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drm: add lockdep assert to drm_is_current_master_locked

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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
This commit is contained in:
Desmond Cheong Zhi Xi 2021-08-02 18:59:57 +08:00 committed by Daniel Vetter
parent d19c813788
commit 649839d7cf
2 changed files with 7 additions and 3 deletions
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6
drivers/gpu/drm/drm_auth.c
View File

@ -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;
}

4
include/drm/drm_file.h
View File

@ -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