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SubjectRe: drm_sched with panfrost crash on T820
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On 10/3/19 4:34 AM, Neil Armstrong wrote:
> Hi Andrey,
>
> Le 02/10/2019 à 16:40, Grodzovsky, Andrey a écrit :
>> On 9/30/19 10:52 AM, Hillf Danton wrote:
>>> On Mon, 30 Sep 2019 11:17:45 +0200 Neil Armstrong wrote:
>>>> Did a new run from 5.3:
>>>>
>>>> [ 35.971972] Call trace:
>>>> [ 35.974391] drm_sched_increase_karma+0x5c/0xf0
>>>> ffff000010667f38 FFFF000010667F94
>>>> drivers/gpu/drm/scheduler/sched_main.c:335
>>>>
>>>> The crashing line is :
>>>> if (bad->s_fence->scheduled.context ==
>>>> entity->fence_context) {
>>>>
>>>> Doesn't seem related to guilty job.
>>> Bail out if s_fence is no longer fresh.
>>>
>>> --- a/drivers/gpu/drm/scheduler/sched_main.c
>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
>>> @@ -333,6 +333,10 @@ void drm_sched_increase_karma(struct drm
>>>
>>> spin_lock(&rq->lock);
>>> list_for_each_entry_safe(entity, tmp, &rq->entities, list) {
>>> + if (!smp_load_acquire(&bad->s_fence)) {
>>> + spin_unlock(&rq->lock);
>>> + return;
>>> + }
>>> if (bad->s_fence->scheduled.context ==
>>> entity->fence_context) {
>>> if (atomic_read(&bad->karma) >
>>> @@ -543,7 +547,7 @@ EXPORT_SYMBOL(drm_sched_job_init);
>>> void drm_sched_job_cleanup(struct drm_sched_job *job)
>>> {
>>> dma_fence_put(&job->s_fence->finished);
>>> - job->s_fence = NULL;
>>> + smp_store_release(&job->s_fence, 0);
>>> }
>>> EXPORT_SYMBOL(drm_sched_job_cleanup);
> This fixed the problem on the 10 CI runs.
>
> Neil


These are good news but I still fail to see how this fixes the problem -
Hillf, do you mind explaining how you came up with this particular fix -
what was the bug you saw ?

Andrey

>
>> Does this change help the problem ? Note that drm_sched_job_cleanup is
>> called from scheduler thread which is stopped at all times when work_tdr
>> thread is running and anyway the 'bad' job is still in the
>> ring_mirror_list while it's being accessed from
>> drm_sched_increase_karma so I don't think drm_sched_job_cleanup can be
>> called for it BEFORE or while drm_sched_increase_karma is executed.
>>
>> Andrey
>>
>>
>>>
>>> --
>>>
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