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SubjectRe: [PATCH v2] drm: Don't free jobs in wait_event_interruptible()
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On 26/09/2019 10:54, Steven Price wrote:
> 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@arm.com>
> ---
>
> Changes from v1:
> * Move list_first_entry_or_null() within the lock

Or rather that was my intention - but apparently I fat fingered and
didn't actually include this change. Sorry - v3 on it's way!

Steve

>
> drivers/gpu/drm/scheduler/sched_main.c | 44 ++++++++++++++------------
> 1 file changed, 24 insertions(+), 20 deletions(-)
>
> diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
> index 9a0ee74d82dc..0ed4aaa4e6d1 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;
> 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;
> -
> -
> - while (!list_empty(&sched->ring_mirror_list)) {
> - struct drm_sched_job *job;
> + return NULL;
>
> - 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);
> + 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 +696,18 @@ 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) {
> + sched->ops->free_job(cleanup_job);
> + cleanup_job = drm_sched_get_cleanup_job(sched);
> + }
>
> if (!entity)
> continue;
>

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