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

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Date:   Wed, 2 Oct 2019 14:40:13 +0000
From:   "Grodzovsky, Andrey" <Andrey.Grodzovsky@....com>
To:     Hillf Danton <hdanton@...a.com>,
        Neil Armstrong <narmstrong@...libre.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


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);


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


>   
> --
>