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.
7 * Alan Cox <Alan.Cox@linux.org>
10 #ifndef _LINUX_NOTIFIER_H
11 #define _LINUX_NOTIFIER_H
12 #include <linux/errno.h>
13 #include <linux/mutex.h>
14 #include <linux/rwsem.h>
15 //#include <linux/srcu.h>
18 * Notifier chains are of four types:
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.
27 * SRCU notifier chains: A variant of blocking notifier chains, with
28 * the same restrictions.
30 * atomic_notifier_chain_register() may be called from an atomic context,
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.
35 * atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(),
36 * and srcu_notifier_chain_unregister() _must not_ be called from within
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.
50 struct notifier_block;
52 typedef int (*notifier_fn_t)(struct notifier_block *nb,
53 unsigned long action, void *data);
55 struct notifier_block {
56 notifier_fn_t notifier_call;
57 struct notifier_block __rcu *next;
61 struct atomic_notifier_head {
63 struct notifier_block __rcu *head;
66 struct blocking_notifier_head {
67 struct rw_semaphore rwsem;
68 struct notifier_block __rcu *head;
71 struct raw_notifier_head {
72 struct notifier_block __rcu *head;
75 #define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \
76 spin_lock_init(&(name)->lock); \
77 (name)->head = NULL; \
79 #define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \
80 init_rwsem(&(name)->rwsem); \
81 (name)->head = NULL; \
83 #define RAW_INIT_NOTIFIER_HEAD(name) do { \
84 (name)->head = NULL; \
87 #define ATOMIC_NOTIFIER_INIT(name) { \
88 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
90 #define BLOCKING_NOTIFIER_INIT(name) { \
91 .rwsem = __RWSEM_INITIALIZER((name).rwsem), \
93 #define RAW_NOTIFIER_INIT(name) { \
96 #define ATOMIC_NOTIFIER_HEAD(name) \
97 struct atomic_notifier_head name = \
98 ATOMIC_NOTIFIER_INIT(name)
99 #define BLOCKING_NOTIFIER_HEAD(name) \
100 struct blocking_notifier_head name = \
101 BLOCKING_NOTIFIER_INIT(name)
102 #define RAW_NOTIFIER_HEAD(name) \
103 struct raw_notifier_head name = \
104 RAW_NOTIFIER_INIT(name)
106 #define NOTIFY_DONE 0x0000 /* Don't care */
107 #define NOTIFY_OK 0x0001 /* Suits me */
108 #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
109 #define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002)
110 /* Bad/Veto action */
112 * Clean way to return from the notifier and stop further calls.
114 #define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK)
118 extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
119 struct notifier_block *nb);
120 extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
121 struct notifier_block *nb);
122 extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
123 struct notifier_block *nb);
125 extern int blocking_notifier_chain_cond_register(
126 struct blocking_notifier_head *nh,
127 struct notifier_block *nb);
129 extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
130 struct notifier_block *nb);
131 extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
132 struct notifier_block *nb);
133 extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
134 struct notifier_block *nb);
136 extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
137 unsigned long val, void *v);
138 extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
139 unsigned long val, void *v, int nr_to_call, int *nr_calls);
140 extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
141 unsigned long val, void *v);
142 extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
143 unsigned long val, void *v, int nr_to_call, int *nr_calls);
144 extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
145 unsigned long val, void *v);
146 extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
147 unsigned long val, void *v, int nr_to_call, int *nr_calls);
149 /* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */
150 static inline int notifier_from_errno(int err)
153 return NOTIFY_STOP_MASK | (NOTIFY_OK - err);
158 /* Restore (negative) errno value from notify return value. */
159 static inline int notifier_to_errno(int ret)
161 ret &= ~NOTIFY_STOP_MASK;
162 return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;
166 * Declared notifiers so far. I can imagine quite a few more chains
167 * over time (eg laptop power reset chains, reboot chain (to clean
168 * device units up), device [un]mount chain, module load/unload chain,
169 * low memory chain, screenblank chain (for plug in modular screenblankers)
170 * VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
173 /* CPU notfiers are defined in include/linux/cpu.h. */
175 /* netdevice notifiers are defined in include/linux/netdevice.h */
177 /* reboot notifiers are defined in include/linux/reboot.h. */
179 /* Hibernation and suspend events are defined in include/linux/suspend.h. */
181 /* Virtual Terminal events are defined in include/linux/vt.h. */
183 #define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */
185 /* Console keyboard events.
186 * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and
188 #define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */
189 #define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */
190 #define KBD_UNICODE 0x0003 /* Keyboard unicode */
191 #define KBD_KEYSYM 0x0004 /* Keyboard keysym */
192 #define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */
194 extern struct blocking_notifier_head reboot_notifier_list;
196 #endif /* __KERNEL__ */
197 #endif /* _LINUX_NOTIFIER_H */