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

/* SPDX-License-Identifier: GPL-2.0 */
/*
 *	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
b2441318	1	/* SPDX-License-Identifier: GPL-2.0 */
1da177e4 LT	2	/*
	3	* Routines to manage notifier chains for passing status changes to any
	4	* interested routines. We need this instead of hard coded call lists so
	5	* that modules can poke their nose into the innards. The network devices
	6	* needed them so here they are for the rest of you.
	7	*
	8	* Alan Cox <Alan.Cox@linux.org>
	9	*/
	10
	11	#ifndef _LINUX_NOTIFIER_H
	12	#define _LINUX_NOTIFIER_H
	13	#include <linux/errno.h>
e041c683 AS	14	#include <linux/mutex.h>
e041c683 AS	15	#include <linux/rwsem.h>
eabc0694	16	#include <linux/srcu.h>
1da177e4	17
e041c683	18	/*
eabc0694	19	* Notifier chains are of four types:
e041c683 AS	20	*
	21	* Atomic notifier chains: Chain callbacks run in interrupt/atomic
	22	* context. Callouts are not allowed to block.
	23	* Blocking notifier chains: Chain callbacks run in process context.
	24	* Callouts are allowed to block.
	25	* Raw notifier chains: There are no restrictions on callbacks,
	26	* registration, or unregistration. All locking and protection
	27	* must be provided by the caller.
eabc0694 AS	28	* SRCU notifier chains: A variant of blocking notifier chains, with
eabc0694 AS	29	* the same restrictions.
e041c683 AS	30	*
e041c683 AS	31	* atomic_notifier_chain_register() may be called from an atomic context,
eabc0694 AS	32	* but blocking_notifier_chain_register() and srcu_notifier_chain_register()
	33	* must be called from a process context. Ditto for the corresponding
	34	* _unregister() routines.
e041c683	35	*
eabc0694 AS	36	* atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(),
	37	* and srcu_notifier_chain_unregister() _must not_ be called from within
	38	* the call chain.
	39	*
	40	* SRCU notifier chains are an alternative form of blocking notifier chains.
	41	* They use SRCU (Sleepable Read-Copy Update) instead of rw-semaphores for
	42	* protection of the chain links. This means there is _very_ low overhead
	43	* in srcu_notifier_call_chain(): no cache bounces and no memory barriers.
	44	* As compensation, srcu_notifier_chain_unregister() is rather expensive.
	45	* SRCU notifier chains should be used when the chain will be called very
	46	* often but notifier_blocks will seldom be removed. Also, SRCU notifier
	47	* chains are slightly more difficult to use because they require special
	48	* runtime initialization.
e041c683 AS	49	*/
e041c683 AS	50
27d50c7e TG	51	struct notifier_block;
27d50c7e TG	52
f02c6968 AM	53	typedef int (notifier_fn_t)(struct notifier_block nb,
	54	unsigned long action, void *data);
	55
e041c683	56	struct notifier_block {
f02c6968	57	notifier_fn_t notifier_call;
374a8e0d	58	struct notifier_block __rcu *next;
1da177e4 LT	59	int priority;
	60	};
	61
e041c683 AS	62	struct atomic_notifier_head {
e041c683 AS	63	spinlock_t lock;
374a8e0d	64	struct notifier_block __rcu *head;
e041c683 AS	65	};
	66
	67	struct blocking_notifier_head {
	68	struct rw_semaphore rwsem;
374a8e0d	69	struct notifier_block __rcu *head;
e041c683 AS	70	};
	71
	72	struct raw_notifier_head {
374a8e0d	73	struct notifier_block __rcu *head;
e041c683 AS	74	};
e041c683 AS	75
eabc0694 AS	76	struct srcu_notifier_head {
	77	struct mutex mutex;
	78	struct srcu_struct srcu;
374a8e0d	79	struct notifier_block __rcu *head;
eabc0694 AS	80	};
eabc0694 AS	81
e041c683 AS	82	#define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \
	83	spin_lock_init(&(name)->lock); \
	84	(name)->head = NULL; \
	85	} while (0)
	86	#define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \
	87	init_rwsem(&(name)->rwsem); \
	88	(name)->head = NULL; \
	89	} while (0)
	90	#define RAW_INIT_NOTIFIER_HEAD(name) do { \
	91	(name)->head = NULL; \
	92	} while (0)
	93
eabc0694 AS	94	/* srcu_notifier_heads must be initialized and cleaned up dynamically */
	95	extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
	96	#define srcu_cleanup_notifier_head(name) \
	97	cleanup_srcu_struct(&(name)->srcu);
	98
e041c683	99	#define ATOMIC_NOTIFIER_INIT(name) { \
e4d91918	100	.lock = __SPIN_LOCK_UNLOCKED(name.lock), \
e041c683 AS	101	.head = NULL }
	102	#define BLOCKING_NOTIFIER_INIT(name) { \
	103	.rwsem = __RWSEM_INITIALIZER((name).rwsem), \
	104	.head = NULL }
	105	#define RAW_NOTIFIER_INIT(name) { \
	106	.head = NULL }
eabc0694	107	/* srcu_notifier_heads cannot be initialized statically */
e041c683 AS	108
	109	#define ATOMIC_NOTIFIER_HEAD(name) \
	110	struct atomic_notifier_head name = \
	111	ATOMIC_NOTIFIER_INIT(name)
	112	#define BLOCKING_NOTIFIER_HEAD(name) \
	113	struct blocking_notifier_head name = \
	114	BLOCKING_NOTIFIER_INIT(name)
	115	#define RAW_NOTIFIER_HEAD(name) \
	116	struct raw_notifier_head name = \
	117	RAW_NOTIFIER_INIT(name)
1da177e4 LT	118
	119	#ifdef __KERNEL__
	120
6f7cc11a GS	121	extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
	122	struct notifier_block *nb);
	123	extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
	124	struct notifier_block *nb);
	125	extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
	126	struct notifier_block *nb);
	127	extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
	128	struct notifier_block *nb);
	129
6546bc42 ND	130	extern int blocking_notifier_chain_cond_register(
	131	struct blocking_notifier_head *nh,
	132	struct notifier_block *nb);
	133
6f7cc11a GS	134	extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
	135	struct notifier_block *nb);
	136	extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
	137	struct notifier_block *nb);
	138	extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
	139	struct notifier_block *nb);
	140	extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
	141	struct notifier_block *nb);
	142
	143	extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
e041c683	144	unsigned long val, void *v);
6f7cc11a GS	145	extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
	146	unsigned long val, void v, int nr_to_call, int nr_calls);
	147	extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
e041c683	148	unsigned long val, void *v);
6f7cc11a GS	149	extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
	150	unsigned long val, void v, int nr_to_call, int nr_calls);
	151	extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
e041c683	152	unsigned long val, void *v);
6f7cc11a GS	153	extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
	154	unsigned long val, void v, int nr_to_call, int nr_calls);
	155	extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
eabc0694	156	unsigned long val, void *v);
6f7cc11a GS	157	extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
6f7cc11a GS	158	unsigned long val, void v, int nr_to_call, int nr_calls);
1da177e4 LT	159
	160	#define NOTIFY_DONE 0x0000 /* Don't care */
	161	#define NOTIFY_OK 0x0001 /* Suits me */
	162	#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
e041c683 AS	163	#define NOTIFY_BAD (NOTIFY_STOP_MASK\|0x0002)
e041c683 AS	164	/* Bad/Veto action */
1da177e4 LT	165	/*
	166	* Clean way to return from the notifier and stop further calls.
	167	*/
	168	#define NOTIFY_STOP (NOTIFY_OK\|NOTIFY_STOP_MASK)
	169
fcc5a03a HX	170	/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */
	171	static inline int notifier_from_errno(int err)
	172	{
b957e043 AM	173	if (err)
	174	return NOTIFY_STOP_MASK \| (NOTIFY_OK - err);
	175
	176	return NOTIFY_OK;
fcc5a03a HX	177	}
	178
	179	/* Restore (negative) errno value from notify return value. */
	180	static inline int notifier_to_errno(int ret)
	181	{
	182	ret &= ~NOTIFY_STOP_MASK;
	183	return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;
	184	}
	185
1da177e4 LT	186	/*
	187	* Declared notifiers so far. I can imagine quite a few more chains
	188	* over time (eg laptop power reset chains, reboot chain (to clean
	189	* device units up), device [un]mount chain, module load/unload chain,
	190	* low memory chain, screenblank chain (for plug in modular screenblankers)
	191	* VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
	192	*/
	193
80f1ff97 AW	194	/* CPU notfiers are defined in include/linux/cpu.h. */
80f1ff97 AW	195
dcfe1421	196	/* netdevice notifiers are defined in include/linux/netdevice.h */
1da177e4	197
c5f41752	198	/* reboot notifiers are defined in include/linux/reboot.h. */
1da177e4	199
35eb6db1	200	/* Hibernation and suspend events are defined in include/linux/suspend.h. */
1da177e4	201
a376d3d6 AW	202	/* Virtual Terminal events are defined in include/linux/vt.h. */
a376d3d6 AW	203
35eb6db1	204	#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */
b10d9117	205
41ab4396 ST	206	/* Console keyboard events.
	207	* Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and
	208	* KBD_KEYSYM. */
	209	#define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */
	210	#define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */
	211	#define KBD_UNICODE 0x0003 /* Keyboard unicode */
	212	#define KBD_KEYSYM 0x0004 /* Keyboard keysym */
	213	#define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */
	214
fe9d4f57 AD	215	extern struct blocking_notifier_head reboot_notifier_list;
fe9d4f57 AD	216
1da177e4 LT	217	#endif /* __KERNEL__ */
1da177e4 LT	218	#endif /* _LINUX_NOTIFIER_H */