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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> |
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 |
29 | * the same restrictions. | |
e041c683 AS |
30 | * |
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 | |
9c80172b | 46 | * often but notifier_blocks will seldom be removed. |
e041c683 AS |
47 | */ |
48 | ||
27d50c7e TG |
49 | struct notifier_block; |
50 | ||
f02c6968 AM |
51 | typedef int (*notifier_fn_t)(struct notifier_block *nb, |
52 | unsigned long action, void *data); | |
53 | ||
e041c683 | 54 | struct notifier_block { |
f02c6968 | 55 | notifier_fn_t notifier_call; |
374a8e0d | 56 | struct notifier_block __rcu *next; |
1da177e4 LT |
57 | int priority; |
58 | }; | |
59 | ||
e041c683 AS |
60 | struct atomic_notifier_head { |
61 | spinlock_t lock; | |
374a8e0d | 62 | struct notifier_block __rcu *head; |
e041c683 AS |
63 | }; |
64 | ||
65 | struct blocking_notifier_head { | |
66 | struct rw_semaphore rwsem; | |
374a8e0d | 67 | struct notifier_block __rcu *head; |
e041c683 AS |
68 | }; |
69 | ||
70 | struct raw_notifier_head { | |
374a8e0d | 71 | struct notifier_block __rcu *head; |
e041c683 AS |
72 | }; |
73 | ||
eabc0694 AS |
74 | struct srcu_notifier_head { |
75 | struct mutex mutex; | |
76 | struct srcu_struct srcu; | |
374a8e0d | 77 | struct notifier_block __rcu *head; |
eabc0694 AS |
78 | }; |
79 | ||
e041c683 AS |
80 | #define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \ |
81 | spin_lock_init(&(name)->lock); \ | |
82 | (name)->head = NULL; \ | |
83 | } while (0) | |
84 | #define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \ | |
85 | init_rwsem(&(name)->rwsem); \ | |
86 | (name)->head = NULL; \ | |
87 | } while (0) | |
88 | #define RAW_INIT_NOTIFIER_HEAD(name) do { \ | |
89 | (name)->head = NULL; \ | |
90 | } while (0) | |
91 | ||
9c80172b | 92 | /* srcu_notifier_heads must be cleaned up dynamically */ |
eabc0694 AS |
93 | extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); |
94 | #define srcu_cleanup_notifier_head(name) \ | |
95 | cleanup_srcu_struct(&(name)->srcu); | |
96 | ||
e041c683 | 97 | #define ATOMIC_NOTIFIER_INIT(name) { \ |
e4d91918 | 98 | .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ |
e041c683 AS |
99 | .head = NULL } |
100 | #define BLOCKING_NOTIFIER_INIT(name) { \ | |
101 | .rwsem = __RWSEM_INITIALIZER((name).rwsem), \ | |
102 | .head = NULL } | |
103 | #define RAW_NOTIFIER_INIT(name) { \ | |
104 | .head = NULL } | |
9c80172b SAS |
105 | |
106 | #define SRCU_NOTIFIER_INIT(name, pcpu) \ | |
107 | { \ | |
108 | .mutex = __MUTEX_INITIALIZER(name.mutex), \ | |
109 | .head = NULL, \ | |
110 | .srcu = __SRCU_STRUCT_INIT(name.srcu, pcpu), \ | |
111 | } | |
e041c683 AS |
112 | |
113 | #define ATOMIC_NOTIFIER_HEAD(name) \ | |
114 | struct atomic_notifier_head name = \ | |
115 | ATOMIC_NOTIFIER_INIT(name) | |
116 | #define BLOCKING_NOTIFIER_HEAD(name) \ | |
117 | struct blocking_notifier_head name = \ | |
118 | BLOCKING_NOTIFIER_INIT(name) | |
119 | #define RAW_NOTIFIER_HEAD(name) \ | |
120 | struct raw_notifier_head name = \ | |
121 | RAW_NOTIFIER_INIT(name) | |
1da177e4 | 122 | |
9c80172b SAS |
123 | #ifdef CONFIG_TREE_SRCU |
124 | #define _SRCU_NOTIFIER_HEAD(name, mod) \ | |
94e297c5 | 125 | static DEFINE_PER_CPU(struct srcu_data, name##_head_srcu_data); \ |
9c80172b SAS |
126 | mod struct srcu_notifier_head name = \ |
127 | SRCU_NOTIFIER_INIT(name, name##_head_srcu_data) | |
128 | ||
129 | #else | |
130 | #define _SRCU_NOTIFIER_HEAD(name, mod) \ | |
131 | mod struct srcu_notifier_head name = \ | |
132 | SRCU_NOTIFIER_INIT(name, name) | |
133 | ||
134 | #endif | |
135 | ||
136 | #define SRCU_NOTIFIER_HEAD(name) \ | |
137 | _SRCU_NOTIFIER_HEAD(name, /* not static */) | |
138 | ||
139 | #define SRCU_NOTIFIER_HEAD_STATIC(name) \ | |
140 | _SRCU_NOTIFIER_HEAD(name, static) | |
141 | ||
1da177e4 LT |
142 | #ifdef __KERNEL__ |
143 | ||
6f7cc11a GS |
144 | extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh, |
145 | struct notifier_block *nb); | |
146 | extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh, | |
147 | struct notifier_block *nb); | |
148 | extern int raw_notifier_chain_register(struct raw_notifier_head *nh, | |
149 | struct notifier_block *nb); | |
150 | extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, | |
151 | struct notifier_block *nb); | |
152 | ||
153 | extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, | |
154 | struct notifier_block *nb); | |
155 | extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, | |
156 | struct notifier_block *nb); | |
157 | extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, | |
158 | struct notifier_block *nb); | |
159 | extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, | |
160 | struct notifier_block *nb); | |
161 | ||
162 | extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, | |
e041c683 | 163 | unsigned long val, void *v); |
6f7cc11a | 164 | extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, |
e041c683 | 165 | unsigned long val, void *v); |
6f7cc11a | 166 | extern int raw_notifier_call_chain(struct raw_notifier_head *nh, |
e041c683 | 167 | unsigned long val, void *v); |
6f7cc11a | 168 | extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, |
eabc0694 | 169 | unsigned long val, void *v); |
70d93298 PZ |
170 | |
171 | extern int atomic_notifier_call_chain_robust(struct atomic_notifier_head *nh, | |
172 | unsigned long val_up, unsigned long val_down, void *v); | |
173 | extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh, | |
174 | unsigned long val_up, unsigned long val_down, void *v); | |
175 | extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, | |
176 | unsigned long val_up, unsigned long val_down, void *v); | |
1da177e4 LT |
177 | |
178 | #define NOTIFY_DONE 0x0000 /* Don't care */ | |
179 | #define NOTIFY_OK 0x0001 /* Suits me */ | |
180 | #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ | |
e041c683 AS |
181 | #define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) |
182 | /* Bad/Veto action */ | |
1da177e4 LT |
183 | /* |
184 | * Clean way to return from the notifier and stop further calls. | |
185 | */ | |
186 | #define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK) | |
187 | ||
fcc5a03a HX |
188 | /* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */ |
189 | static inline int notifier_from_errno(int err) | |
190 | { | |
b957e043 AM |
191 | if (err) |
192 | return NOTIFY_STOP_MASK | (NOTIFY_OK - err); | |
193 | ||
194 | return NOTIFY_OK; | |
fcc5a03a HX |
195 | } |
196 | ||
197 | /* Restore (negative) errno value from notify return value. */ | |
198 | static inline int notifier_to_errno(int ret) | |
199 | { | |
200 | ret &= ~NOTIFY_STOP_MASK; | |
201 | return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0; | |
202 | } | |
203 | ||
1da177e4 LT |
204 | /* |
205 | * Declared notifiers so far. I can imagine quite a few more chains | |
206 | * over time (eg laptop power reset chains, reboot chain (to clean | |
207 | * device units up), device [un]mount chain, module load/unload chain, | |
208 | * low memory chain, screenblank chain (for plug in modular screenblankers) | |
209 | * VC switch chains (for loadable kernel svgalib VC switch helpers) etc... | |
210 | */ | |
211 | ||
80f1ff97 AW |
212 | /* CPU notfiers are defined in include/linux/cpu.h. */ |
213 | ||
dcfe1421 | 214 | /* netdevice notifiers are defined in include/linux/netdevice.h */ |
1da177e4 | 215 | |
c5f41752 | 216 | /* reboot notifiers are defined in include/linux/reboot.h. */ |
1da177e4 | 217 | |
35eb6db1 | 218 | /* Hibernation and suspend events are defined in include/linux/suspend.h. */ |
1da177e4 | 219 | |
a376d3d6 AW |
220 | /* Virtual Terminal events are defined in include/linux/vt.h. */ |
221 | ||
35eb6db1 | 222 | #define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ |
b10d9117 | 223 | |
41ab4396 ST |
224 | /* Console keyboard events. |
225 | * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and | |
226 | * KBD_KEYSYM. */ | |
227 | #define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */ | |
228 | #define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */ | |
229 | #define KBD_UNICODE 0x0003 /* Keyboard unicode */ | |
230 | #define KBD_KEYSYM 0x0004 /* Keyboard keysym */ | |
231 | #define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */ | |
232 | ||
fe9d4f57 AD |
233 | extern struct blocking_notifier_head reboot_notifier_list; |
234 | ||
1da177e4 LT |
235 | #endif /* __KERNEL__ */ |
236 | #endif /* _LINUX_NOTIFIER_H */ |