[mirror_ubuntu-zesty-kernel.git] / include / linux / notifier.h

/*
 *	Routines to manage notifier chains for passing status changes to any
 *	interested routines. We need this instead of hard coded call lists so
 *	that modules can poke their nose into the innards. The network devices
 *	needed them so here they are for the rest of you.
 *
 *				Alan Cox <Alan.Cox@linux.org>
 */
 
#ifndef _LINUX_NOTIFIER_H
#define _LINUX_NOTIFIER_H
#include <linux/errno.h>
#include <linux/mutex.h>
#include <linux/rwsem.h>
#include <linux/srcu.h>

/*
 * Notifier chains are of four types:
 *
 *	Atomic notifier chains: Chain callbacks run in interrupt/atomic
 *		context. Callouts are not allowed to block.
 *	Blocking notifier chains: Chain callbacks run in process context.
 *		Callouts are allowed to block.
 *	Raw notifier chains: There are no restrictions on callbacks,
 *		registration, or unregistration.  All locking and protection
 *		must be provided by the caller.
 *	SRCU notifier chains: A variant of blocking notifier chains, with
 *		the same restrictions.
 *
 * atomic_notifier_chain_register() may be called from an atomic context,
 * but blocking_notifier_chain_register() and srcu_notifier_chain_register()
 * must be called from a process context.  Ditto for the corresponding
 * _unregister() routines.
 *
 * atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(),
 * and srcu_notifier_chain_unregister() _must not_ be called from within
 * the call chain.
 *
 * SRCU notifier chains are an alternative form of blocking notifier chains.
 * They use SRCU (Sleepable Read-Copy Update) instead of rw-semaphores for
 * protection of the chain links.  This means there is _very_ low overhead
 * in srcu_notifier_call_chain(): no cache bounces and no memory barriers.
 * As compensation, srcu_notifier_chain_unregister() is rather expensive.
 * SRCU notifier chains should be used when the chain will be called very
 * often but notifier_blocks will seldom be removed.  Also, SRCU notifier
 * chains are slightly more difficult to use because they require special
 * runtime initialization.
 */

struct notifier_block;

typedef	int (*notifier_fn_t)(struct notifier_block *nb,
			unsigned long action, void *data);

struct notifier_block {
	notifier_fn_t notifier_call;
	struct notifier_block __rcu *next;
	int priority;
};

struct atomic_notifier_head {
	spinlock_t lock;
	struct notifier_block __rcu *head;
};

struct blocking_notifier_head {
	struct rw_semaphore rwsem;
	struct notifier_block __rcu *head;
};

struct raw_notifier_head {
	struct notifier_block __rcu *head;
};

struct srcu_notifier_head {
	struct mutex mutex;
	struct srcu_struct srcu;
	struct notifier_block __rcu *head;
};

#define ATOMIC_INIT_NOTIFIER_HEAD(name) do {	\
		spin_lock_init(&(name)->lock);	\
		(name)->head = NULL;		\
	} while (0)
#define BLOCKING_INIT_NOTIFIER_HEAD(name) do {	\
		init_rwsem(&(name)->rwsem);	\
		(name)->head = NULL;		\
	} while (0)
#define RAW_INIT_NOTIFIER_HEAD(name) do {	\
		(name)->head = NULL;		\
	} while (0)

/* srcu_notifier_heads must be initialized and cleaned up dynamically */
extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
#define srcu_cleanup_notifier_head(name)	\
		cleanup_srcu_struct(&(name)->srcu);

#define ATOMIC_NOTIFIER_INIT(name) {				\
		.lock = __SPIN_LOCK_UNLOCKED(name.lock),	\
		.head = NULL }
#define BLOCKING_NOTIFIER_INIT(name) {				\
		.rwsem = __RWSEM_INITIALIZER((name).rwsem),	\
		.head = NULL }
#define RAW_NOTIFIER_INIT(name)	{				\
		.head = NULL }
/* srcu_notifier_heads cannot be initialized statically */

#define ATOMIC_NOTIFIER_HEAD(name)				\
	struct atomic_notifier_head name =			\
		ATOMIC_NOTIFIER_INIT(name)
#define BLOCKING_NOTIFIER_HEAD(name)				\
	struct blocking_notifier_head name =			\
		BLOCKING_NOTIFIER_INIT(name)
#define RAW_NOTIFIER_HEAD(name)					\
	struct raw_notifier_head name =				\
		RAW_NOTIFIER_INIT(name)

#ifdef __KERNEL__

extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
		struct notifier_block *nb);
extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
		struct notifier_block *nb);
extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
		struct notifier_block *nb);
extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
		struct notifier_block *nb);

extern int blocking_notifier_chain_cond_register(
		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,
		struct notifier_block *nb);
extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
		struct notifier_block *nb);
extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
		struct notifier_block *nb);

extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
		unsigned long val, void *v);
extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
	unsigned long val, void *v, int nr_to_call, int *nr_calls);
extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
		unsigned long val, void *v);
extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
	unsigned long val, void *v, int nr_to_call, int *nr_calls);
extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
		unsigned long val, void *v);
extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
	unsigned long val, void *v, int nr_to_call, int *nr_calls);
extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
		unsigned long val, void *v);
extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
	unsigned long val, void *v, int nr_to_call, int *nr_calls);

#define NOTIFY_DONE		0x0000		/* Don't care */
#define NOTIFY_OK		0x0001		/* Suits me */
#define NOTIFY_STOP_MASK	0x8000		/* Don't call further */
#define NOTIFY_BAD		(NOTIFY_STOP_MASK|0x0002)
						/* Bad/Veto action */
/*
 * Clean way to return from the notifier and stop further calls.
 */
#define NOTIFY_STOP		(NOTIFY_OK|NOTIFY_STOP_MASK)

/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */
static inline int notifier_from_errno(int err)
{
	if (err)
		return NOTIFY_STOP_MASK | (NOTIFY_OK - err);

	return NOTIFY_OK;
}

/* Restore (negative) errno value from notify return value. */
static inline int notifier_to_errno(int ret)
{
	ret &= ~NOTIFY_STOP_MASK;
	return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;
}

/*
 *	Declared notifiers so far. I can imagine quite a few more chains
 *	over time (eg laptop power reset chains, reboot chain (to clean 
 *	device units up), device [un]mount chain, module load/unload chain,
 *	low memory chain, screenblank chain (for plug in modular screenblankers) 
 *	VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
 */
 
/* CPU notfiers are defined in include/linux/cpu.h. */

/* netdevice notifiers are defined in include/linux/netdevice.h */

/* reboot notifiers are defined in include/linux/reboot.h. */

/* Hibernation and suspend events are defined in include/linux/suspend.h. */

/* Virtual Terminal events are defined in include/linux/vt.h. */

#define NETLINK_URELEASE	0x0001	/* Unicast netlink socket released */

/* Console keyboard events.
 * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and
 * KBD_KEYSYM. */
#define KBD_KEYCODE		0x0001 /* Keyboard keycode, called before any other */
#define KBD_UNBOUND_KEYCODE	0x0002 /* Keyboard keycode which is not bound to any other */
#define KBD_UNICODE		0x0003 /* Keyboard unicode */
#define KBD_KEYSYM		0x0004 /* Keyboard keysym */
#define KBD_POST_KEYSYM		0x0005 /* Called after keyboard keysym interpretation */

extern struct blocking_notifier_head reboot_notifier_list;

#endif /* __KERNEL__ */
#endif /* _LINUX_NOTIFIER_H */
Commit	Line	Data
1da177e4 LT	1	/*
	2	* Routines to manage notifier chains for passing status changes to any
	3	* interested routines. We need this instead of hard coded call lists so
	4	* that modules can poke their nose into the innards. The network devices
	5	* needed them so here they are for the rest of you.
	6	*
	7	* Alan Cox <Alan.Cox@linux.org>
	8	*/
	9
	10	#ifndef _LINUX_NOTIFIER_H
	11	#define _LINUX_NOTIFIER_H
	12	#include <linux/errno.h>
e041c683 AS	13	#include <linux/mutex.h>
e041c683 AS	14	#include <linux/rwsem.h>
eabc0694	15	#include <linux/srcu.h>
1da177e4	16
e041c683	17	/*
eabc0694	18	* Notifier chains are of four types:
e041c683 AS	19	*
	20	* Atomic notifier chains: Chain callbacks run in interrupt/atomic
	21	* context. Callouts are not allowed to block.
	22	* Blocking notifier chains: Chain callbacks run in process context.
	23	* Callouts are allowed to block.
	24	* Raw notifier chains: There are no restrictions on callbacks,
	25	* registration, or unregistration. All locking and protection
	26	* must be provided by the caller.
eabc0694 AS	27	* SRCU notifier chains: A variant of blocking notifier chains, with
eabc0694 AS	28	* the same restrictions.
e041c683 AS	29	*
e041c683 AS	30	* atomic_notifier_chain_register() may be called from an atomic context,
eabc0694 AS	31	* but blocking_notifier_chain_register() and srcu_notifier_chain_register()
	32	* must be called from a process context. Ditto for the corresponding
	33	* _unregister() routines.
e041c683	34	*
eabc0694 AS	35	* atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(),
	36	* and srcu_notifier_chain_unregister() _must not_ be called from within
	37	* the call chain.
	38	*
	39	* SRCU notifier chains are an alternative form of blocking notifier chains.
	40	* They use SRCU (Sleepable Read-Copy Update) instead of rw-semaphores for
	41	* protection of the chain links. This means there is _very_ low overhead
	42	* in srcu_notifier_call_chain(): no cache bounces and no memory barriers.
	43	* As compensation, srcu_notifier_chain_unregister() is rather expensive.
	44	* SRCU notifier chains should be used when the chain will be called very
	45	* often but notifier_blocks will seldom be removed. Also, SRCU notifier
	46	* chains are slightly more difficult to use because they require special
	47	* runtime initialization.
e041c683 AS	48	*/
e041c683 AS	49
27d50c7e TG	50	struct notifier_block;
27d50c7e TG	51
f02c6968 AM	52	typedef int (notifier_fn_t)(struct notifier_block nb,
	53	unsigned long action, void *data);
	54
e041c683	55	struct notifier_block {
f02c6968	56	notifier_fn_t notifier_call;
374a8e0d	57	struct notifier_block __rcu *next;
1da177e4 LT	58	int priority;
	59	};
	60
e041c683 AS	61	struct atomic_notifier_head {
e041c683 AS	62	spinlock_t lock;
374a8e0d	63	struct notifier_block __rcu *head;
e041c683 AS	64	};
	65
	66	struct blocking_notifier_head {
	67	struct rw_semaphore rwsem;
374a8e0d	68	struct notifier_block __rcu *head;
e041c683 AS	69	};
	70
	71	struct raw_notifier_head {
374a8e0d	72	struct notifier_block __rcu *head;
e041c683 AS	73	};
e041c683 AS	74
eabc0694 AS	75	struct srcu_notifier_head {
	76	struct mutex mutex;
	77	struct srcu_struct srcu;
374a8e0d	78	struct notifier_block __rcu *head;
eabc0694 AS	79	};
eabc0694 AS	80
e041c683 AS	81	#define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \
	82	spin_lock_init(&(name)->lock); \
	83	(name)->head = NULL; \
	84	} while (0)
	85	#define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \
	86	init_rwsem(&(name)->rwsem); \
	87	(name)->head = NULL; \
	88	} while (0)
	89	#define RAW_INIT_NOTIFIER_HEAD(name) do { \
	90	(name)->head = NULL; \
	91	} while (0)
	92
eabc0694 AS	93	/* srcu_notifier_heads must be initialized and cleaned up dynamically */
	94	extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
	95	#define srcu_cleanup_notifier_head(name) \
	96	cleanup_srcu_struct(&(name)->srcu);
	97
e041c683	98	#define ATOMIC_NOTIFIER_INIT(name) { \
e4d91918	99	.lock = __SPIN_LOCK_UNLOCKED(name.lock), \
e041c683 AS	100	.head = NULL }
	101	#define BLOCKING_NOTIFIER_INIT(name) { \
	102	.rwsem = __RWSEM_INITIALIZER((name).rwsem), \
	103	.head = NULL }
	104	#define RAW_NOTIFIER_INIT(name) { \
	105	.head = NULL }
eabc0694	106	/* srcu_notifier_heads cannot be initialized statically */
e041c683 AS	107
	108	#define ATOMIC_NOTIFIER_HEAD(name) \
	109	struct atomic_notifier_head name = \
	110	ATOMIC_NOTIFIER_INIT(name)
	111	#define BLOCKING_NOTIFIER_HEAD(name) \
	112	struct blocking_notifier_head name = \
	113	BLOCKING_NOTIFIER_INIT(name)
	114	#define RAW_NOTIFIER_HEAD(name) \
	115	struct raw_notifier_head name = \
	116	RAW_NOTIFIER_INIT(name)
1da177e4 LT	117
	118	#ifdef __KERNEL__
	119
6f7cc11a GS	120	extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
	121	struct notifier_block *nb);
	122	extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
	123	struct notifier_block *nb);
	124	extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
	125	struct notifier_block *nb);
	126	extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
	127	struct notifier_block *nb);
	128
6546bc42 ND	129	extern int blocking_notifier_chain_cond_register(
	130	struct blocking_notifier_head *nh,
	131	struct notifier_block *nb);
	132
6f7cc11a GS	133	extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
	134	struct notifier_block *nb);
	135	extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
	136	struct notifier_block *nb);
	137	extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
	138	struct notifier_block *nb);
	139	extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
	140	struct notifier_block *nb);
	141
	142	extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
e041c683	143	unsigned long val, void *v);
6f7cc11a GS	144	extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
	145	unsigned long val, void v, int nr_to_call, int nr_calls);
	146	extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
e041c683	147	unsigned long val, void *v);
6f7cc11a GS	148	extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
	149	unsigned long val, void v, int nr_to_call, int nr_calls);
	150	extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
e041c683	151	unsigned long val, void *v);
6f7cc11a GS	152	extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
	153	unsigned long val, void v, int nr_to_call, int nr_calls);
	154	extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
eabc0694	155	unsigned long val, void *v);
6f7cc11a GS	156	extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
6f7cc11a GS	157	unsigned long val, void v, int nr_to_call, int nr_calls);
1da177e4 LT	158
	159	#define NOTIFY_DONE 0x0000 /* Don't care */
	160	#define NOTIFY_OK 0x0001 /* Suits me */
	161	#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
e041c683 AS	162	#define NOTIFY_BAD (NOTIFY_STOP_MASK\|0x0002)
e041c683 AS	163	/* Bad/Veto action */
1da177e4 LT	164	/*
	165	* Clean way to return from the notifier and stop further calls.
	166	*/
	167	#define NOTIFY_STOP (NOTIFY_OK\|NOTIFY_STOP_MASK)
	168
fcc5a03a HX	169	/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */
	170	static inline int notifier_from_errno(int err)
	171	{
b957e043 AM	172	if (err)
	173	return NOTIFY_STOP_MASK \| (NOTIFY_OK - err);
	174
	175	return NOTIFY_OK;
fcc5a03a HX	176	}
	177
	178	/* Restore (negative) errno value from notify return value. */
	179	static inline int notifier_to_errno(int ret)
	180	{
	181	ret &= ~NOTIFY_STOP_MASK;
	182	return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;
	183	}
	184
1da177e4 LT	185	/*
	186	* Declared notifiers so far. I can imagine quite a few more chains
	187	* over time (eg laptop power reset chains, reboot chain (to clean
	188	* device units up), device [un]mount chain, module load/unload chain,
	189	* low memory chain, screenblank chain (for plug in modular screenblankers)
	190	* VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
	191	*/
	192
80f1ff97 AW	193	/* CPU notfiers are defined in include/linux/cpu.h. */
80f1ff97 AW	194
dcfe1421	195	/* netdevice notifiers are defined in include/linux/netdevice.h */
1da177e4	196
c5f41752	197	/* reboot notifiers are defined in include/linux/reboot.h. */
1da177e4	198
35eb6db1	199	/* Hibernation and suspend events are defined in include/linux/suspend.h. */
1da177e4	200
a376d3d6 AW	201	/* Virtual Terminal events are defined in include/linux/vt.h. */
a376d3d6 AW	202
35eb6db1	203	#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */
b10d9117	204
41ab4396 ST	205	/* Console keyboard events.
	206	* Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and
	207	* KBD_KEYSYM. */
	208	#define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */
	209	#define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */
	210	#define KBD_UNICODE 0x0003 /* Keyboard unicode */
	211	#define KBD_KEYSYM 0x0004 /* Keyboard keysym */
	212	#define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */
	213
fe9d4f57 AD	214	extern struct blocking_notifier_head reboot_notifier_list;
fe9d4f57 AD	215
1da177e4 LT	216	#endif /* __KERNEL__ */
1da177e4 LT	217	#endif /* _LINUX_NOTIFIER_H */