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drm/amdgpu: fix incorrect mutex usage v3

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Before this patch the scheduler fence was created when we push the job
into the queue, so we could only get the fence after pushing it.

The mutex now was necessary to prevent the thread pushing the jobs to
the hardware from running faster than the thread pushing the jobs into
the queue.

Otherwise the thread pushing jobs into the queue would have accessed
possible freed up memory when it tries to get a reference to the fence.

So what you get in the end is thread A:
mutex_lock(&job->lock);
...
Kick of thread B.
...
mutex_unlock(&job->lock);

And thread B:
mutex_lock(&job->lock);
....
mutex_unlock(&job->lock);
kfree(job);

I'm actually not sure if I'm still up to date on this, but this usage
pattern used to be not allowed with mutexes. See here as well
https://lwn.net/Articles/575460/.

v2: remove unrelated changes, fix missing owner
v3: rebased, add more commit message

Signed-off-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Christian König
2015-11-05 19:49:48 +01:00
committed by Alex Deucher
parent 4a56228337
commit e284022163
5 changed files with 37 additions and 48 deletions
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10
drivers/gpu/drm/amd/scheduler/gpu_scheduler.c
View File

@@ -276,21 +276,13 @@ static bool amd_sched_entity_in(struct amd_sched_job *sched_job)
*
* Returns 0 for success, negative error code otherwise.
*/
int amd_sched_entity_push_job(struct amd_sched_job *sched_job)
void amd_sched_entity_push_job(struct amd_sched_job *sched_job)
{
struct amd_sched_entity *entity = sched_job->s_entity;
struct amd_sched_fence *fence = amd_sched_fence_create(
entity, sched_job->owner);
if (!fence)
return -ENOMEM;
sched_job->s_fence = fence;
wait_event(entity->sched->job_scheduled,
amd_sched_entity_in(sched_job));
trace_amd_sched_job(sched_job);
return 0;
}
/**