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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,
        sumit.semwal@linaro.org, christian.koenig@amd.com, axboe@kernel.dk,
        oleg@redhat.com, tglx@linutronix.de, dvyukov@google.com,
        walter-zh.wu@mediatek.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: [PATCH v3 1/9] drm: move master_lookup_lock into drm_device
Date:   Wed, 18 Aug 2021 15:38:16 +0800
Message-Id: <20210818073824.1560124-2-desmondcheongzx@gmail.com>
In-Reply-To: <20210818073824.1560124-1-desmondcheongzx@gmail.com>
References: <20210818073824.1560124-1-desmondcheongzx@gmail.com>
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The master_lookup_lock spinlock can be useful as an inner lock for
other attributes that are currently protected by
drm_device.master_mutex.

However, since the spinlock belongs to struct drm_file, its use case
is limited to serializing accesses by a single drm_file. Moving this
lock into struct drm_device allows us to use it for structures that
are accessed by multiple drm_files, such as drm_master.magic_map.

Signed-off-by: Desmond Cheong Zhi Xi <desmondcheongzx@gmail.com>
---
 drivers/gpu/drm/drm_auth.c | 18 +++++++++---------
 drivers/gpu/drm/drm_drv.c  |  1 +
 drivers/gpu/drm/drm_file.c |  1 -
 include/drm/drm_device.h   |  3 +++
 include/drm/drm_file.h     | 10 ++++------
 5 files changed, 17 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/drm_auth.c b/drivers/gpu/drm/drm_auth.c
index 60a6b21474b1..8efb58aa7d95 100644
--- a/drivers/gpu/drm/drm_auth.c
+++ b/drivers/gpu/drm/drm_auth.c
@@ -63,7 +63,7 @@
 
 static bool drm_is_current_master_locked(struct drm_file *fpriv)
 {
-	lockdep_assert_once(lockdep_is_held(&fpriv->master_lookup_lock) ||
+	lockdep_assert_once(lockdep_is_held(&fpriv->minor->dev->master_lookup_lock) ||
 			    lockdep_is_held(&fpriv->minor->dev->master_mutex));
 
 	return fpriv->is_master && drm_lease_owner(fpriv->master) == fpriv->minor->dev->master;
@@ -83,9 +83,9 @@ bool drm_is_current_master(struct drm_file *fpriv)
 {
 	bool ret;
 
-	spin_lock(&fpriv->master_lookup_lock);
+	spin_lock(&fpriv->minor->dev->master_lookup_lock);
 	ret = drm_is_current_master_locked(fpriv);
-	spin_unlock(&fpriv->master_lookup_lock);
+	spin_unlock(&fpriv->minor->dev->master_lookup_lock);
 
 	return ret;
 }
@@ -174,9 +174,9 @@ static int drm_new_set_master(struct drm_device *dev, struct drm_file *fpriv)
 	new_master = drm_master_create(dev);
 	if (!new_master)
 		return -ENOMEM;
-	spin_lock(&fpriv->master_lookup_lock);
+	spin_lock(&dev->master_lookup_lock);
 	fpriv->master = new_master;
-	spin_unlock(&fpriv->master_lookup_lock);
+	spin_unlock(&dev->master_lookup_lock);
 
 	fpriv->is_master = 1;
 	fpriv->authenticated = 1;
@@ -338,9 +338,9 @@ int drm_master_open(struct drm_file *file_priv)
 	if (!dev->master) {
 		ret = drm_new_set_master(dev, file_priv);
 	} else {
-		spin_lock(&file_priv->master_lookup_lock);
+		spin_lock(&dev->master_lookup_lock);
 		file_priv->master = drm_master_get(dev->master);
-		spin_unlock(&file_priv->master_lookup_lock);
+		spin_unlock(&dev->master_lookup_lock);
 	}
 	mutex_unlock(&dev->master_mutex);
 
@@ -405,13 +405,13 @@ struct drm_master *drm_file_get_master(struct drm_file *file_priv)
 {
 	struct drm_master *master = NULL;
 
-	spin_lock(&file_priv->master_lookup_lock);
+	spin_lock(&file_priv->minor->dev->master_lookup_lock);
 	if (!file_priv->master)
 		goto unlock;
 	master = drm_master_get(file_priv->master);
 
 unlock:
-	spin_unlock(&file_priv->master_lookup_lock);
+	spin_unlock(&file_priv->minor->dev->master_lookup_lock);
 	return master;
 }
 EXPORT_SYMBOL(drm_file_get_master);
diff --git a/drivers/gpu/drm/drm_drv.c b/drivers/gpu/drm/drm_drv.c
index 7a5097467ba5..218c16f11c80 100644
--- a/drivers/gpu/drm/drm_drv.c
+++ b/drivers/gpu/drm/drm_drv.c
@@ -612,6 +612,7 @@ static int drm_dev_init(struct drm_device *dev,
 	mutex_init(&dev->filelist_mutex);
 	mutex_init(&dev->clientlist_mutex);
 	mutex_init(&dev->master_mutex);
+	spin_lock_init(&dev->master_lookup_lock);
 
 	ret = drmm_add_action(dev, drm_dev_init_release, NULL);
 	if (ret)
diff --git a/drivers/gpu/drm/drm_file.c b/drivers/gpu/drm/drm_file.c
index ed25168619fc..b8679bbaea69 100644
--- a/drivers/gpu/drm/drm_file.c
+++ b/drivers/gpu/drm/drm_file.c
@@ -176,7 +176,6 @@ struct drm_file *drm_file_alloc(struct drm_minor *minor)
 	init_waitqueue_head(&file->event_wait);
 	file->event_space = 4096; /* set aside 4k for event buffer */
 
-	spin_lock_init(&file->master_lookup_lock);
 	mutex_init(&file->event_read_lock);
 
 	if (drm_core_check_feature(dev, DRIVER_GEM))
diff --git a/include/drm/drm_device.h b/include/drm/drm_device.h
index 604b1d1b2d72..506eb2784819 100644
--- a/include/drm/drm_device.h
+++ b/include/drm/drm_device.h
@@ -152,6 +152,9 @@ struct drm_device {
 	 */
 	struct mutex master_mutex;
 
+	/** @master_lookup_lock: Serializes &drm_file.master. */
+	spinlock_t master_lookup_lock;
+
 	/**
 	 * @open_count:
 	 *
diff --git a/include/drm/drm_file.h b/include/drm/drm_file.h
index a3acb7ac3550..0536e9612a46 100644
--- a/include/drm/drm_file.h
+++ b/include/drm/drm_file.h
@@ -227,15 +227,16 @@ struct drm_file {
 	 * @master:
 	 *
 	 * Master this node is currently associated with. Protected by struct
-	 * &drm_device.master_mutex, and serialized by @master_lookup_lock.
+	 * &drm_device.master_mutex, and serialized by
+	 * &drm_device.master_lookup_lock.
 	 *
 	 * Only relevant if drm_is_primary_client() returns true. Note that
 	 * 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.
+	 * &drm_device.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
@@ -248,9 +249,6 @@ struct drm_file {
 	 */
 	struct drm_master *master;
 
-	/** @master_lock: Serializes @master. */
-	spinlock_t master_lookup_lock;
-
 	/** @pid: Process that opened this file. */
 	struct pid *pid;
 
-- 
2.25.1