From: Ville Syrjälä ville.syrjala@linux.intel.com
Currently it's possible that the following will happen: 1. drm_wait_vblank() calls drm_vblank_get() 2. drm_vblank_off() gets called 3. drm_wait_vblank() calls drm_queue_vblank_event() which adds the event to the queue event though vblank interrupts are currently disabled (and may not be re-enabled ever again).
To fix the problem, add another vblank->enabled check into drm_queue_vblank_event().
drm_vblank_off() holds event_lock around the vblank disable, so no further locking needs to be added to drm_queue_vblank_event(). vblank disable from another source is not possible since drm_wait_vblank() already holds a vblank reference.
Signed-off-by: Ville Syrjälä ville.syrjala@linux.intel.com --- drivers/gpu/drm/drm_irq.c | 13 +++++++++++++ 1 file changed, 13 insertions(+)
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index 2b97059..82a039a 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -1273,6 +1273,7 @@ static int drm_queue_vblank_event(struct drm_device *dev, int pipe, union drm_wait_vblank *vblwait, struct drm_file *file_priv) { + struct drm_vblank_crtc *vblank = &dev->vblank[pipe]; struct drm_pending_vblank_event *e; struct timeval now; unsigned long flags; @@ -1296,6 +1297,18 @@ static int drm_queue_vblank_event(struct drm_device *dev, int pipe,
spin_lock_irqsave(&dev->event_lock, flags);
+ /* + * drm_vblank_off() might have been called after we called + * drm_vblank_get(). drm_vblank_off() holds event_lock + * around the vblank disable, so no need for further locking. + * The reference from drm_vblank_get() protects against + * vblank disable from another source. + */ + if (!vblank->enabled) { + ret = -EINVAL; + goto err_unlock; + } + if (file_priv->event_space < sizeof e->event) { ret = -EBUSY; goto err_unlock;