On Sat, Jul 24, 2021 at 07:18:22PM +0800, Desmond Cheong Zhi Xi wrote:
Inside drm_is_current_master, using the outer drm_device.master_mutex to protect reads of drm_file.master makes the function prone to creating lock hierarchy inversions. Instead, we can use the drm_file.master_lookup_lock that sits at the bottom of the lock hierarchy.
Reported-by: Daniel Vetter daniel.vetter@ffwll.ch Signed-off-by: Desmond Cheong Zhi Xi desmondcheongzx@gmail.com Reviewed-by: Daniel Vetter daniel.vetter@ffwll.ch
Applied to drm-misc-next, thanks for your patch. -Daniel
drivers/gpu/drm/drm_auth.c | 9 +++++---- 1 file changed, 5 insertions(+), 4 deletions(-)
diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index f00354bec3fb..9c24b8cc8e36 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c @@ -63,8 +63,9 @@
static bool drm_is_current_master_locked(struct drm_file *fpriv) {
- lockdep_assert_held_once(&fpriv->minor->dev->master_mutex);
- /* Either drm_device.master_mutex or drm_file.master_lookup_lock
* should be held here.*/}
@@ -82,9 +83,9 @@ bool drm_is_current_master(struct drm_file *fpriv) { bool ret;
- mutex_lock(&fpriv->minor->dev->master_mutex);
- spin_lock(&fpriv->master_lookup_lock); ret = drm_is_current_master_locked(fpriv);
- mutex_unlock(&fpriv->minor->dev->master_mutex);
spin_unlock(&fpriv->master_lookup_lock);
return ret;
}
2.25.1