diff options
| author | Ilija Hadzic <ihadzic@research.bell-labs.com> | 2011-10-31 13:11:57 -0400 |
|---|---|---|
| committer | Eugeni Dodonov <eugeni.dodonov@intel.com> | 2012-02-10 18:01:19 -0200 |
| commit | 2f4854ca89e3eca15a07e82afe78af7b91b68695 (patch) | |
| tree | 79f114399d4da4fa990c11451f5471f502772ab4 | |
| parent | 5e8a764ad43c0c2100658710377601ecafb3fda9 (diff) | |
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>
Signed-off-by: Eugeni Dodonov <eugeni.dodonov@intel.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 ea65ca6f566..a276918f965 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -1105,6 +1105,7 @@ 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; } @@ -1185,8 +1186,12 @@ 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)) { |