On Mon, Jan 02, 2017 at 02:09:13PM +0200, Laurent Pinchart wrote:
> On Wednesday 08 Jun 2016 17:15:36 Daniel Vetter wrote:
> > +void drm_atomic_helper_commit_cleanup_done(struct drm_atomic_state *state)
> > +{
> > + struct drm_crtc *crtc;
> > + struct drm_crtc_state *crtc_state;
> > + struct drm_crtc_commit *commit;
> > + int i;
> > + long ret;
> > +
> > + for_each_crtc_in_state(state, crtc, crtc_state, i) {
> > + commit = state->crtcs[i].commit;
> > + if (WARN_ON(!commit))
> > + continue;
> > +
> > + spin_lock(&crtc->commit_lock);
> > + complete_all(&commit->cleanup_done);
> > + WARN_ON(!try_wait_for_completion(&commit->hw_done));
> > +
> > + /* commit_list borrows our reference, need to remove before we
> > + * clean up our drm_atomic_state. But only after it actually
> > + * completed, otherwise subsequent commits won't stall
> properly. */
> > + if (try_wait_for_completion(&commit->flip_done)) {
> > + list_del(&commit->commit_entry);
> > + spin_unlock(&crtc->commit_lock);
> > + continue;
> > + }
> > +
> > + spin_unlock(&crtc->commit_lock);
> > +
> > + /* We must wait for the vblank event to signal our completion
> > + * before releasing our reference, since the vblank work does
> > + * not hold a reference of its own. */
> > + ret = wait_for_completion_timeout(&commit->flip_done,
> > + 10*HZ);
>
> Why is this needed ? drm_atomic_helper_commit_cleanup_done() is called in
> commit_tail() after the call to drm_atomic_helper_commit_tail() or to the
> driver's .atomic_commit_tail() handler. If I'm not mistaken both already wait
> for the page flip to complete, either with a call to
> drm_atomic_helper_wait_for_vblanks() in drm_atomic_helper_commit_tail() or
> with a custom method in the driver's .atomic_commit_tail() handler.
You might still race with the event handling, and for legacy cursor
updates we've ommitted the vblank waits. Anyway there's a patch from me on
the m-l to switch over to refcounting, which makes this code here
unecessary. I guess I should apply it to drm-misc.
-Daniel
--
Daniel Vetter
Software Engineer, Intel Corporation
http://blog.ffwll.ch
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