Re: [PATCH 3/3] drm/amdgpu: Switch to interrupted wait to recover from ring hang.

[Andrey Grodzovsky]

On 04/24/2018 12:14 PM, Eric W. Biederman wrote:
> Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx> writes:
>
> > If the ring is hanging for some reason allow to recover the waiting
> > by sending fatal signal.
> >
> > Originally-by: David Panariti <David.Panariti@xxxxxxx>
> > Signed-off-by: Andrey Grodzovsky <andrey.grodzovsky@xxxxxxx>
> > ---
> >   drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c | 14 ++++++++++----
> >   1 file changed, 10 insertions(+), 4 deletions(-)
> >
> > diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> > index eb80edf..37a36af 100644
> > --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> > +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ctx.c
> > @@ -421,10 +421,16 @@ int amdgpu_ctx_wait_prev_fence(struct amdgpu_ctx *ctx, unsigned ring_id)
> >   
> >   	if (other) {
> >   		signed long r;
> > -		r = dma_fence_wait_timeout(other, false, MAX_SCHEDULE_TIMEOUT);
> > -		if (r < 0) {
> > -			DRM_ERROR("Error (%ld) waiting for fence!\n", r);
> > -			return r;
> > +
> > +		while (true) {
> > +			if ((r = dma_fence_wait_timeout(other, true,
> > +					MAX_SCHEDULE_TIMEOUT)) >= 0)
> > +				return 0;
> > +
> > +			if (fatal_signal_pending(current)) {
> > +				DRM_ERROR("Error (%ld) waiting for fence!\n", r);
> > +				return r;
> > +			}
> It looks like if you make this code say:
> 			if (fatal_signal_pending(current) ||
> 			    (current->flags & PF_EXITING)) {
> 				DRM_ERROR("Error (%ld) waiting for fence!\n", r);
> 				return r;
> >   		}
> >   	}
> Than you would not need the horrible hack want_signal to deliver signals
> to processes who have passed exit_signal() and don't expect to need
> their signal handling mechanisms anymore.

Let me clarify, the change in want_signal wasn't addressing this code 
but hang in
drm_sched_entity_do_release->wait_event_killable, when you try to 
gracefully terminate by waiting
for all job completions on the GPU pipe you process is using.

Andrey

> Eric