hollalinux
/
linux-sg2042
mirror of https://github.com/sophgo/linux-riscv.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

drm: Fix race between drm_vblank_off() and drm_queue_vblank_event() 

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.

Reviewed-by: Matt Roper <matthew.d.roper@intel.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
This commit is contained in:
Ville Syrjälä 2014-08-06 14:49:52 +03:00 committed by Daniel Vetter
parent 56cc279b29
commit ffe7c73a8d
1 changed files with 13 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

13
drivers/gpu/drm/drm_irq.c
View File

@ -1270,6 +1270,7 @@ 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;
@ -1293,6 +1294,18 @@ 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;