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authorIlija Hadzic <ihadzic@research.bell-labs.com>2011-10-31 13:11:57 -0400
committerDave Airlie <airlied@redhat.com>2011-11-11 11:16:30 +0000
commita6778e9e7fb57603f15344ceb30098a3f6b7caf4 (patch)
tree1422443322e6bd119edab9db60dc6ae2e3d3b29f
parentbfba16582600ab2c75dc39250a2b8f3b2a42da11 (diff)
downloadlinux-linaro-stable-a6778e9e7fb57603f15344ceb30098a3f6b7caf4.tar.gz
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.c7
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)) {