[PATCH v2 4/4] drm: hold event_lock while accessing vblank_event_list

[Imre Deak <imre.deak@intel.com>]

Currently the only users of drm_vblank_off() are i915 and gma500,
neither of which holds the event_lock when calling this function.
Fix this by holding the event_lock while traversing the list.

Signed-off-by: Imre Deak <imre.deak@intel.com>
---
 drivers/gpu/drm/drm_irq.c |    3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c
index 3a3d0ce..c6cd558 100644
--- a/drivers/gpu/drm/drm_irq.c
+++ b/drivers/gpu/drm/drm_irq.c
@@ -949,6 +949,8 @@ void drm_vblank_off(struct drm_device *dev, int crtc)
 
 	/* Send any queued vblank events, lest the natives grow disquiet */
 	seq = drm_vblank_count_and_time(dev, crtc, &now);
+
+	spin_lock(&dev->event_lock);
 	list_for_each_entry_safe(e, t, &dev->vblank_event_list, base.link) {
 		if (e->pipe != crtc)
 			continue;
@@ -965,6 +967,7 @@ void drm_vblank_off(struct drm_device *dev, int crtc)
 		trace_drm_vblank_event_delivered(e->base.pid, e->pipe,
 						 e->event.sequence);
 	}
+	spin_unlock(&dev->event_lock);
 
 	spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
 }
-- 
1.7.9.5