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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; | |
95433f72 PM |
76 | #ifdef CONFIG_TREE_SRCU |
77 | struct srcu_usage srcuu; | |
78 | #endif | |
eabc0694 | 79 | struct srcu_struct srcu; |
374a8e0d | 80 | struct notifier_block __rcu *head; |
eabc0694 AS |
81 | }; |
82 | ||
e041c683 AS |
83 | #define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \ |
84 | spin_lock_init(&(name)->lock); \ | |
85 | (name)->head = NULL; \ | |
86 | } while (0) | |
87 | #define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \ | |
88 | init_rwsem(&(name)->rwsem); \ | |
89 | (name)->head = NULL; \ | |
90 | } while (0) | |
91 | #define RAW_INIT_NOTIFIER_HEAD(name) do { \ | |
92 | (name)->head = NULL; \ | |
93 | } while (0) | |
94 | ||
9c80172b | 95 | /* srcu_notifier_heads must be cleaned up dynamically */ |
eabc0694 AS |
96 | extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); |
97 | #define srcu_cleanup_notifier_head(name) \ | |
98 | cleanup_srcu_struct(&(name)->srcu); | |
99 | ||
e041c683 | 100 | #define ATOMIC_NOTIFIER_INIT(name) { \ |
e4d91918 | 101 | .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ |
e041c683 AS |
102 | .head = NULL } |
103 | #define BLOCKING_NOTIFIER_INIT(name) { \ | |
104 | .rwsem = __RWSEM_INITIALIZER((name).rwsem), \ | |
105 | .head = NULL } | |
106 | #define RAW_NOTIFIER_INIT(name) { \ | |
107 | .head = NULL } | |
9c80172b SAS |
108 | |
109 | #define SRCU_NOTIFIER_INIT(name, pcpu) \ | |
110 | { \ | |
111 | .mutex = __MUTEX_INITIALIZER(name.mutex), \ | |
112 | .head = NULL, \ | |
95433f72 | 113 | .srcu = __SRCU_STRUCT_INIT(name.srcu, name.srcuu, pcpu), \ |
9c80172b | 114 | } |
e041c683 AS |
115 | |
116 | #define ATOMIC_NOTIFIER_HEAD(name) \ | |
117 | struct atomic_notifier_head name = \ | |
118 | ATOMIC_NOTIFIER_INIT(name) | |
119 | #define BLOCKING_NOTIFIER_HEAD(name) \ | |
120 | struct blocking_notifier_head name = \ | |
121 | BLOCKING_NOTIFIER_INIT(name) | |
122 | #define RAW_NOTIFIER_HEAD(name) \ | |
123 | struct raw_notifier_head name = \ | |
124 | RAW_NOTIFIER_INIT(name) | |
1da177e4 | 125 | |
9c80172b SAS |
126 | #ifdef CONFIG_TREE_SRCU |
127 | #define _SRCU_NOTIFIER_HEAD(name, mod) \ | |
94e297c5 | 128 | static DEFINE_PER_CPU(struct srcu_data, name##_head_srcu_data); \ |
9c80172b SAS |
129 | mod struct srcu_notifier_head name = \ |
130 | SRCU_NOTIFIER_INIT(name, name##_head_srcu_data) | |
131 | ||
132 | #else | |
133 | #define _SRCU_NOTIFIER_HEAD(name, mod) \ | |
134 | mod struct srcu_notifier_head name = \ | |
135 | SRCU_NOTIFIER_INIT(name, name) | |
136 | ||
137 | #endif | |
138 | ||
139 | #define SRCU_NOTIFIER_HEAD(name) \ | |
140 | _SRCU_NOTIFIER_HEAD(name, /* not static */) | |
141 | ||
142 | #define SRCU_NOTIFIER_HEAD_STATIC(name) \ | |
143 | _SRCU_NOTIFIER_HEAD(name, static) | |
144 | ||
1da177e4 LT |
145 | #ifdef __KERNEL__ |
146 | ||
6f7cc11a GS |
147 | extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh, |
148 | struct notifier_block *nb); | |
149 | extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh, | |
150 | struct notifier_block *nb); | |
151 | extern int raw_notifier_chain_register(struct raw_notifier_head *nh, | |
152 | struct notifier_block *nb); | |
153 | extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, | |
154 | struct notifier_block *nb); | |
155 | ||
c82f898d DO |
156 | extern int atomic_notifier_chain_register_unique_prio( |
157 | struct atomic_notifier_head *nh, struct notifier_block *nb); | |
158 | extern int blocking_notifier_chain_register_unique_prio( | |
159 | struct blocking_notifier_head *nh, struct notifier_block *nb); | |
160 | ||
6f7cc11a GS |
161 | extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, |
162 | struct notifier_block *nb); | |
163 | extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, | |
164 | struct notifier_block *nb); | |
165 | extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, | |
166 | struct notifier_block *nb); | |
167 | extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, | |
168 | struct notifier_block *nb); | |
169 | ||
170 | extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, | |
e041c683 | 171 | unsigned long val, void *v); |
6f7cc11a | 172 | extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, |
e041c683 | 173 | unsigned long val, void *v); |
6f7cc11a | 174 | extern int raw_notifier_call_chain(struct raw_notifier_head *nh, |
e041c683 | 175 | unsigned long val, void *v); |
6f7cc11a | 176 | extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, |
eabc0694 | 177 | unsigned long val, void *v); |
70d93298 | 178 | |
70d93298 PZ |
179 | extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh, |
180 | unsigned long val_up, unsigned long val_down, void *v); | |
181 | extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, | |
182 | unsigned long val_up, unsigned long val_down, void *v); | |
1da177e4 | 183 | |
13dfd97a DO |
184 | extern bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh); |
185 | ||
1da177e4 LT |
186 | #define NOTIFY_DONE 0x0000 /* Don't care */ |
187 | #define NOTIFY_OK 0x0001 /* Suits me */ | |
188 | #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ | |
e041c683 AS |
189 | #define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) |
190 | /* Bad/Veto action */ | |
1da177e4 LT |
191 | /* |
192 | * Clean way to return from the notifier and stop further calls. | |
193 | */ | |
194 | #define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK) | |
195 | ||
fcc5a03a HX |
196 | /* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */ |
197 | static inline int notifier_from_errno(int err) | |
198 | { | |
b957e043 AM |
199 | if (err) |
200 | return NOTIFY_STOP_MASK | (NOTIFY_OK - err); | |
201 | ||
202 | return NOTIFY_OK; | |
fcc5a03a HX |
203 | } |
204 | ||
205 | /* Restore (negative) errno value from notify return value. */ | |
206 | static inline int notifier_to_errno(int ret) | |
207 | { | |
208 | ret &= ~NOTIFY_STOP_MASK; | |
209 | return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0; | |
210 | } | |
211 | ||
1da177e4 LT |
212 | /* |
213 | * Declared notifiers so far. I can imagine quite a few more chains | |
214 | * over time (eg laptop power reset chains, reboot chain (to clean | |
215 | * device units up), device [un]mount chain, module load/unload chain, | |
216 | * low memory chain, screenblank chain (for plug in modular screenblankers) | |
217 | * VC switch chains (for loadable kernel svgalib VC switch helpers) etc... | |
218 | */ | |
219 | ||
80f1ff97 AW |
220 | /* CPU notfiers are defined in include/linux/cpu.h. */ |
221 | ||
dcfe1421 | 222 | /* netdevice notifiers are defined in include/linux/netdevice.h */ |
1da177e4 | 223 | |
c5f41752 | 224 | /* reboot notifiers are defined in include/linux/reboot.h. */ |
1da177e4 | 225 | |
35eb6db1 | 226 | /* Hibernation and suspend events are defined in include/linux/suspend.h. */ |
1da177e4 | 227 | |
a376d3d6 AW |
228 | /* Virtual Terminal events are defined in include/linux/vt.h. */ |
229 | ||
35eb6db1 | 230 | #define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ |
b10d9117 | 231 | |
41ab4396 ST |
232 | /* Console keyboard events. |
233 | * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and | |
234 | * KBD_KEYSYM. */ | |
235 | #define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */ | |
236 | #define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */ | |
237 | #define KBD_UNICODE 0x0003 /* Keyboard unicode */ | |
238 | #define KBD_KEYSYM 0x0004 /* Keyboard keysym */ | |
239 | #define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */ | |
240 | ||
fe9d4f57 AD |
241 | extern struct blocking_notifier_head reboot_notifier_list; |
242 | ||
1da177e4 LT |
243 | #endif /* __KERNEL__ */ |
244 | #endif /* _LINUX_NOTIFIER_H */ |