[PATCH] drm/sched: fix the bug of time out calculation(v2)

[Liu, Monk]

[AMD Official Use Only]

>>The timeout started by queue_delayed_work() in drm_sched_start_timeout() is paired with the cancel_delayed_work() in drm_sched_get_cleanup_job().

No that's wrong, see that when we are in cleanup_job(), assume we do not have timeout on this sched (we are just keep submitting new jobs to this sched),
Then the work_tdr is cancelled, and then we get the heading job, and let's assume the job is not signaled, then we run to the "queue timeout for next job" thus drm_sched_start_timeout() is called, so this heading job's TO timer is actually retriggered ... which is totally wrong.

With my patch the timer is already retriggered after previous JOB really signaled.

Can you be more specific on the incorrect part ?

Thanks 
------------------------------------------
Monk Liu | Cloud-GPU Core team
------------------------------------------

-----Original Message-----
From: Christian König <ckoenig.leichtzumerken at gmail.com> 
Sent: Wednesday, August 25, 2021 2:32 PM
To: Liu, Monk <Monk.Liu at amd.com>; amd-gfx at lists.freedesktop.org
Subject: Re: [PATCH] drm/sched: fix the bug of time out calculation(v2)

Well NAK to that approach. First of all your bug analyses is incorrect.

The timeout started by queue_delayed_work() in drm_sched_start_timeout() is paired with the cancel_delayed_work() in drm_sched_get_cleanup_job().

So you must have something else going on here.

Then please don't use mod_delayed_work(), instead always cancel it and restart it.

Regards,
Christian.

Am 25.08.21 um 06:14 schrieb Monk Liu:
> the original logic is wrong that the timeout will not be retriggerd 
> after the previous job siganled, and that lead to the scenario that 
> all jobs in the same scheduler shares the same timeout timer from the 
> very begining job in this scheduler which is wrong.
>
> we should modify the timer everytime a previous job signaled.
>
> v2:
> further cleanup the logic, and do the TDR timer cancelling if the 
> signaled job is the last one in its scheduler.
>
> Signed-off-by: Monk Liu <Monk.Liu at amd.com>
> ---
>   drivers/gpu/drm/scheduler/sched_main.c | 29 ++++++++++++++++++++---------
>   1 file changed, 20 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c 
> b/drivers/gpu/drm/scheduler/sched_main.c
> index a2a9536..8c102ac 100644
> --- a/drivers/gpu/drm/scheduler/sched_main.c
> +++ b/drivers/gpu/drm/scheduler/sched_main.c
> @@ -305,8 +305,17 @@ static void drm_sched_job_begin(struct drm_sched_job *s_job)
>   	struct drm_gpu_scheduler *sched = s_job->sched;
>   
>   	spin_lock(&sched->job_list_lock);
> -	list_add_tail(&s_job->list, &sched->pending_list);
> -	drm_sched_start_timeout(sched);
> +	if (list_empty(&sched->pending_list)) {
> +		list_add_tail(&s_job->list, &sched->pending_list);
> +		drm_sched_start_timeout(sched);
> +	} else {
> +		/* the old jobs in pending list are not finished yet
> +		 * no need to restart TDR timer here, it is already
> +		 * handled by drm_sched_get_cleanup_job
> +		 */
> +		list_add_tail(&s_job->list, &sched->pending_list);
> +	}
> +
>   	spin_unlock(&sched->job_list_lock);
>   }
>   
> @@ -693,17 +702,22 @@ 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);
> +
>   		/* make the scheduled timestamp more accurate */
>   		next = list_first_entry_or_null(&sched->pending_list,
>   						typeof(*next), list);
> -		if (next)
> +		if (next) {
> +			/* if we still have job in pending list we need modify the TDR timer */
> +			mod_delayed_work(system_wq, &sched->work_tdr, sched->timeout);
>   			next->s_fence->scheduled.timestamp =
>   				job->s_fence->finished.timestamp;
> +		} else {
> +			/* cancel the TDR timer if no job in pending list */
> +			cancel_delayed_work(&sched->work_tdr);
> +		}
>   
>   	} else {
>   		job = NULL;
> -		/* queue timeout for next job */
> -		drm_sched_start_timeout(sched);
>   	}
>   
>   	spin_unlock(&sched->job_list_lock);
> @@ -791,11 +805,8 @@ 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;