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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> |
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 |
28 | * the same restrictions. | |
e041c683 AS |
29 | * |
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 | */ |
49 | ||
f02c6968 AM |
50 | typedef int (*notifier_fn_t)(struct notifier_block *nb, |
51 | unsigned long action, void *data); | |
52 | ||
e041c683 | 53 | struct notifier_block { |
f02c6968 | 54 | notifier_fn_t notifier_call; |
374a8e0d | 55 | struct notifier_block __rcu *next; |
1da177e4 LT |
56 | int priority; |
57 | }; | |
58 | ||
e041c683 AS |
59 | struct atomic_notifier_head { |
60 | spinlock_t lock; | |
374a8e0d | 61 | struct notifier_block __rcu *head; |
e041c683 AS |
62 | }; |
63 | ||
64 | struct blocking_notifier_head { | |
65 | struct rw_semaphore rwsem; | |
374a8e0d | 66 | struct notifier_block __rcu *head; |
e041c683 AS |
67 | }; |
68 | ||
69 | struct raw_notifier_head { | |
374a8e0d | 70 | struct notifier_block __rcu *head; |
e041c683 AS |
71 | }; |
72 | ||
eabc0694 AS |
73 | struct srcu_notifier_head { |
74 | struct mutex mutex; | |
75 | struct srcu_struct srcu; | |
374a8e0d | 76 | struct notifier_block __rcu *head; |
eabc0694 AS |
77 | }; |
78 | ||
e041c683 AS |
79 | #define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \ |
80 | spin_lock_init(&(name)->lock); \ | |
81 | (name)->head = NULL; \ | |
82 | } while (0) | |
83 | #define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \ | |
84 | init_rwsem(&(name)->rwsem); \ | |
85 | (name)->head = NULL; \ | |
86 | } while (0) | |
87 | #define RAW_INIT_NOTIFIER_HEAD(name) do { \ | |
88 | (name)->head = NULL; \ | |
89 | } while (0) | |
90 | ||
eabc0694 AS |
91 | /* srcu_notifier_heads must be initialized and cleaned up dynamically */ |
92 | extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); | |
93 | #define srcu_cleanup_notifier_head(name) \ | |
94 | cleanup_srcu_struct(&(name)->srcu); | |
95 | ||
e041c683 | 96 | #define ATOMIC_NOTIFIER_INIT(name) { \ |
e4d91918 | 97 | .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ |
e041c683 AS |
98 | .head = NULL } |
99 | #define BLOCKING_NOTIFIER_INIT(name) { \ | |
100 | .rwsem = __RWSEM_INITIALIZER((name).rwsem), \ | |
101 | .head = NULL } | |
102 | #define RAW_NOTIFIER_INIT(name) { \ | |
103 | .head = NULL } | |
eabc0694 | 104 | /* srcu_notifier_heads cannot be initialized statically */ |
e041c683 AS |
105 | |
106 | #define ATOMIC_NOTIFIER_HEAD(name) \ | |
107 | struct atomic_notifier_head name = \ | |
108 | ATOMIC_NOTIFIER_INIT(name) | |
109 | #define BLOCKING_NOTIFIER_HEAD(name) \ | |
110 | struct blocking_notifier_head name = \ | |
111 | BLOCKING_NOTIFIER_INIT(name) | |
112 | #define RAW_NOTIFIER_HEAD(name) \ | |
113 | struct raw_notifier_head name = \ | |
114 | RAW_NOTIFIER_INIT(name) | |
1da177e4 LT |
115 | |
116 | #ifdef __KERNEL__ | |
117 | ||
6f7cc11a GS |
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); | |
124 | extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, | |
125 | struct notifier_block *nb); | |
126 | ||
6546bc42 ND |
127 | extern int blocking_notifier_chain_cond_register( |
128 | struct blocking_notifier_head *nh, | |
129 | struct notifier_block *nb); | |
130 | ||
6f7cc11a GS |
131 | extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, |
132 | struct notifier_block *nb); | |
133 | extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, | |
134 | struct notifier_block *nb); | |
135 | extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, | |
136 | struct notifier_block *nb); | |
137 | extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, | |
138 | struct notifier_block *nb); | |
139 | ||
140 | extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, | |
e041c683 | 141 | unsigned long val, void *v); |
6f7cc11a GS |
142 | extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh, |
143 | unsigned long val, void *v, int nr_to_call, int *nr_calls); | |
144 | extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, | |
e041c683 | 145 | unsigned long val, void *v); |
6f7cc11a GS |
146 | extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh, |
147 | unsigned long val, void *v, int nr_to_call, int *nr_calls); | |
148 | extern int raw_notifier_call_chain(struct raw_notifier_head *nh, | |
e041c683 | 149 | unsigned long val, void *v); |
6f7cc11a GS |
150 | extern int __raw_notifier_call_chain(struct raw_notifier_head *nh, |
151 | unsigned long val, void *v, int nr_to_call, int *nr_calls); | |
152 | extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, | |
eabc0694 | 153 | unsigned long val, void *v); |
6f7cc11a GS |
154 | extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh, |
155 | unsigned long val, void *v, int nr_to_call, int *nr_calls); | |
1da177e4 LT |
156 | |
157 | #define NOTIFY_DONE 0x0000 /* Don't care */ | |
158 | #define NOTIFY_OK 0x0001 /* Suits me */ | |
159 | #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ | |
e041c683 AS |
160 | #define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) |
161 | /* Bad/Veto action */ | |
1da177e4 LT |
162 | /* |
163 | * Clean way to return from the notifier and stop further calls. | |
164 | */ | |
165 | #define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK) | |
166 | ||
fcc5a03a HX |
167 | /* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */ |
168 | static inline int notifier_from_errno(int err) | |
169 | { | |
b957e043 AM |
170 | if (err) |
171 | return NOTIFY_STOP_MASK | (NOTIFY_OK - err); | |
172 | ||
173 | return NOTIFY_OK; | |
fcc5a03a HX |
174 | } |
175 | ||
176 | /* Restore (negative) errno value from notify return value. */ | |
177 | static inline int notifier_to_errno(int ret) | |
178 | { | |
179 | ret &= ~NOTIFY_STOP_MASK; | |
180 | return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0; | |
181 | } | |
182 | ||
1da177e4 LT |
183 | /* |
184 | * Declared notifiers so far. I can imagine quite a few more chains | |
185 | * over time (eg laptop power reset chains, reboot chain (to clean | |
186 | * device units up), device [un]mount chain, module load/unload chain, | |
187 | * low memory chain, screenblank chain (for plug in modular screenblankers) | |
188 | * VC switch chains (for loadable kernel svgalib VC switch helpers) etc... | |
189 | */ | |
190 | ||
80f1ff97 AW |
191 | /* CPU notfiers are defined in include/linux/cpu.h. */ |
192 | ||
dcfe1421 | 193 | /* netdevice notifiers are defined in include/linux/netdevice.h */ |
1da177e4 | 194 | |
c5f41752 | 195 | /* reboot notifiers are defined in include/linux/reboot.h. */ |
1da177e4 | 196 | |
35eb6db1 | 197 | /* Hibernation and suspend events are defined in include/linux/suspend.h. */ |
1da177e4 | 198 | |
a376d3d6 AW |
199 | /* Virtual Terminal events are defined in include/linux/vt.h. */ |
200 | ||
35eb6db1 | 201 | #define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ |
b10d9117 | 202 | |
41ab4396 ST |
203 | /* Console keyboard events. |
204 | * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and | |
205 | * KBD_KEYSYM. */ | |
206 | #define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */ | |
207 | #define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */ | |
208 | #define KBD_UNICODE 0x0003 /* Keyboard unicode */ | |
209 | #define KBD_KEYSYM 0x0004 /* Keyboard keysym */ | |
210 | #define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */ | |
211 | ||
fe9d4f57 AD |
212 | extern struct blocking_notifier_head reboot_notifier_list; |
213 | ||
1da177e4 LT |
214 | #endif /* __KERNEL__ */ |
215 | #endif /* _LINUX_NOTIFIER_H */ |