drm: Introduce blob_lock

Create a new global blob_lock mutex, which protects the blob property
list from insertion and/or deletion.
Signed-off-by: Daniel Stone <daniels@collabora.com>
Reviewed-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>

drivers/gpu/drm/drm_crtc.c

@@ -4216,25 +4216,34 @@ drm_property_create_blob(struct drm_device *dev, size_t length,
 	if (!blob)
 		return NULL;
 
+	blob->length = length;
+
+	memcpy(blob->data, data, length);
+
+	mutex_lock(&dev->mode_config.blob_lock);
+
 	ret = drm_mode_object_get(dev, &blob->base, DRM_MODE_OBJECT_BLOB);
 	if (ret) {
 		kfree(blob);
+		mutex_unlock(&dev->mode_config.blob_lock);
 		return NULL;
 	}
 
-	blob->length = length;
+	list_add_tail(&blob->head, &dev->mode_config.property_blob_list);
 
-	memcpy(blob->data, data, length);
+	mutex_unlock(&dev->mode_config.blob_lock);
 
-	list_add_tail(&blob->head, &dev->mode_config.property_blob_list);
 	return blob;
 }
 
 static void drm_property_destroy_blob(struct drm_device *dev,
 			       struct drm_property_blob *blob)
 {
+	mutex_lock(&dev->mode_config.blob_lock);
 	drm_mode_object_put(dev, &blob->base);
 	list_del(&blob->head);
+	mutex_unlock(&dev->mode_config.blob_lock);
+
 	kfree(blob);
 }
 
@@ -4341,6 +4350,7 @@ int drm_mode_getblob_ioctl(struct drm_device *dev,
 		return -EINVAL;
 
 	drm_modeset_lock_all(dev);
+	mutex_lock(&dev->mode_config.blob_lock);
 	blob = drm_property_blob_find(dev, out_resp->blob_id);
 	if (!blob) {
 		ret = -ENOENT;
@@ -4357,6 +4367,7 @@ int drm_mode_getblob_ioctl(struct drm_device *dev,
 	out_resp->length = blob->length;
 
 done:
+	mutex_unlock(&dev->mode_config.blob_lock);
 	drm_modeset_unlock_all(dev);
 	return ret;
 }
@@ -5490,6 +5501,7 @@ void drm_mode_config_init(struct drm_device *dev)
 	drm_modeset_lock_init(&dev->mode_config.connection_mutex);
 	mutex_init(&dev->mode_config.idr_mutex);
 	mutex_init(&dev->mode_config.fb_lock);
+	mutex_init(&dev->mode_config.blob_lock);
 	INIT_LIST_HEAD(&dev->mode_config.fb_list);
 	INIT_LIST_HEAD(&dev->mode_config.crtc_list);
 	INIT_LIST_HEAD(&dev->mode_config.connector_list);

include/drm/drm_crtc.h

@@ -1048,6 +1048,7 @@ struct drm_mode_group {
  * @poll_running: track polling status for this device
  * @output_poll_work: delayed work for polling in process context
  * @property_blob_list: list of all the blob property objects
+ * @blob_lock: mutex for blob property allocation and management
  * @*_property: core property tracking
  * @preferred_depth: preferred RBG pixel depth, used by fb helpers
  * @prefer_shadow: hint to userspace to prefer shadow-fb rendering
@@ -1103,6 +1104,8 @@ struct drm_mode_config {
 	bool delayed_event;
 	struct delayed_work output_poll_work;
 
+	struct mutex blob_lock;
+
 	/* pointers to standard properties */
 	struct list_head property_blob_list;
 	struct drm_property *edid_property;