[PATCH 2/2] drm: get lock before accessing vblank refcount

[Yunxiang Li]

Acquire vbl_lock before accessing vblank refcount in drm_vblank_put,
just like everywhere else that access the refcount.

Signed-off-by: Yunxiang Li <yunxiang...@amd.com>
---
 drivers/gpu/drm/drm_vblank.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
index 159d13b5d97b..77b8c40fc7ba 100644
--- a/drivers/gpu/drm/drm_vblank.c
+++ b/drivers/gpu/drm/drm_vblank.c
@@ -1203,15 +1203,22 @@ EXPORT_SYMBOL(drm_crtc_vblank_get);
 void drm_vblank_put(struct drm_device *dev, unsigned int pipe)
 {
        struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
+       unsigned long irqflags;
+       int ret;
 
        if (drm_WARN_ON(dev, pipe >= dev->num_crtcs))
                return;
 
-       if (drm_WARN_ON(dev, atomic_read(&vblank->refcount) == 0))
+       spin_lock_irqsave(&dev->vbl_lock, irqflags);
+       if (drm_WARN_ON(dev, atomic_read(&vblank->refcount) == 0)) {
+               spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
                return;
+       }
 
        /* Last user schedules interrupt disable */
-       if (atomic_dec_and_test(&vblank->refcount)) {
+       ret = atomic_dec_and_test(&vblank->refcount);
+       spin_unlock_irqrestore(&dev->vbl_lock, irqflags);
+       if (ret) {
                if (drm_vblank_offdelay == 0)
                        return;
                else if (drm_vblank_offdelay < 0)
-- 
2.37.1