linux-kernel - [PATCH 2/2] drm: add lockdep assert to drm_is_current_master

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Message-Id: <20210730041515.1430237-3-desmondcheongzx@gmail.com>
Date:   Fri, 30 Jul 2021 12:15:15 +0800
From:   Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>
To:     maarten.lankhorst@...ux.intel.com, mripard@...nel.org,
        tzimmermann@...e.de, airlied@...ux.ie, daniel@...ll.ch,
        peterz@...radead.org, mingo@...hat.com, will@...nel.org,
        longman@...hat.com, boqun.feng@...il.com
Cc:     Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>,
        dri-devel@...ts.freedesktop.org, linux-kernel@...r.kernel.org,
        skhan@...uxfoundation.org, gregkh@...uxfoundation.org,
        linux-kernel-mentees@...ts.linuxfoundation.org
Subject: [PATCH 2/2] 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 it in.

Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@...il.com>
---
 drivers/gpu/drm/drm_auth.c | 6 +++---
 1 file changed, 3 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;
 }
 
-- 
2.25.1