| Message ID | 20210802105957.77692-3-desmondcheongzx@gmail.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | locking/lockdep, drm: apply new lockdep assert in drm_auth.c | expand |
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 <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> Both patches pushed to drm-misc-next, thanks. -Daniel > --- > 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 >
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
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> --- drivers/gpu/drm/drm_auth.c | 6 +++--- include/drm/drm_file.h | 4 ++++ 2 files changed, 7 insertions(+), 3 deletions(-)