[PATCH 5.4 186/434] drm: Dont free jobs in wait_event_interruptible()

Greg Kroah-Hartman
2019-12-29T17:49:03Z

From: Steven Price <steven.price@arm.com>

[ Upstream commit 588b9828f0744ca13555c4a35cd0251ac8ad8ad2 ]

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. Unfortunately some free callbacks (notably 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.

Tested-by: Christian Gmeiner <christian.gmeiner@gmail.com>
Fixes: 5918045c4ed4 ("drm/scheduler: rework job destruction")
Signed-off-by: Steven Price <steven.price@arm.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/337652/
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/gpu/drm/scheduler/sched_main.c | 43 ++++++++++++++------------
1 file changed, 24 insertions(+), 19 deletions(-)

diff --git a/drivers/gpu/drm/scheduler/sched_main.c b/drivers/gpu/drm/scheduler/sched_main.c
index f39b97ed4ade..2af64459b3d7 100644
--- a/drivers/gpu/drm/scheduler/sched_main.c
+++ b/drivers/gpu/drm/scheduler/sched_main.c
@@ -632,43 +632,41 @@ 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;
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;
}

/**
@@ -708,12 +706,19 @@ 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());
+
+ if (cleanup_job) {
+ sched->ops->free_job(cleanup_job);
+ /* queue timeout for next job */
+ drm_sched_start_timeout(sched);
+ }

if (!entity)
continue;
--
2.20.1