Re: [PATCH 2/3] drm/scheduler: Don't call wait_event_killable for signaled process.

From: Andrey Grodzovsky
Date: Thu Apr 26 2018 - 08:52:49 EST

On 04/26/2018 08:34 AM, Andrey Grodzovsky wrote:

On 04/25/2018 08:01 PM, Eric W. Biederman wrote:
Andrey Grodzovsky <Andrey.Grodzovsky@xxxxxxx> writes:

On 04/25/2018 01:17 PM, Oleg Nesterov wrote:
On 04/25, Andrey Grodzovsky wrote:
here (drm_sched_entity_fini) is also a bad idea, but we still want to be
able to exit immediately
and not wait for GPU jobs completion when the reason for reaching this code
is because of KILL
signal to the user process who opened the device file.
Can you hook f_op->flush method?
But this one is called for each task releasing a reference to the the file, so
not sure I see how this solves the problem.
The big question is why do you need to wait during the final closing a

The wait can be terminated so the wait does not appear to be simply a
matter of correctness.

Well, as I understand it, it just means that you don't want to abruptly terminate GPU work in progress without a good
reason (such as KILL signal). When we exit we are going to release various resources GPU is still using so we either
wait for it to complete or terminate the remaining jobs.

Looked more into code, some correction, drm_sched_entity_fini means the SW job queue itself is about to die, so we must
either wait for completion or terminate any outstanding jobs that are still in the SW queue. Anything which already in flight in HW
will still complete.