diff options
| author | Ilija Hadzic <ihadzic@research.bell-labs.com> | 2011-10-31 21:11:57 +0400 |
|---|---|---|
| committer | Dave Airlie <airlied@redhat.com> | 2011-11-11 15:16:30 +0400 |
| commit | a6778e9e7fb57603f15344ceb30098a3f6b7caf4 (patch) | |
| tree | 1422443322e6bd119edab9db60dc6ae2e3d3b29f | |
| parent | bfba16582600ab2c75dc39250a2b8f3b2a42da11 (diff) | |
| download | linux-a6778e9e7fb57603f15344ceb30098a3f6b7caf4.tar.xz | |
drm: add some comments to drm_wait_vblank and drm_queue_vblank_event
during the review of the fix for locks problems in drm_wait_vblank,
a couple of false concerns were raised about how the drm_vblank_get
and drm_vblank_put are used in this function; it turned out that the
code is correct and that it cannot be simplified
add a few comments to explain non-obvious flows in the code,
to prevent "false alarms" in the future
v2: incorporate comments received from Daniel Vetter
Signed-off-by: Ilija Hadzic <ihadzic@research.bell-labs.com>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Signed-off-by: Dave Airlie <airlied@redhat.com>
| -rw-r--r-- | drivers/gpu/drm/drm_irq.c | 7 |
1 files changed, 6 insertions, 1 deletions
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index cb3794a00f98..aa3ac0125d90 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -1125,6 +1125,7 @@ static int drm_queue_vblank_event(struct drm_device *dev, int pipe, trace_drm_vblank_event_delivered(current->pid, pipe, vblwait->request.sequence); } else { + /* drm_handle_vblank_events will call drm_vblank_put */ list_add_tail(&e->base.link, &dev->vblank_event_list); vblwait->reply.sequence = vblwait->request.sequence; } @@ -1205,8 +1206,12 @@ int drm_wait_vblank(struct drm_device *dev, void *data, goto done; } - if (flags & _DRM_VBLANK_EVENT) + if (flags & _DRM_VBLANK_EVENT) { + /* must hold on to the vblank ref until the event fires + * drm_vblank_put will be called asynchronously + */ return drm_queue_vblank_event(dev, crtc, vblwait, file_priv); + } if ((flags & _DRM_VBLANK_NEXTONMISS) && (seq - vblwait->request.sequence) <= (1<<23)) { |