[PATCH] drm/sched: fix the bug of time out calculation(v3)

[Andrey Grodzovsky]

On 2021-08-26 12:55 a.m., Monk Liu wrote:
> issue:
> in cleanup_job the cancle_delayed_work will cancel a TO timer
> even the its corresponding job is still running.
>
> fix:
> do not cancel the timer in cleanup_job, instead do the cancelling
> only when the heading job is signaled, and if there is a "next" job
> we start_timeout again.
>
> v2:
> further cleanup the logic, and do the TDR timer cancelling if the signaled job
> is the last one in its scheduler.
>
> v3:
> change the issue description
> remove the cancel_delayed_work in the begining of the cleanup_job
> recover the implement of drm_sched_job_begin.
>
> TODO:
> 1)introduce pause/resume scheduler in job_timeout to serial the handling
> of scheduler and job_timeout.
> 2)drop the bad job's del and insert in scheduler due to above serialization
> (no race issue anymore with the serialization)
>
> Signed-off-by: Monk Liu <Monk.Liu at amd.com>
> ---
>   drivers/gpu/drm/scheduler/sched_main.c | 25 ++++++++++---------------
>   1 file changed, 10 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index a2a9536..ecf8140 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -676,13 +676,7 @@ drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched)
>   {
>   	struct drm_sched_job *job, *next;
>   
> -	/*
> -	 * Don't destroy jobs while the timeout worker is running  OR thread
> -	 * is being parked and hence assumed to not touch pending_list
> -	 */
> -	if ((sched->timeout != MAX_SCHEDULE_TIMEOUT &&
> -	    !cancel_delayed_work(&sched->work_tdr)) ||
> -	    kthread_should_park())
> +	if (kthread_should_park())
>   		return NULL;


I actually don't see why we need to keep the above,
on the other side (in drm_sched_stop) we won't touch the pending list
anyway until sched thread came to full stop (kthread_park). If you do 
see a reason why
this needed then a comment should be here i think.

Andrey


>   
>   	spin_lock(&sched->job_list_lock);
> @@ -693,17 +687,21 @@ drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched)
>   	if (job && dma_fence_is_signaled(&job->s_fence->finished)) {
>   		/* remove job from pending_list */
>   		list_del_init(&job->list);
> +
> +		/* cancel this job's TO timer */
> +		cancel_delayed_work(&sched->work_tdr);
>   		/* make the scheduled timestamp more accurate */
>   		next = list_first_entry_or_null(&sched->pending_list,
>   						typeof(*next), list);
> -		if (next)
> +
> +		if (next) {
>   			next->s_fence->scheduled.timestamp =
>   				job->s_fence->finished.timestamp;
> -
> +			/* start TO timer for next job */
> +			drm_sched_start_timeout(sched);
> +		}
>   	} else {
>   		job = NULL;
> -		/* queue timeout for next job */
> -		drm_sched_start_timeout(sched);
>   	}
>   
>   	spin_unlock(&sched->job_list_lock);
> @@ -791,11 +789,8 @@ static int drm_sched_main(void *param)
>   					  (entity = drm_sched_select_entity(sched))) ||
>   					 kthread_should_stop());
>   
> -		if (cleanup_job) {
> +		if (cleanup_job)
>   			sched->ops->free_job(cleanup_job);
> -			/* queue timeout for next job */
> -			drm_sched_start_timeout(sched);
> -		}
>   
>   		if (!entity)
>   			continue;