[Intel-gfx] [PATCH 06/10] drm/syncobj: use the timeline point in drm_syncobj_find_fence v3

[Chris Wilson]

Quoting Koenig, Christian (2018-12-13 12:11:10)
> Am 13.12.18 um 12:37 schrieb Chris Wilson:
> > Quoting Chunming Zhou (2018-12-11 10:34:45)
> >> From: Christian König <ckoenig.leichtzumerken at gmail.com>
> >>
> >> Implement finding the right timeline point in drm_syncobj_find_fence.
> >>
> >> v2: return -EINVAL when the point is not submitted yet.
> >> v3: fix reference counting bug, add flags handling as well
> >>
> >> Signed-off-by: Christian König <christian.koenig at amd.com>
> >> ---
> >>   drivers/gpu/drm/drm_syncobj.c | 43 ++++++++++++++++++++++++++++++++---
> >>   1 file changed, 40 insertions(+), 3 deletions(-)
> >>
> >> diff --git a/drivers/gpu/drm/drm_syncobj.c b/drivers/gpu/drm/drm_syncobj.c
> >> index 76ce13dafc4d..d964b348ecba 100644
> >> --- a/drivers/gpu/drm/drm_syncobj.c
> >> +++ b/drivers/gpu/drm/drm_syncobj.c
> >> @@ -231,16 +231,53 @@ int drm_syncobj_find_fence(struct drm_file *file_private,
> >>                             struct dma_fence **fence)
> >>   {
> >>          struct drm_syncobj *syncobj = drm_syncobj_find(file_private, handle);
> >> -       int ret = 0;
> >> +       struct syncobj_wait_entry wait;
> >> +       int ret;
> >>   
> >>          if (!syncobj)
> >>                  return -ENOENT;
> >>   
> >>          *fence = drm_syncobj_fence_get(syncobj);
> >> -       if (!*fence) {
> >> +       drm_syncobj_put(syncobj);
> >> +
> >> +       if (*fence) {
> >> +               ret = dma_fence_chain_find_seqno(fence, point);
> >> +               if (!ret)
> >> +                       return 0;
> >> +               dma_fence_put(*fence);
> >> +       } else {
> >>                  ret = -EINVAL;
> >>          }
> >> -       drm_syncobj_put(syncobj);
> >> +
> >> +       if (!(flags & DRM_SYNCOBJ_WAIT_FLAGS_WAIT_FOR_SUBMIT))
> >> +               return ret;
> >> +
> >> +       memset(&wait, 0, sizeof(wait));
> >> +       wait.task = current;
> >> +       wait.point = point;
> >> +       drm_syncobj_fence_add_wait(syncobj, &wait);
> >> +
> >> +       do {
> >> +               set_current_state(TASK_INTERRUPTIBLE);
> >> +               if (wait.fence) {
> >> +                       ret = 0;
> >> +                       break;
> >> +               }
> >> +
> >> +               if (signal_pending(current)) {
> >> +                       ret = -ERESTARTSYS;
> >> +                       break;
> >> +               }
> >> +
> >> +               schedule();
> >> +       } while (1);
> > I've previously used a dma_fence_proxy so that we could do nonblocking
> > waits on future submits. That would be preferrable (a requirement for
> > our stupid BKL-driven code).
> 
> That is exactly what I would definitely NAK.
> 
> I would rather say we should come up with a wait_multiple_events() macro 
> and completely nuke the custom implementation of this in:
> 1. dma_fence_default_wait and dma_fence_wait_any_timeout
> 2. the radeon fence implementation
> 3. the nouveau fence implementation
> 4. the syncobj code
> 
> Cause all of them do exactly the same. The dma_fence implementation 
> unfortunately came up with a custom event handling mechanism instead of 
> extending the core Linux wait_event() system.

I don't want a blocking wait at all.
-Chris