regression with d6c650c0a8f6f671e49553725e1db541376d95f2

[Christian König]

> There is chance that free_job() called before that 
> “trace_amd_sched_process_job”, correct?
>
Correct, but that is harmless.

Take a look what trace_amd_sched_process_job actually does, it just 
prints the pointer of the fence structure (but the pointer might be 
stale at this point).

Nevertheless you are right that this is really ugly.

How about the attached patch to fix the issue?

Regards,
Christian.

Am 13.10.2017 um 10:51 schrieb Liu, Monk:
>
> The free_job() is called in sched_job_finish() which is queued on a 
> WORK and scheduled from that “amd_sched_fence_finished()”
>
> So the finishing timing of free_job() is asynchronized with 
> sched_process_job()
>
> There is chance that free_job() called before that 
> “trace_amd_sched_process_job”, correct?
>
> And if so the s_fence referred by it maybe a wild pointer
>
> BR Monk
>
> *From:*Liu, Monk
> *Sent:* 2017年10月13日16:49
> *To:* Koenig, Christian <Christian.Koenig at amd.com>; Nicolai Hähnle 
> <nhaehnle at gmail.com>; amd-gfx at lists.freedesktop.org
> *Subject:* RE: regression with d6c650c0a8f6f671e49553725e1db541376d95f2
>
> No that’s not true
>
> The free_job() is called in sched_job_finish() which is queued on a 
> WORK and scheduled from that “amd_sched_fence_finished()”
>
> So the finishing timing of free_job() is asynchronized with 
> sched_process_job()
>
> How can you sure free_job() must before “trace_amd_sched_process_job”?
>
> *From:*Koenig, Christian
> *Sent:* 2017年10月13日16:43
> *To:* Liu, Monk <Monk.Liu at amd.com <mailto:Monk.Liu at amd.com>>; Nicolai 
> Hähnle <nhaehnle at gmail.com <mailto:nhaehnle at gmail.com>>; 
> amd-gfx at lists.freedesktop.org <mailto:amd-gfx at lists.freedesktop.org>
> *Subject:* Re: regression with d6c650c0a8f6f671e49553725e1db541376d95f2
>
> The free_job() callback is called only way after the job has finished.
>
> That is one change actually made by you to the code :)
>
> Christian.
>
> Am 13.10.2017 um 10:39 schrieb Liu, Monk:
>
>     I doubt it would always work fine…
>
>     First, we have FENCE_TRACE reference s_fence->finished after
>     “fence_signal(&fence->finished)”
>
>     Second, we have trace_amd_sched_proess_job(s_fence) after
>     “amd_sched_fence_finished()”,
>
>     If you put the finished before free_job() and by coincidence the
>     job_finish() get very soon executed you’ll have odds to hit wild
>     pointer on above two cases
>
>     BR Monk
>
>     *From:*Koenig, Christian
>     *Sent:* 2017年10月13日16:17
>     *To:* Liu, Monk <Monk.Liu at amd.com> <mailto:Monk.Liu at amd.com>;
>     Nicolai Hähnle <nhaehnle at gmail.com> <mailto:nhaehnle at gmail.com>;
>     amd-gfx at lists.freedesktop.org <mailto:amd-gfx at lists.freedesktop.org>
>     *Subject:* Re: regression with
>     d6c650c0a8f6f671e49553725e1db541376d95f2
>
>     Yeah, that change is actually incorrect and should be reverted.
>
>     What we really need to do is remove dropping sched_job->s_fence
>     from amd_sched_process_job() into amd_sched_job_finish() directly
>     before the call to free_job().
>
>     Regards,
>     Christian.
>
>     Am 13.10.2017 um 09:24 schrieb Liu, Monk:
>
>         commit d6c650c0a8f6f671e49553725e1db541376d95f2
>         Author: Nicolai Hähnle <nicolai.haehnle at amd.com>
>         <mailto:nicolai.haehnle at amd.com>
>         @@ -611,6 +611,10 @@ static int amd_sched_main(void *param)
>
>                         fence = sched->ops->run_job(sched_job);
>                         amd_sched_fence_scheduled(s_fence);
>         +
>         +               /* amd_sched_process_job drops the job's
>         reference of the fence. */
>         +               sched_job->s_fence = NULL;
>         +
>                         if (fence) {
>                                 s_fence->parent = dma_fence_get(fence);
>                                 r = dma_fence_add_callback(fence,
>         &s_fence->cb,
>
>         Hi Nicolai
>
>         with this patch, you will break
>         "amdgpu_sched_hw_job_reset()"routine:
>
>         void
>
>         amd_sched_hw_job_reset(structamd_gpu_scheduler
>
>         *sched)
>
>         {
>
>         structamd_sched_job
>
>         *s_job;
>
>         spin_lock(&sched->job_list_lock);
>
>         list_for_each_entry_reverse(s_job,
>
>         &sched->ring_mirror_list, node) {
>
>         if(s_job->s_fence->parent
>
>         &&
>
>         fence_remove_callback(s_job->s_fence->parent,
>
>         &s_job->s_fence->cb))
>
>         {
>
>         fence_put(s_job->s_fence->parent);
>
>                     s_job->s_fence->parent
>
>         =
>
>         NULL;
>
>         atomic_dec(&sched->hw_rq_count);
>
>                 }
>
>             }
>
>         spin_unlock(&sched->job_list_lock);
>
>         }
>
>         see that without sched_job->s_fence, you cannot remove the
>         callback from its hw fence,
>
>         any idea??
>
>         BR Monk
>

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