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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
50struct notifier_block {
51 int (*notifier_call)(struct notifier_block *, unsigned long, void *);
52 struct notifier_block *next;
53 int priority;
54};
55
56struct atomic_notifier_head {
57 spinlock_t lock;
58 struct notifier_block *head;
59};
60
61struct blocking_notifier_head {
62 struct rw_semaphore rwsem;
63 struct notifier_block *head;
64};
65
66struct raw_notifier_head {
67 struct notifier_block *head;
68};
69
70struct srcu_notifier_head {
71 struct mutex mutex;
72 struct srcu_struct srcu;
73 struct notifier_block *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 */
89extern 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
115extern int atomic_notifier_chain_register(struct atomic_notifier_head *,
116 struct notifier_block *);
117extern int blocking_notifier_chain_register(struct blocking_notifier_head *,
118 struct notifier_block *);
119extern int raw_notifier_chain_register(struct raw_notifier_head *,
120 struct notifier_block *);
121extern int srcu_notifier_chain_register(struct srcu_notifier_head *,
122 struct notifier_block *);
123
124extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *,
125 struct notifier_block *);
126extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *,
127 struct notifier_block *);
128extern int raw_notifier_chain_unregister(struct raw_notifier_head *,
129 struct notifier_block *);
130extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *,
131 struct notifier_block *);
132
133extern int atomic_notifier_call_chain(struct atomic_notifier_head *,
134 unsigned long val, void *v);
135extern int blocking_notifier_call_chain(struct blocking_notifier_head *,
136 unsigned long val, void *v);
137extern int raw_notifier_call_chain(struct raw_notifier_head *,
138 unsigned long val, void *v);
139extern int srcu_notifier_call_chain(struct srcu_notifier_head *,
140 unsigned long val, void *v);
141
142#define NOTIFY_DONE 0x0000 /* Don't care */
143#define NOTIFY_OK 0x0001 /* Suits me */
144#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
145#define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002)
146 /* Bad/Veto action */
147/*
148 * Clean way to return from the notifier and stop further calls.
149 */
150#define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK)
151
152/*
153 * Declared notifiers so far. I can imagine quite a few more chains
154 * over time (eg laptop power reset chains, reboot chain (to clean
155 * device units up), device [un]mount chain, module load/unload chain,
156 * low memory chain, screenblank chain (for plug in modular screenblankers)
157 * VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
158 */
159
160/* netdevice notifier chain */
161#define NETDEV_UP 0x0001 /* For now you can't veto a device up/down */
162#define NETDEV_DOWN 0x0002
163#define NETDEV_REBOOT 0x0003 /* Tell a protocol stack a network interface
164 detected a hardware crash and restarted
165 - we can use this eg to kick tcp sessions
166 once done */
167#define NETDEV_CHANGE 0x0004 /* Notify device state change */
168#define NETDEV_REGISTER 0x0005
169#define NETDEV_UNREGISTER 0x0006
170#define NETDEV_CHANGEMTU 0x0007
171#define NETDEV_CHANGEADDR 0x0008
172#define NETDEV_GOING_DOWN 0x0009
173#define NETDEV_CHANGENAME 0x000A
174#define NETDEV_FEAT_CHANGE 0x000B
175
176#define SYS_DOWN 0x0001 /* Notify of system down */
177#define SYS_RESTART SYS_DOWN
178#define SYS_HALT 0x0002 /* Notify of system halt */
179#define SYS_POWER_OFF 0x0003 /* Notify of system power off */
180
181#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */
182
183#define CPU_ONLINE 0x0002 /* CPU (unsigned)v is up */
184#define CPU_UP_PREPARE 0x0003 /* CPU (unsigned)v coming up */
185#define CPU_UP_CANCELED 0x0004 /* CPU (unsigned)v NOT coming up */
186#define CPU_DOWN_PREPARE 0x0005 /* CPU (unsigned)v going down */
187#define CPU_DOWN_FAILED 0x0006 /* CPU (unsigned)v NOT going down */
188#define CPU_DEAD 0x0007 /* CPU (unsigned)v dead */
189
190#endif /* __KERNEL__ */
191#endif /* _LINUX_NOTIFIER_H */