Commit 13dfd97a authored by Dmitry Osipenko's avatar Dmitry Osipenko Committed by Rafael J. Wysocki
Browse files

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: default avatarMichał Mirosław <mirq-linux@rere.qmqm.pl>
Signed-off-by: default avatarDmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
parent 42226c98

include/linux/notifier.h

+2 −0
Original line number Diff line number Diff line
@@ -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 */

kernel/notifier.c

+13 −0
Original line number Diff line number Diff line
@@ -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.