From: Steven Price <steven.price@arm.com>
To: Tomeu Vizoso <tomeu.vizoso@collabora.com>,
Neil Armstrong <narmstrong@baylibre.com>,
Daniel Vetter <daniel@ffwll.ch>, David Airlie <airlied@linux.ie>,
Rob Herring <robh@kernel.org>
Cc: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/panfrost: Handle resetting on timeout better
Date: Wed, 9 Oct 2019 10:42:29 +0100 [thread overview]
Message-ID: <f31bc3f1-bf51-d406-01a6-8bd29e5518b7@arm.com> (raw)
In-Reply-To: <4fae2d1e-e399-9e2b-60dc-b8a78333845f@collabora.com>
On 07/10/2019 17:14, Tomeu Vizoso wrote:
> On 10/7/19 6:09 AM, Neil Armstrong wrote:
>> Hi Steven,
>>
>> On 07/10/2019 14:50, Steven Price wrote:
>>> Panfrost uses multiple schedulers (one for each slot, so 2 in reality),
>>> and on a timeout has to stop all the schedulers to safely perform a
>>> reset. However more than one scheduler can trigger a timeout at the same
>>> time. This race condition results in jobs being freed while they are
>>> still in use.
>>>
>>> When stopping other slots use cancel_delayed_work_sync() to ensure that
>>> any timeout started for that slot has completed. Also use
>>> mutex_trylock() to obtain reset_lock. This means that only one thread
>>> attempts the reset, the other threads will simply complete without doing
>>> anything (the first thread will wait for this in the call to
>>> cancel_delayed_work_sync()).
>>>
>>> While we're here and since the function is already dependent on
>>> sched_job not being NULL, let's remove the unnecessary checks, along
>>> with a commented out call to panfrost_core_dump() which has never
>>> existed in mainline.
>>>
>>
>> A Fixes: tags would be welcome here so it would be backported to v5.3
>>
>>> Signed-off-by: Steven Price <steven.price@arm.com>
>>> ---
>>> This is a tidied up version of the patch orginally posted here:
>>> http://lkml.kernel.org/r/26ae2a4d-8df1-e8db-3060-41638ed63e2a%40arm.com
>>>
>>> drivers/gpu/drm/panfrost/panfrost_job.c | 17 +++++++++++------
>>> 1 file changed, 11 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/panfrost/panfrost_job.c
>>> b/drivers/gpu/drm/panfrost/panfrost_job.c
>>> index a58551668d9a..dcc9a7603685 100644
>>> --- a/drivers/gpu/drm/panfrost/panfrost_job.c
>>> +++ b/drivers/gpu/drm/panfrost/panfrost_job.c
>>> @@ -381,13 +381,19 @@ static void panfrost_job_timedout(struct
>>> drm_sched_job *sched_job)
>>> job_read(pfdev, JS_TAIL_LO(js)),
>>> sched_job);
>>> - mutex_lock(&pfdev->reset_lock);
>>> + if (!mutex_trylock(&pfdev->reset_lock))
>>> + return;
>>> - for (i = 0; i < NUM_JOB_SLOTS; i++)
>>> - drm_sched_stop(&pfdev->js->queue[i].sched, sched_job);
>>> + for (i = 0; i < NUM_JOB_SLOTS; i++) {
>>> + struct drm_gpu_scheduler *sched = &pfdev->js->queue[i].sched;
>>> +
>>> + drm_sched_stop(sched, sched_job);
>>> + if (js != i)
>>> + /* Ensure any timeouts on other slots have finished */
>>> + cancel_delayed_work_sync(&sched->work_tdr);
>>> + }
>>> - if (sched_job)
>>> - drm_sched_increase_karma(sched_job);
>>> + drm_sched_increase_karma(sched_job);
>>
>> Indeed looks cleaner.
>>
>>> spin_lock_irqsave(&pfdev->js->job_lock, flags);
>>> for (i = 0; i < NUM_JOB_SLOTS; i++) {
>>> @@ -398,7 +404,6 @@ static void panfrost_job_timedout(struct
>>> drm_sched_job *sched_job)
>>> }
>>> spin_unlock_irqrestore(&pfdev->js->job_lock, flags);
>>> - /* panfrost_core_dump(pfdev); */
>>
>> This should be cleaned in another patch !
>
> Seems to me that this should be some kind of TODO, see
> etnaviv_core_dump() for the kind of things we could be doing.
>
> Maybe we can delete this line and mention this in the TODO file?
Fair enough - I'll split this into a separate patch and add an entry to
the TODO file. kbase has a mechanism to "dump on job fault" [1],[2] so
we could do something similar.
Steve
[1]
https://gitlab.freedesktop.org/panfrost/mali_kbase/blob/master/driver/product/kernel/drivers/gpu/arm/midgard/backend/gpu/mali_kbase_debug_job_fault_backend.c
[2]
https://gitlab.freedesktop.org/panfrost/mali_kbase/blob/master/driver/product/kernel/drivers/gpu/arm/midgard/mali_kbase_debug_job_fault.c
> Cheers,
>
> Tomeu
>
>>> panfrost_devfreq_record_transition(pfdev, js);
>>> panfrost_device_reset(pfdev);
>>>
>>
>> Thanks,
>> Testing it right now with the last change removed (doesn't apply on
>> v5.3 with it),
>> results in a few hours... or minutes !
>>
>>
>> Neil
>>
> _______________________________________________
> dri-devel mailing list
> dri-devel@lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/dri-devel
next prev parent reply other threads:[~2019-10-09 9:42 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-10-07 12:50 [PATCH] drm/panfrost: Handle resetting on timeout better Steven Price
2019-10-07 13:09 ` Neil Armstrong
2019-10-07 16:14 ` Tomeu Vizoso
2019-10-09 9:42 ` Steven Price [this message]
2019-10-08 7:48 ` Neil Armstrong
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