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.
48 typedef int (*notifier_fn_t)(struct notifier_block *nb,
49 unsigned long action, void *data);
51 struct notifier_block {
52 notifier_fn_t notifier_call;
53 struct notifier_block __rcu *next;
57 struct atomic_notifier_head {
59 struct notifier_block __rcu *head;
62 struct blocking_notifier_head {
63 struct rw_semaphore rwsem;
64 struct notifier_block __rcu *head;
67 struct raw_notifier_head {
68 struct notifier_block __rcu *head;
71 struct srcu_notifier_head {
73 struct srcu_struct srcu;
74 struct notifier_block __rcu *head;
77 #define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \
78 spin_lock_init(&(name)->lock); \
79 (name)->head = NULL; \
81 #define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \
82 init_rwsem(&(name)->rwsem); \
83 (name)->head = NULL; \
85 #define RAW_INIT_NOTIFIER_HEAD(name) do { \
86 (name)->head = NULL; \
89 /* srcu_notifier_heads must be cleaned up dynamically */
90 extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
91 #define srcu_cleanup_notifier_head(name) \
92 cleanup_srcu_struct(&(name)->srcu);
94 #define ATOMIC_NOTIFIER_INIT(name) { \
95 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
97 #define BLOCKING_NOTIFIER_INIT(name) { \
98 .rwsem = __RWSEM_INITIALIZER((name).rwsem), \
100 #define RAW_NOTIFIER_INIT(name) { \
103 #define SRCU_NOTIFIER_INIT(name, pcpu) \
105 .mutex = __MUTEX_INITIALIZER(name.mutex), \
107 .srcu = __SRCU_STRUCT_INIT(name.srcu, pcpu), \
110 #define ATOMIC_NOTIFIER_HEAD(name) \
111 struct atomic_notifier_head name = \
112 ATOMIC_NOTIFIER_INIT(name)
113 #define BLOCKING_NOTIFIER_HEAD(name) \
114 struct blocking_notifier_head name = \
115 BLOCKING_NOTIFIER_INIT(name)
116 #define RAW_NOTIFIER_HEAD(name) \
117 struct raw_notifier_head name = \
118 RAW_NOTIFIER_INIT(name)
120 #define _SRCU_NOTIFIER_HEAD(name, mod) \
121 static DEFINE_PER_CPU(struct srcu_struct_array, \
122 name##_head_srcu_array); \
123 mod struct srcu_notifier_head name = \
124 SRCU_NOTIFIER_INIT(name, name##_head_srcu_array)
126 #define SRCU_NOTIFIER_HEAD(name) \
127 _SRCU_NOTIFIER_HEAD(name, )
129 #define SRCU_NOTIFIER_HEAD_STATIC(name) \
130 _SRCU_NOTIFIER_HEAD(name, static)
134 extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
135 struct notifier_block *nb);
136 extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
137 struct notifier_block *nb);
138 extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
139 struct notifier_block *nb);
140 extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
141 struct notifier_block *nb);
143 extern int blocking_notifier_chain_cond_register(
144 struct blocking_notifier_head *nh,
145 struct notifier_block *nb);
147 extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
148 struct notifier_block *nb);
149 extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
150 struct notifier_block *nb);
151 extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
152 struct notifier_block *nb);
153 extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
154 struct notifier_block *nb);
156 extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
157 unsigned long val, void *v);
158 extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
159 unsigned long val, void *v, int nr_to_call, int *nr_calls);
160 extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
161 unsigned long val, void *v);
162 extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
163 unsigned long val, void *v, int nr_to_call, int *nr_calls);
164 extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
165 unsigned long val, void *v);
166 extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
167 unsigned long val, void *v, int nr_to_call, int *nr_calls);
168 extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
169 unsigned long val, void *v);
170 extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
171 unsigned long val, void *v, int nr_to_call, int *nr_calls);
173 #define NOTIFY_DONE 0x0000 /* Don't care */
174 #define NOTIFY_OK 0x0001 /* Suits me */
175 #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
176 #define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002)
177 /* Bad/Veto action */
179 * Clean way to return from the notifier and stop further calls.
181 #define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK)
183 /* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */
184 static inline int notifier_from_errno(int err)
187 return NOTIFY_STOP_MASK | (NOTIFY_OK - err);
192 /* Restore (negative) errno value from notify return value. */
193 static inline int notifier_to_errno(int ret)
195 ret &= ~NOTIFY_STOP_MASK;
196 return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;
200 * Declared notifiers so far. I can imagine quite a few more chains
201 * over time (eg laptop power reset chains, reboot chain (to clean
202 * device units up), device [un]mount chain, module load/unload chain,
203 * low memory chain, screenblank chain (for plug in modular screenblankers)
204 * VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
207 /* CPU notfiers are defined in include/linux/cpu.h. */
209 /* netdevice notifiers are defined in include/linux/netdevice.h */
211 /* reboot notifiers are defined in include/linux/reboot.h. */
213 /* Hibernation and suspend events are defined in include/linux/suspend.h. */
215 /* Virtual Terminal events are defined in include/linux/vt.h. */
217 #define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */
219 /* Console keyboard events.
220 * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and
222 #define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */
223 #define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */
224 #define KBD_UNICODE 0x0003 /* Keyboard unicode */
225 #define KBD_KEYSYM 0x0004 /* Keyboard keysym */
226 #define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */
228 extern struct blocking_notifier_head reboot_notifier_list;
230 #endif /* __KERNEL__ */
231 #endif /* _LINUX_NOTIFIER_H */