[PATCH 1/2] drm/amdgpu: change job_list_lock to mutex

[Huang Rui]

On Tue, Jun 28, 2016 at 05:36:39PM +0800, Christian König wrote:
> Am 28.06.2016 um 09:27 schrieb Huang Rui:
> > On Tue, Jun 28, 2016 at 03:04:18PM +0800, Chunming Zhou wrote:
> >> ring_mirror_list is only used kthread context, no need to spinlock.
> >> otherwise deadlock happens when kthread_park.
> >>
> > Yes, in process context, we prefer to use mutex, because it avoids to
> > grab the CPU all the time.
> >
> > Reviewed-by: Huang Rui <ray.huang at amd.com>
> 
> NAK, the patch won't apply because I've changed the irq save spin lock 
> to a normal one quite a while ago. But, I'm not sure if Alex picked up 
> that patch yet.
> 
> You shouldn't use a mutex here when you don't have a reason to do so. 
> Spin locks have less overhead and we won't expect any contention here.
> 

If the CPU core numbers are large, spinlock will grab the cpu and
might cause some potential deaklock or busy waiting. I think it should
be use mutex if it is not in interrupt context. 

Thanks,
Rui