regression with d6c650c0a8f6f671e49553725e1db541376d95f2

[Liu, Monk]

Yeah, this one looks good

You can put my reviewed-by on it

From: Koenig, Christian
Sent: 2017年10月13日 18:14
To: Liu, Monk <Monk.Liu at amd.com>; Nicolai Hähnle <nhaehnle at gmail.com>; amd-gfx at lists.freedesktop.org
Subject: Re: regression with d6c650c0a8f6f671e49553725e1db541376d95f2

Good point as well. How about the attached version?

This time we keep an extra reference in amd_sched_process_job() until we are sure that we don't need the s_fence any more.

Regards,
Christian.

Am 13.10.2017 um 11:13 schrieb Liu, Monk:

your patch looks good,  do you think we should also do this:


 void amd_sched_fence_scheduled(struct amd_sched_fence *fence)
 {
-       int ret = fence_signal(&fence->scheduled);
+       int ret;
+
+       fence_get(&fence->scheduled;)
+       ret = fence_signal(&fence->scheduled);

        if (!ret)
                FENCE_TRACE(&fence->scheduled, "signaled from irq context\n");
        else
                FENCE_TRACE(&fence->scheduled, "was already signaled\n");
+       fence_put(&fence->scheduled);
 }




________________________________
From: Koenig, Christian
Sent: Friday, October 13, 2017 5:00:27 PM
To: Liu, Monk; Nicolai Hähnle; amd-gfx at lists.freedesktop.org<mailto:amd-gfx at lists.freedesktop.org>
Subject: Re: regression with d6c650c0a8f6f671e49553725e1db541376d95f2

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><mailto:Christian.Koenig 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

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(struct amd_gpu_scheduler
*sched)

{

    struct amd_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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