diff options
| author | Dmitry Osipenko <dmitry.osipenko@collabora.com> | 2022-05-19 14:02:32 +0300 |
|---|---|---|
| committer | Rafael J. Wysocki <rafael.j.wysocki@intel.com> | 2022-05-19 19:25:06 +0200 |
| commit | 13dfd97a341a5cf9d15f415dd469f45e971ef12a (patch) | |
| tree | 956f0adb0fd184cc3fc9ea45e990f47bfccfa56c | |
| parent | 42226c989789d8da4af1de0c31070c96726d990c (diff) | |
notifier: Add atomic_notifier_call_chain_is_empty()
Add atomic_notifier_call_chain_is_empty() that returns true if given
atomic call chain is empty.
The first user of this new notifier API function will be the kernel
power-off core code that will support power-off call chains. The core
code will need to check whether there is a power-off handler registered
at all in order to decide whether to halt machine or power it off.
Reviewed-by: Michał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
| -rw-r--r-- | include/linux/notifier.h | 2 | ||||
| -rw-r--r-- | kernel/notifier.c | 13 |
2 files changed, 15 insertions, 0 deletions
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. |