1 | /* SPDX-License-Identifier: GPL-2.0 */ |
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> |
14 | #include <linux/mutex.h> |
15 | #include <linux/rwsem.h> |
16 | #include <linux/srcu.h> |
17 | |
18 | /* |
19 | * Notifier chains are of four types: |
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. |
28 | * SRCU notifier chains: A variant of blocking notifier chains, with |
29 | * the same restrictions. |
30 | * |
31 | * atomic_notifier_chain_register() may be called from an atomic context, |
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. |
35 | * |
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 |
46 | * often but notifier_blocks will seldom be removed. |
47 | */ |
48 | |
49 | struct notifier_block; |
50 | |
51 | typedef int (*notifier_fn_t)(struct notifier_block *nb, |
52 | unsigned long action, void *data); |
53 | |
54 | struct notifier_block { |
55 | notifier_fn_t notifier_call; |
56 | struct notifier_block __rcu *next; |
57 | int priority; |
58 | }; |
59 | |
60 | struct atomic_notifier_head { |
61 | spinlock_t lock; |
62 | struct notifier_block __rcu *head; |
63 | }; |
64 | |
65 | struct blocking_notifier_head { |
66 | struct rw_semaphore rwsem; |
67 | struct notifier_block __rcu *head; |
68 | }; |
69 | |
70 | struct raw_notifier_head { |
71 | struct notifier_block __rcu *head; |
72 | }; |
73 | |
74 | struct srcu_notifier_head { |
75 | struct mutex mutex; |
76 | struct srcu_struct srcu; |
77 | struct notifier_block __rcu *head; |
78 | }; |
79 | |
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 | |
92 | /* srcu_notifier_heads must be cleaned up dynamically */ |
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 | |
97 | #define ATOMIC_NOTIFIER_INIT(name) { \ |
98 | .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ |
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 } |
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 | } |
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) |
122 | |
123 | #ifdef CONFIG_TREE_SRCU |
124 | #define _SRCU_NOTIFIER_HEAD(name, mod) \ |
125 | static DEFINE_PER_CPU(struct srcu_data, name##_head_srcu_data); \ |
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 | |
142 | #ifdef __KERNEL__ |
143 | |
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_register_unique_prio( |
154 | struct atomic_notifier_head *nh, struct notifier_block *nb); |
155 | extern int blocking_notifier_chain_register_unique_prio( |
156 | struct blocking_notifier_head *nh, struct notifier_block *nb); |
157 | |
158 | extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, |
159 | struct notifier_block *nb); |
160 | extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, |
161 | struct notifier_block *nb); |
162 | extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, |
163 | struct notifier_block *nb); |
164 | extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, |
165 | struct notifier_block *nb); |
166 | |
167 | extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, |
168 | unsigned long val, void *v); |
169 | extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, |
170 | unsigned long val, void *v); |
171 | extern int raw_notifier_call_chain(struct raw_notifier_head *nh, |
172 | unsigned long val, void *v); |
173 | extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, |
174 | unsigned long val, void *v); |
175 | |
176 | extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh, |
177 | unsigned long val_up, unsigned long val_down, void *v); |
178 | extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, |
179 | unsigned long val_up, unsigned long val_down, void *v); |
180 | |
181 | extern bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh); |
182 | |
183 | #define NOTIFY_DONE 0x0000 /* Don't care */ |
184 | #define NOTIFY_OK 0x0001 /* Suits me */ |
185 | #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ |
186 | #define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) |
187 | /* Bad/Veto action */ |
188 | /* |
189 | * Clean way to return from the notifier and stop further calls. |
190 | */ |
191 | #define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK) |
192 | |
193 | /* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */ |
194 | static inline int notifier_from_errno(int err) |
195 | { |
196 | if (err) |
197 | return NOTIFY_STOP_MASK | (NOTIFY_OK - err); |
198 | |
199 | return NOTIFY_OK; |
200 | } |
201 | |
202 | /* Restore (negative) errno value from notify return value. */ |
203 | static inline int notifier_to_errno(int ret) |
204 | { |
205 | ret &= ~NOTIFY_STOP_MASK; |
206 | return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0; |
207 | } |
208 | |
209 | /* |
210 | * Declared notifiers so far. I can imagine quite a few more chains |
211 | * over time (eg laptop power reset chains, reboot chain (to clean |
212 | * device units up), device [un]mount chain, module load/unload chain, |
213 | * low memory chain, screenblank chain (for plug in modular screenblankers) |
214 | * VC switch chains (for loadable kernel svgalib VC switch helpers) etc... |
215 | */ |
216 | |
217 | /* CPU notfiers are defined in include/linux/cpu.h. */ |
218 | |
219 | /* netdevice notifiers are defined in include/linux/netdevice.h */ |
220 | |
221 | /* reboot notifiers are defined in include/linux/reboot.h. */ |
222 | |
223 | /* Hibernation and suspend events are defined in include/linux/suspend.h. */ |
224 | |
225 | /* Virtual Terminal events are defined in include/linux/vt.h. */ |
226 | |
227 | #define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ |
228 | |
229 | /* Console keyboard events. |
230 | * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and |
231 | * KBD_KEYSYM. */ |
232 | #define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */ |
233 | #define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */ |
234 | #define KBD_UNICODE 0x0003 /* Keyboard unicode */ |
235 | #define KBD_KEYSYM 0x0004 /* Keyboard keysym */ |
236 | #define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */ |
237 | |
238 | extern struct blocking_notifier_head reboot_notifier_list; |
239 | |
240 | #endif /* __KERNEL__ */ |
241 | #endif /* _LINUX_NOTIFIER_H */ |
242 | |