Re: [PATCH v3 1/2] drm/sched: Avoid job cleanup if sched thread is parked.

[Andrey Grodzovsky <Andrey.Grodzovsky@amd.com>]

Ping...

Andrey

On 11/26/19 10:36 AM, Andrey Grodzovsky wrote:
>
> On 11/26/19 4:08 AM, Christian König wrote:
>> Am 25.11.19 um 17:51 schrieb Steven Price:
>>> On 25/11/2019 14:10, Andrey Grodzovsky wrote:
>>>> When the sched thread is parked we assume ring_mirror_list is
>>>> not accessed from here.
>>> FWIW I don't think this is necessary. kthread_park() will wait until 
>>> the
>>> thread is parked, at which point the thread is stuck in 
>>> kthread_parkme()
>>> until unparked.
>>>
>>> So all this does is avoid waiting for any cleanup jobs before parking -
>>> which might be a reasonable goal in itself, but if so lets at least
>>> document that.
>>
>> Now that you mention it that is indeed wrong.
>
>
> I wouldn't s call it wrong but superfluous in current code as indeed 
> once the thread is parked there will be no subsequent calls to 
> drm_sched_get_cleanup_job until the thread is unpacked back, if for 
> example we decide to call drm_sched_get_cleanup_job from a work item 
> which keeps scheduled it would be needed.
>
>
>>
>> The real problem is that in the main thread we mangled the call to 
>> kthread_parkme() into drm_sched_blocked() which can be called in 
>> atomic context.
>
>
> Where is the atomic context in wait_event_interruptible ? I seem no to 
> see any.
>
> Andrey
>
>
>>
>> I suggest to rework this so that the kthread_should_park() and 
>> kthread_should_stop() test in wait_event_interruptible() come first 
>> and then call kthread_parkme() outside of the 
>> wait_event_interruptible().
>>
>> Regards,
>> Christian.
>>
>>>
>>> Steve
>>>
>>>> Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@amd.com>
>>>> Reviewed-by: Christian König <christian.koenig@amd.com>
>>>> ---
>>>>   drivers/gpu/drm/scheduler/sched_main.c | 10 +++++++---
>>>>   1 file changed, 7 insertions(+), 3 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c 
>>>> b/drivers/gpu/drm/scheduler/sched_main.c
>>>> index d4cc728..6774955 100644
>>>> --- a/drivers/gpu/drm/scheduler/sched_main.c
>>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
>>>> @@ -635,9 +635,13 @@ drm_sched_get_cleanup_job(struct 
>>>> drm_gpu_scheduler *sched)
>>>>       struct drm_sched_job *job;
>>>>       unsigned long flags;
>>>>   -    /* Don't destroy jobs while the timeout worker is running */
>>>> -    if (sched->timeout != MAX_SCHEDULE_TIMEOUT &&
>>>> -        !cancel_delayed_work(&sched->work_tdr))
>>>> +    /*
>>>> +    * Don't destroy jobs while the timeout worker is running OR 
>>>> thread
>>>> +    * is being parked and hence assumed to not touch ring_mirror_list
>>>> +    */
>>>> +    if ((sched->timeout != MAX_SCHEDULE_TIMEOUT &&
>>>> +         !cancel_delayed_work(&sched->work_tdr)) ||
>>>> +         __kthread_should_park(sched->thread))
>>>>           return NULL;
>>>>         spin_lock_irqsave(&sched->job_list_lock, flags);
>>>>
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>>
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