <christian.koenig at amd.com>, do you want to
> merge through drm-misc-next or should I push it to amd-staging-drm-next?
>
> Regards,
> Christian.
>
> > ---
> > drivers/gpu/drm/scheduler/sched_main.c | 38 ++++++++++----------------
> > 1 file changed, 15 insertions(+), 23 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> > index 3c57e84222ca..d1b24444dd99 100644
> > --- a/drivers/gpu/drm/scheduler/sched_main.c
> > +++ b/drivers/gpu/drm/scheduler/sched_main.c
> > @@ -220,8 +220,7 @@ 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
> > *
> > @@ -250,43 +249,39 @@ 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);
> > +
> > job = list_first_entry_or_null(&sched->ring_mirror_list,
> > struct drm_sched_job, node);
> >
> > @@ -303,9 +298,9 @@ static void drm_sched_job_timedout(struct work_struct *work)
> > }
> > }
> >
> > - 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);
> > }
> >
> > /**
> > @@ -368,7 +363,6 @@ 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);
> >
> > @@ -388,9 +382,9 @@ 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
> > @@ -433,7 +427,6 @@ 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;
> >
> > /*
> > @@ -462,9 +455,9 @@ 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);
> > @@ -648,7 +641,6 @@ 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
> > @@ -659,7 +651,7 @@ 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);
> > @@ -673,7 +665,7 @@ 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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