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Message-ID: <4ca8b788-57b6-92e9-ab94-a39057320ee2@amd.com>
Date: Fri, 25 Oct 2019 10:34:49 +0000
From: "Koenig, Christian" <Christian.Koenig@....com>
To: Steven Price <steven.price@....com>,
Daniel Vetter <daniel@...ll.ch>,
David Airlie <airlied@...ux.ie>
CC: Sharat Masetty <smasetty@...eaurora.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"dri-devel@...ts.freedesktop.org" <dri-devel@...ts.freedesktop.org>,
"Deucher, Alexander" <Alexander.Deucher@....com>,
Sam Ravnborg <sam@...nborg.org>,
Erico Nunes <nunes.erico@...il.com>
Subject: Re: [RESEND PATCH v4] drm: Don't free jobs in
wait_event_interruptible()
Am 25.10.19 um 12:26 schrieb Steven Price:
> On 25/10/2019 10:49, Koenig, Christian wrote:
>> Am 24.10.19 um 18:24 schrieb Steven Price:
>>> drm_sched_cleanup_jobs() attempts to free finished jobs, however because
>>> it is called as the condition of wait_event_interruptible() it must not
>>> sleep. Unfortuantly some free callbacks (notibly for Panfrost) do sleep.
>>>
>>> Instead let's rename drm_sched_cleanup_jobs() to
>>> drm_sched_get_cleanup_job() and simply return a job for processing if
>>> there is one. The caller can then call the free_job() callback outside
>>> the wait_event_interruptible() where sleeping is possible before
>>> re-checking and returning to sleep if necessary.
>>>
>>> Signed-off-by: Steven Price <steven.price@....com>
>>> ---
>>> Previous posting: https://lore.kernel.org/lkml/20190926141630.14258-1-steven.price@arm.com/
>>>
>>> drivers/gpu/drm/scheduler/sched_main.c | 45 +++++++++++++++-----------
>>> 1 file changed, 26 insertions(+), 19 deletions(-)
>>>
>>> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
>>> index 9a0ee74d82dc..148468447ba9 100644
>>> --- a/drivers/gpu/drm/scheduler/sched_main.c
>>> +++ b/drivers/gpu/drm/scheduler/sched_main.c
>>> @@ -622,43 +622,41 @@ static void drm_sched_process_job(struct dma_fence *f, struct dma_fence_cb *cb)
>>> }
>>>
>>> /**
>>> - * drm_sched_cleanup_jobs - destroy finished jobs
>>> + * drm_sched_get_cleanup_job - fetch the next finished job to be destroyed
>>> *
>>> * @sched: scheduler instance
>>> *
>>> - * Remove all finished jobs from the mirror list and destroy them.
>>> + * Returns the next finished job from the mirror list (if there is one)
>>> + * ready for it to be destroyed.
>>> */
>>> -static void drm_sched_cleanup_jobs(struct drm_gpu_scheduler *sched)
>>> +static struct drm_sched_job *
>>> +drm_sched_get_cleanup_job(struct drm_gpu_scheduler *sched)
>>> {
>>> + struct drm_sched_job *job = NULL;
>> Please don't initialize job here.
> Good spot, will fix.
>
>>> 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))
>>> - return;
>>> -
>>> + return NULL;
>>>
>>> - while (!list_empty(&sched->ring_mirror_list)) {
>>> - struct drm_sched_job *job;
>>> + spin_lock_irqsave(&sched->job_list_lock, flags);
>>>
>>> - job = list_first_entry(&sched->ring_mirror_list,
>>> + job = list_first_entry_or_null(&sched->ring_mirror_list,
>>> struct drm_sched_job, node);
>>> - if (!dma_fence_is_signaled(&job->s_fence->finished))
>>> - break;
>>>
>>> - spin_lock_irqsave(&sched->job_list_lock, flags);
>>> + if (job && dma_fence_is_signaled(&job->s_fence->finished)) {
>>> /* remove job from ring_mirror_list */
>>> list_del_init(&job->node);
>>> - spin_unlock_irqrestore(&sched->job_list_lock, flags);
>>> -
>>> - sched->ops->free_job(job);
>>> + } else {
>>> + job = NULL;
>>> + /* queue timeout for next job */
>>> + drm_sched_start_timeout(sched);
>>> }
>>>
>>> - /* queue timeout for next job */
>>> - spin_lock_irqsave(&sched->job_list_lock, flags);
>>> - drm_sched_start_timeout(sched);
>>> spin_unlock_irqrestore(&sched->job_list_lock, flags);
>>>
>>> + return job;
>>> }
>>>
>>> /**
>>> @@ -698,12 +696,21 @@ static int drm_sched_main(void *param)
>>> struct drm_sched_fence *s_fence;
>>> struct drm_sched_job *sched_job;
>>> struct dma_fence *fence;
>>> + struct drm_sched_job *cleanup_job = NULL;
>>>
>>> wait_event_interruptible(sched->wake_up_worker,
>>> - (drm_sched_cleanup_jobs(sched),
>>> + (cleanup_job = drm_sched_get_cleanup_job(sched)) ||
>>> (!drm_sched_blocked(sched) &&
>>> (entity = drm_sched_select_entity(sched))) ||
>>> - kthread_should_stop()));
>>> + kthread_should_stop());
>>> +
>>> + while (cleanup_job) {
>> Better make this just "if (cleanup_job)"... to make sure that we stop
>> immediately when the thread should stop.
> Ok, no problem. Note that this is a change in behaviour (previously
> drm_sched_cleanup_jobs() was called *before* checking
> kthread_should_stop()). But I can't see the harm.
Yeah, but this is actually a rather nice improvement.
When we say that the thread should stop then that should happen
immediately and not cleanup the jobs first.
Christian.
>
> Steve
>
>> Apart from that looks good to me now,
>> Christian.
>>
>>> + sched->ops->free_job(cleanup_job);
>>> + /* queue timeout for next job */
>>> + drm_sched_start_timeout(sched);
>>> +
>>> + cleanup_job = drm_sched_get_cleanup_job(sched);
>>> + }
>>>
>>> if (!entity)
>>> continue;
>> _______________________________________________
>> dri-devel mailing list
>> dri-devel@...ts.freedesktop.org
>> https://lists.freedesktop.org/mailman/listinfo/dri-devel
>>
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