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@xxxxxxxxx>
> >>
> >> 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@xxxxxxx>
> >> ---
> >> 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
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