From: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
To: maarten.lankhorst@linux.intel.com, mripard@kernel.org,
tzimmermann@suse.de, airlied@linux.ie, daniel@ffwll.ch,
peterz@infradead.org, mingo@redhat.com, will@kernel.org,
longman@redhat.com, boqun.feng@gmail.com,
sumit.semwal@linaro.org, christian.koenig@amd.com
Cc: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>,
dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org,
intel-gfx@lists.freedesktop.org, linux-media@vger.kernel.org,
linaro-mm-sig@lists.linaro.org, skhan@linuxfoundation.org,
gregkh@linuxfoundation.org,
linux-kernel-mentees@lists.linuxfoundation.org
Subject: [RESEND PATCH v2 2/2] drm: add lockdep assert to drm_is_current_master_locked
Date: Mon, 2 Aug 2021 18:59:57 +0800 [thread overview]
Message-ID: <20210802105957.77692-3-desmondcheongzx@gmail.com> (raw)
In-Reply-To: <20210802105957.77692-1-desmondcheongzx@gmail.com>
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(-)
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
next prev parent reply other threads:[~2021-08-02 11:01 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-08-02 10:59 [RESEND PATCH v2 0/2] locking/lockdep, drm: apply new lockdep assert in drm_auth.c Desmond Cheong Zhi Xi
2021-08-02 10:59 ` [RESEND PATCH v2 1/2] locking/lockdep: Provide lockdep_assert{,_once}() helpers Desmond Cheong Zhi Xi
2021-08-02 10:59 ` Desmond Cheong Zhi Xi [this message]
2021-08-05 10:08 ` [RESEND PATCH v2 2/2] drm: add lockdep assert to drm_is_current_master_locked Daniel Vetter
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