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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <94096e4e-0f60-79d1-69b5-c7c3e59a4d78@amd.com>
Date:   Fri, 4 Oct 2019 14:53:31 +0000
From:   "Grodzovsky, Andrey" <Andrey.Grodzovsky@....com>
To:     Neil Armstrong <narmstrong@...libre.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


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