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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
49struct notifier_block;
50
51typedef int (*notifier_fn_t)(struct notifier_block *nb,
52 unsigned long action, void *data);
53
54struct notifier_block {
55 notifier_fn_t notifier_call;
56 struct notifier_block __rcu *next;
57 int priority;
58};
59
60struct atomic_notifier_head {
61 spinlock_t lock;
62 struct notifier_block __rcu *head;
63};
64
65struct blocking_notifier_head {
66 struct rw_semaphore rwsem;
67 struct notifier_block __rcu *head;
68};
69
70struct raw_notifier_head {
71 struct notifier_block __rcu *head;
72};
73
74struct srcu_notifier_head {
75 struct mutex mutex;
76#ifdef CONFIG_TREE_SRCU
77 struct srcu_usage srcuu;
78#endif
79 struct srcu_struct srcu;
80 struct notifier_block __rcu *head;
81};
82
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
95/* srcu_notifier_heads must be cleaned up dynamically */
96extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
97#define srcu_cleanup_notifier_head(name) \
98 cleanup_srcu_struct(&(name)->srcu);
99
100#define ATOMIC_NOTIFIER_INIT(name) { \
101 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \
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 }
108
109#define SRCU_NOTIFIER_INIT(name, pcpu) \
110 { \
111 .mutex = __MUTEX_INITIALIZER(name.mutex), \
112 .head = NULL, \
113 .srcu = __SRCU_STRUCT_INIT(name.srcu, name.srcuu, pcpu), \
114 }
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)
125
126#ifdef CONFIG_TREE_SRCU
127#define _SRCU_NOTIFIER_HEAD(name, mod) \
128 static DEFINE_PER_CPU(struct srcu_data, name##_head_srcu_data); \
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
145#ifdef __KERNEL__
146
147extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
148 struct notifier_block *nb);
149extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
150 struct notifier_block *nb);
151extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
152 struct notifier_block *nb);
153extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
154 struct notifier_block *nb);
155
156extern int atomic_notifier_chain_register_unique_prio(
157 struct atomic_notifier_head *nh, struct notifier_block *nb);
158extern int blocking_notifier_chain_register_unique_prio(
159 struct blocking_notifier_head *nh, struct notifier_block *nb);
160
161extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
162 struct notifier_block *nb);
163extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
164 struct notifier_block *nb);
165extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
166 struct notifier_block *nb);
167extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
168 struct notifier_block *nb);
169
170extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
171 unsigned long val, void *v);
172extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
173 unsigned long val, void *v);
174extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
175 unsigned long val, void *v);
176extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
177 unsigned long val, void *v);
178
179extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh,
180 unsigned long val_up, unsigned long val_down, void *v);
181extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh,
182 unsigned long val_up, unsigned long val_down, void *v);
183
184extern bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh);
185
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 */
189#define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002)
190 /* Bad/Veto action */
191/*
192 * Clean way to return from the notifier and stop further calls.
193 */
194#define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK)
195
196/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */
197static inline int notifier_from_errno(int err)
198{
199 if (err)
200 return NOTIFY_STOP_MASK | (NOTIFY_OK - err);
201
202 return NOTIFY_OK;
203}
204
205/* Restore (negative) errno value from notify return value. */
206static inline int notifier_to_errno(int ret)
207{
208 ret &= ~NOTIFY_STOP_MASK;
209 return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;
210}
211
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
220/* CPU notfiers are defined in include/linux/cpu.h. */
221
222/* netdevice notifiers are defined in include/linux/netdevice.h */
223
224/* reboot notifiers are defined in include/linux/reboot.h. */
225
226/* Hibernation and suspend events are defined in include/linux/suspend.h. */
227
228/* Virtual Terminal events are defined in include/linux/vt.h. */
229
230#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */
231
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
241extern struct blocking_notifier_head reboot_notifier_list;
242
243#endif /* __KERNEL__ */
244#endif /* _LINUX_NOTIFIER_H */