linux-kernel - Re: drm_sched with panfrost crash on T820

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Date:   Thu, 3 Oct 2019 10:34:19 +0200
From:   Neil Armstrong <narmstrong@...libre.com>
To:     "Grodzovsky, Andrey" <Andrey.Grodzovsky@....com>,
        Hillf Danton <hdanton@...a.com>
Cc:     "daniel@...ll.ch" <daniel@...ll.ch>,
        "airlied@...ux.ie" <airlied@...ux.ie>,
        "Koenig, Christian" <Christian.Koenig@....com>,
        Erico Nunes <nunes.erico@...il.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "steven.price@....com" <steven.price@....com>,
        "dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
        Rob Herring <robh@...nel.org>,
        Tomeu Vizoso <tomeu.vizoso@...labora.com>,
        "open list:ARM/Amlogic Meson..." <linux-amlogic@...ts.infradead.org>
Subject: Re: drm_sched with panfrost crash on T820

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

> 
> 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
> 
> 
>>   
>> --
>>