*/
static int notifier_chain_register(struct notifier_block **nl,
- struct notifier_block *n)
+ struct notifier_block *n,
+ bool unique_priority)
{
while ((*nl) != NULL) {
if (unlikely((*nl) == n)) {
}
if (n->priority > (*nl)->priority)
break;
+ if (n->priority == (*nl)->priority && unique_priority)
+ return -EBUSY;
nl = &((*nl)->next);
}
n->next = *nl;
int ret;
spin_lock_irqsave(&nh->lock, flags);
- ret = notifier_chain_register(&nh->head, n);
+ ret = notifier_chain_register(&nh->head, n, false);
spin_unlock_irqrestore(&nh->lock, flags);
return ret;
}
EXPORT_SYMBOL_GPL(atomic_notifier_chain_register);
+/**
+ * atomic_notifier_chain_register_unique_prio - Add notifier to an atomic notifier chain
+ * @nh: Pointer to head of the atomic notifier chain
+ * @n: New entry in notifier chain
+ *
+ * Adds a notifier to an atomic notifier chain if there is no other
+ * notifier registered using the same priority.
+ *
+ * Returns 0 on success, %-EEXIST or %-EBUSY on error.
+ */
+int atomic_notifier_chain_register_unique_prio(struct atomic_notifier_head *nh,
+ struct notifier_block *n)
+{
+ unsigned long flags;
+ int ret;
+
+ spin_lock_irqsave(&nh->lock, flags);
+ ret = notifier_chain_register(&nh->head, n, true);
+ spin_unlock_irqrestore(&nh->lock, flags);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(atomic_notifier_chain_register_unique_prio);
+
/**
* atomic_notifier_chain_unregister - Remove notifier from an atomic notifier chain
* @nh: Pointer to head of the atomic notifier chain
* synchronized by an rwsem.
*/
-/**
- * blocking_notifier_chain_register - Add notifier to a blocking notifier chain
- * @nh: Pointer to head of the blocking notifier chain
- * @n: New entry in notifier chain
- *
- * Adds a notifier to a blocking notifier chain.
- * Must be called in process context.
- *
- * Returns 0 on success, %-EEXIST on error.
- */
-int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
- struct notifier_block *n)
+static int __blocking_notifier_chain_register(struct blocking_notifier_head *nh,
+ struct notifier_block *n,
+ bool unique_priority)
{
int ret;
* such times we must not call down_write().
*/
if (unlikely(system_state == SYSTEM_BOOTING))
- return notifier_chain_register(&nh->head, n);
+ return notifier_chain_register(&nh->head, n, unique_priority);
down_write(&nh->rwsem);
- ret = notifier_chain_register(&nh->head, n);
+ ret = notifier_chain_register(&nh->head, n, unique_priority);
up_write(&nh->rwsem);
return ret;
}
+
+/**
+ * blocking_notifier_chain_register - Add notifier to a blocking notifier chain
+ * @nh: Pointer to head of the blocking notifier chain
+ * @n: New entry in notifier chain
+ *
+ * Adds a notifier to a blocking notifier chain.
+ * Must be called in process context.
+ *
+ * Returns 0 on success, %-EEXIST on error.
+ */
+int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
+ struct notifier_block *n)
+{
+ return __blocking_notifier_chain_register(nh, n, false);
+}
EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
+/**
+ * blocking_notifier_chain_register_unique_prio - Add notifier to a blocking notifier chain
+ * @nh: Pointer to head of the blocking notifier chain
+ * @n: New entry in notifier chain
+ *
+ * Adds a notifier to an blocking notifier chain if there is no other
+ * notifier registered using the same priority.
+ *
+ * Returns 0 on success, %-EEXIST or %-EBUSY on error.
+ */
+int blocking_notifier_chain_register_unique_prio(struct blocking_notifier_head *nh,
+ struct notifier_block *n)
+{
+ return __blocking_notifier_chain_register(nh, n, true);
+}
+EXPORT_SYMBOL_GPL(blocking_notifier_chain_register_unique_prio);
+
/**
* blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
* @nh: Pointer to head of the blocking notifier chain
int raw_notifier_chain_register(struct raw_notifier_head *nh,
struct notifier_block *n)
{
- return notifier_chain_register(&nh->head, n);
+ return notifier_chain_register(&nh->head, n, false);
}
EXPORT_SYMBOL_GPL(raw_notifier_chain_register);
* such times we must not call mutex_lock().
*/
if (unlikely(system_state == SYSTEM_BOOTING))
- return notifier_chain_register(&nh->head, n);
+ return notifier_chain_register(&nh->head, n, false);
mutex_lock(&nh->mutex);
- ret = notifier_chain_register(&nh->head, n);
+ ret = notifier_chain_register(&nh->head, n, false);
mutex_unlock(&nh->mutex);
return ret;
}