return 0;
}
+static int notifier_chain_cond_register(struct notifier_block **nl,
+ struct notifier_block *n)
+{
+ while ((*nl) != NULL) {
+ if ((*nl) == n)
+ return 0;
+ if (n->priority > (*nl)->priority)
+ break;
+ nl = &((*nl)->next);
+ }
+ n->next = *nl;
+ rcu_assign_pointer(*nl, n);
+ return 0;
+}
+
static int notifier_chain_unregister(struct notifier_block **nl,
struct notifier_block *n)
{
EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);
/**
+ * blocking_notifier_chain_cond_register - Cond 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, only if not already
+ * present in the chain.
+ * Must be called in process context.
+ *
+ * Currently always returns zero.
+ */
+int blocking_notifier_chain_cond_register(struct blocking_notifier_head *nh,
+ struct notifier_block *n)
+{
+ int ret;
+
+ down_write(&nh->rwsem);
+ ret = notifier_chain_cond_register(&nh->head, n);
+ up_write(&nh->rwsem);
+ return ret;
+}
+EXPORT_SYMBOL_GPL(blocking_notifier_chain_cond_register);
+
+/**
* blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
* @nh: Pointer to head of the blocking notifier chain
* @n: Entry to remove from notifier chain