Commit c82f898d authored by Dmitry Osipenko's avatar Dmitry Osipenko Committed by Rafael J. Wysocki
Browse files

notifier: Add blocking/atomic_notifier_chain_register_unique_prio() 



Add variant of blocking/atomic_notifier_chain_register() functions that
allow registration of a notifier only if it has unique priority, otherwise
-EBUSY error code is returned by the new functions.

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 13dfd97a

include/linux/notifier.h

+5 −0
Original line number Diff line number Diff line
@@ -150,6 +150,11 @@ extern int raw_notifier_chain_register(struct raw_notifier_head *nh, 
extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,

		struct notifier_block *nb);



extern int atomic_notifier_chain_register_unique_prio(

		struct atomic_notifier_head *nh, struct notifier_block *nb);

extern int blocking_notifier_chain_register_unique_prio(

		struct blocking_notifier_head *nh, struct notifier_block *nb);



extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,

		struct notifier_block *nb);

extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,

kernel/notifier.c

+69 −19
Original line number Diff line number Diff line
@@ -20,7 +20,8 @@ BLOCKING_NOTIFIER_HEAD(reboot_notifier_list); 
 */



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)) {
@@ -30,6 +31,8 @@ static int notifier_chain_register(struct notifier_block **nl, 
		}

		if (n->priority > (*nl)->priority)

			break;

		if (n->priority == (*nl)->priority && unique_priority)

			return -EBUSY;

		nl = &((*nl)->next);

	}

	n->next = *nl;
@@ -144,12 +147,35 @@ int atomic_notifier_chain_register(struct atomic_notifier_head *nh, 
	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
@@ -222,6 +248,26 @@ bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh) 
 *	synchronized by an rwsem.

 */



static int __blocking_notifier_chain_register(struct blocking_notifier_head *nh,

					      struct notifier_block *n,

					      bool unique_priority)

{

	int ret;



	/*

	 * This code gets used during boot-up, when task switching is

	 * not yet working and interrupts must remain disabled.  At

	 * such times we must not call down_write().

	 */

	if (unlikely(system_state == SYSTEM_BOOTING))

		return notifier_chain_register(&nh->head, n, unique_priority);



	down_write(&nh->rwsem);

	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
@@ -235,22 +281,26 @@ bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh) 
int blocking_notifier_chain_register(struct blocking_notifier_head *nh,

		struct notifier_block *n)

{

	int ret;

	return __blocking_notifier_chain_register(nh, n, false);

}

EXPORT_SYMBOL_GPL(blocking_notifier_chain_register);



	/*

	 * This code gets used during boot-up, when task switching is

	 * not yet working and interrupts must remain disabled.  At

	 * such times we must not call down_write().

/**

 *	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.

 */

	if (unlikely(system_state == SYSTEM_BOOTING))

		return notifier_chain_register(&nh->head, n);



	down_write(&nh->rwsem);

	ret = notifier_chain_register(&nh->head, n);

	up_write(&nh->rwsem);

	return ret;

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);

EXPORT_SYMBOL_GPL(blocking_notifier_chain_register_unique_prio);



/**

 *	blocking_notifier_chain_unregister - Remove notifier from a blocking notifier chain
@@ -354,7 +404,7 @@ EXPORT_SYMBOL_GPL(blocking_notifier_call_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);
@@ -433,10 +483,10 @@ int srcu_notifier_chain_register(struct srcu_notifier_head *nh, 
	 * 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;

}