drm: Drop grab fpriv->fbs_lock in drm_fb_release

[firefly-linux-kernel-4.4.55.git] / drivers / gpu / drm / drm_crtc.c

diff --git a/drivers/gpu/drm/drm_crtc.c b/drivers/gpu/drm/drm_crtc.c
index b7021069b078aa71c161bc0c9991a78ceea2d62a..e79c8d3700d838ff87f1095bcb92a773dbe36018 100644 (file)
--- a/drivers/gpu/drm/drm_crtc.c
+++ b/drivers/gpu/drm/drm_crtc.c
@@ -3400,7 +3400,16 @@ void drm_fb_release(struct drm_file *priv)
        struct drm_device *dev = priv->minor->dev;
        struct drm_framebuffer *fb, *tfb;
 
-       mutex_lock(&priv->fbs_lock);
+       /*
+        * When the file gets released that means no one else can access the fb
+        * list any more, so no need to grab fpriv->fbs_lock. And we need to to
+        * avoid upsetting lockdep since the universal cursor code adds a
+        * framebuffer while holding mutex locks.
+        *
+        * Note that a real deadlock between fpriv->fbs_lock and the modeset
+        * locks is impossible here since no one else but this function can get
+        * at it any more.
+        */
        list_for_each_entry_safe(fb, tfb, &priv->fbs, filp_head) {
 
                mutex_lock(&dev->mode_config.fb_lock);
@@ -3413,7 +3422,6 @@ void drm_fb_release(struct drm_file *priv)
                /* This will also drop the fpriv->fbs reference. */
                drm_framebuffer_remove(fb);
        }
-       mutex_unlock(&priv->fbs_lock);
 }
 
 /**