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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> |
13 | #include <linux/mutex.h> |
14 | #include <linux/rwsem.h> |
15 | #include <linux/srcu.h> |
16 | |
17 | /* |
18 | * Notifier chains are of four types: |
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. |
27 | * SRCU notifier chains: A variant of blocking notifier chains, with |
28 | * the same restrictions. |
29 | * |
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. |
34 | * |
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. |
48 | */ |
49 | |
50 | struct notifier_block { |
51 | int (*notifier_call)(struct notifier_block *, unsigned long, void *); |
52 | struct notifier_block __rcu *next; |
53 | int priority; |
54 | }; |
55 | |
56 | struct atomic_notifier_head { |
57 | spinlock_t lock; |
58 | struct notifier_block __rcu *head; |
59 | }; |
60 | |
61 | struct blocking_notifier_head { |
62 | struct rw_semaphore rwsem; |
63 | struct notifier_block __rcu *head; |
64 | }; |
65 | |
66 | struct raw_notifier_head { |
67 | struct notifier_block __rcu *head; |
68 | }; |
69 | |
70 | struct srcu_notifier_head { |
71 | struct mutex mutex; |
72 | struct srcu_struct srcu; |
73 | struct notifier_block __rcu *head; |
74 | }; |
75 | |
76 | #define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \ |
77 | spin_lock_init(&(name)->lock); \ |
78 | (name)->head = NULL; \ |
79 | } while (0) |
80 | #define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \ |
81 | init_rwsem(&(name)->rwsem); \ |
82 | (name)->head = NULL; \ |
83 | } while (0) |
84 | #define RAW_INIT_NOTIFIER_HEAD(name) do { \ |
85 | (name)->head = NULL; \ |
86 | } while (0) |
87 | |
88 | /* srcu_notifier_heads must be initialized and cleaned up dynamically */ |
89 | extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); |
90 | #define srcu_cleanup_notifier_head(name) \ |
91 | cleanup_srcu_struct(&(name)->srcu); |
92 | |
93 | #define ATOMIC_NOTIFIER_INIT(name) { \ |
94 | .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ |
95 | .head = NULL } |
96 | #define BLOCKING_NOTIFIER_INIT(name) { \ |
97 | .rwsem = __RWSEM_INITIALIZER((name).rwsem), \ |
98 | .head = NULL } |
99 | #define RAW_NOTIFIER_INIT(name) { \ |
100 | .head = NULL } |
101 | /* srcu_notifier_heads cannot be initialized statically */ |
102 | |
103 | #define ATOMIC_NOTIFIER_HEAD(name) \ |
104 | struct atomic_notifier_head name = \ |
105 | ATOMIC_NOTIFIER_INIT(name) |
106 | #define BLOCKING_NOTIFIER_HEAD(name) \ |
107 | struct blocking_notifier_head name = \ |
108 | BLOCKING_NOTIFIER_INIT(name) |
109 | #define RAW_NOTIFIER_HEAD(name) \ |
110 | struct raw_notifier_head name = \ |
111 | RAW_NOTIFIER_INIT(name) |
112 | |
113 | #ifdef __KERNEL__ |
114 | |
115 | extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh, |
116 | struct notifier_block *nb); |
117 | extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh, |
118 | struct notifier_block *nb); |
119 | extern int raw_notifier_chain_register(struct raw_notifier_head *nh, |
120 | struct notifier_block *nb); |
121 | extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, |
122 | struct notifier_block *nb); |
123 | |
124 | extern int blocking_notifier_chain_cond_register( |
125 | struct blocking_notifier_head *nh, |
126 | struct notifier_block *nb); |
127 | |
128 | extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, |
129 | struct notifier_block *nb); |
130 | extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, |
131 | struct notifier_block *nb); |
132 | extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, |
133 | struct notifier_block *nb); |
134 | extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, |
135 | struct notifier_block *nb); |
136 | |
137 | extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, |
138 | unsigned long val, void *v); |
139 | extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh, |
140 | unsigned long val, void *v, int nr_to_call, int *nr_calls); |
141 | extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, |
142 | unsigned long val, void *v); |
143 | extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh, |
144 | unsigned long val, void *v, int nr_to_call, int *nr_calls); |
145 | extern int raw_notifier_call_chain(struct raw_notifier_head *nh, |
146 | unsigned long val, void *v); |
147 | extern int __raw_notifier_call_chain(struct raw_notifier_head *nh, |
148 | unsigned long val, void *v, int nr_to_call, int *nr_calls); |
149 | extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, |
150 | unsigned long val, void *v); |
151 | extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh, |
152 | unsigned long val, void *v, int nr_to_call, int *nr_calls); |
153 | |
154 | #define NOTIFY_DONE 0x0000 /* Don't care */ |
155 | #define NOTIFY_OK 0x0001 /* Suits me */ |
156 | #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ |
157 | #define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) |
158 | /* Bad/Veto action */ |
159 | /* |
160 | * Clean way to return from the notifier and stop further calls. |
161 | */ |
162 | #define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK) |
163 | |
164 | /* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */ |
165 | static inline int notifier_from_errno(int err) |
166 | { |
167 | if (err) |
168 | return NOTIFY_STOP_MASK | (NOTIFY_OK - err); |
169 | |
170 | return NOTIFY_OK; |
171 | } |
172 | |
173 | /* Restore (negative) errno value from notify return value. */ |
174 | static inline int notifier_to_errno(int ret) |
175 | { |
176 | ret &= ~NOTIFY_STOP_MASK; |
177 | return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0; |
178 | } |
179 | |
180 | /* |
181 | * Declared notifiers so far. I can imagine quite a few more chains |
182 | * over time (eg laptop power reset chains, reboot chain (to clean |
183 | * device units up), device [un]mount chain, module load/unload chain, |
184 | * low memory chain, screenblank chain (for plug in modular screenblankers) |
185 | * VC switch chains (for loadable kernel svgalib VC switch helpers) etc... |
186 | */ |
187 | |
188 | /* CPU notfiers are defined in include/linux/cpu.h. */ |
189 | |
190 | /* netdevice notifiers are defined in include/linux/netdevice.h */ |
191 | |
192 | /* reboot notifiers are defined in include/linux/reboot.h. */ |
193 | |
194 | /* Hibernation and suspend events are defined in include/linux/suspend.h. */ |
195 | |
196 | /* Virtual Terminal events are defined in include/linux/vt.h. */ |
197 | |
198 | #define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ |
199 | |
200 | /* Console keyboard events. |
201 | * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and |
202 | * KBD_KEYSYM. */ |
203 | #define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */ |
204 | #define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */ |
205 | #define KBD_UNICODE 0x0003 /* Keyboard unicode */ |
206 | #define KBD_KEYSYM 0x0004 /* Keyboard keysym */ |
207 | #define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */ |
208 | |
209 | extern struct blocking_notifier_head reboot_notifier_list; |
210 | |
211 | #endif /* __KERNEL__ */ |
212 | #endif /* _LINUX_NOTIFIER_H */ |
213 |
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