diff --git a/include/linux/notifier.h b/include/linux/notifier.h index 87069b8459af..95e2440037de 100644 --- a/include/linux/notifier.h +++ b/include/linux/notifier.h @@ -173,6 +173,8 @@ extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, unsigned long val_up, unsigned long val_down, void *v); +extern bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh); + #define NOTIFY_DONE 0x0000 /* Don't care */ #define NOTIFY_OK 0x0001 /* Suits me */ #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ diff --git a/kernel/notifier.c b/kernel/notifier.c index ba005ebf4730..137b902c985b 100644 --- a/kernel/notifier.c +++ b/kernel/notifier.c @@ -204,6 +204,19 @@ int atomic_notifier_call_chain(struct atomic_notifier_head *nh, EXPORT_SYMBOL_GPL(atomic_notifier_call_chain); NOKPROBE_SYMBOL(atomic_notifier_call_chain); +/** + * atomic_notifier_call_chain_is_empty - Check whether notifier chain is empty + * @nh: Pointer to head of the atomic notifier chain + * + * Checks whether notifier chain is empty. + * + * Returns true is notifier chain is empty, false otherwise. + */ +bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh) +{ + return !rcu_access_pointer(nh->head); +} + /* * Blocking notifier chain routines. All access to the chain is * synchronized by an rwsem.