Commit 649839d7 authored Aug 02, 2021 by Desmond Cheong Zhi Xi Committed by Daniel Vetter Aug 05, 2021

drm: add lockdep assert to drm_is_current_master_locked



In drm_is_current_master_locked, accessing drm_file.master should be
protected by either drm_file.master_lookup_lock or
drm_device.master_mutex. This was previously awkward to assert with
lockdep.

Following patch ("locking/lockdep: Provide lockdep_assert{,_once}()
helpers"), this assertion is now convenient. So we add in the
assertion and explain this lock design in the kerneldoc.

Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
Acked-by: Boqun Feng <boqun.feng@gmail.com>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Link: https://patchwork.freedesktop.org/patch/msgid/20210802105957.77692-3-desmondcheongzx@gmail.com

parent d19c8137

drivers/gpu/drm/drm_auth.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -63,9 +63,9 @@

		static bool drm_is_current_master_locked(struct drm_file *fpriv)
		{
		/* Either drm_device.master_mutex or drm_file.master_lookup_lock
		* should be held here.
		*/
		lockdep_assert_once(lockdep_is_held(&fpriv->master_lookup_lock) \|\|
		lockdep_is_held(&fpriv->minor->dev->master_mutex));

		return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
		}

include/drm/drm_file.h

+4 −0

Original line number	Diff line number	Diff line
		@@ -233,6 +233,10 @@ struct drm_file {
		* this only matches &drm_device.master if the master is the currently
		* active one.
		*
		* To update @master, both &drm_device.master_mutex and
		* @master_lookup_lock need to be held, therefore holding either of
		* them is safe and enough for the read side.
		*
		* When dereferencing this pointer, either hold struct
		* &drm_device.master_mutex for the duration of the pointer's use, or
		* use drm_file_get_master() if struct &drm_device.master_mutex is not