Am 25.11.19 um 17:51 schrieb Steven Price:
On 25/11/2019 14:10, Andrey Grodzovsky wrote:
When the sched thread is parked we assume ring_mirror_list is
not accessed from here.
FWIW I don't think this is necessary. kthread_park() will wait until the
thread is parked, at which point the thread is stuck in kthread_parkme()
until unparked.

So all this does is avoid waiting for any cleanup jobs before parking -
which might be a reasonable goal in itself, but if so lets at least
document that.

Now that you mention it that is indeed wrong.

The real problem is that in the main thread we mangled the call to kthread_parkme() into drm_sched_blocked() which can be called in atomic context.

I suggest to rework this so that the kthread_should_park() and kthread_should_stop() test in wait_event_interruptible() come first and then call kthread_parkme() outside of the wait_event_interruptible().

Regards,
Christian.


Steve

Signed-off-by: Andrey Grodzovsky <andrey.grodzov...@amd.com>
Reviewed-by: Christian König <christian.koe...@amd.com>
---
  drivers/gpu/drm/scheduler/sched_main.c | 10 +++++++---
  1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c 
b/drivers/gpu/drm/scheduler/sched_main.c
index d4cc728..6774955 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -635,9 +635,13 @@ 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 */
-       if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
-           !cancel_delayed_work(&sched->work_tdr))
+       /*
+       * Don't destroy jobs while the timeout worker is running  OR thread
+       * is being parked and hence assumed to not touch ring_mirror_list
+       */
+       if ((sched->timeout != MAX_SCHEDULE_TIMEOUT &&
+            !cancel_delayed_work(&sched->work_tdr)) ||
+            __kthread_should_park(sched->thread))
                return NULL;
spin_lock_irqsave(&sched->job_list_lock, flags);

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