Re: [RESEND PATCH v2 2/2] drm: add lockdep assert to drm_is_current_master_locked
From: Daniel Vetter <hidden>
Date: 2021-08-05 10:08:36
Also in:
dri-devel, intel-gfx, linux-media, lkml
On Mon, Aug 02, 2021 at 06:59:57PM +0800, Desmond Cheong Zhi Xi wrote:
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 <redacted>
Acked-by: Boqun Feng <redacted>
Acked-by: Waiman Long <longman@redhat.com>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>Both patches pushed to drm-misc-next, thanks. -Daniel
quoted hunk ↗ jump to hunk
--- drivers/gpu/drm/drm_auth.c | 6 +++--- include/drm/drm_file.h | 4 ++++ 2 files changed, 7 insertions(+), 3 deletions(-)diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c index 9c24b8cc8e36..6f4d7ff23c80 100644 --- a/drivers/gpu/drm/drm_auth.c +++ b/drivers/gpu/drm/drm_auth.c@@ -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; }diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h index 726cfe0ff5f5..a3acb7ac3550 100644 --- a/include/drm/drm_file.h +++ b/include/drm/drm_file.h@@ -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-- 2.25.1
-- Daniel Vetter Software Engineer, Intel Corporation http://blog.ffwll.ch _______________________________________________ Linux-kernel-mentees mailing list Linux-kernel-mentees@lists.linuxfoundation.org https://lists.linuxfoundation.org/mailman/listinfo/linux-kernel-mentees