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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 *nh,
116 struct notifier_block *nb);
117extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
118 struct notifier_block *nb);
119extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
120 struct notifier_block *nb);
121extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
122 struct notifier_block *nb);
123
124extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
125 struct notifier_block *nb);
126extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
127 struct notifier_block *nb);
128extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
129 struct notifier_block *nb);
130extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
131 struct notifier_block *nb);
132
133extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
134 unsigned long val, void *v);
135extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
136 unsigned long val, void *v, int nr_to_call, int *nr_calls);
137extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
138 unsigned long val, void *v);
139extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
140 unsigned long val, void *v, int nr_to_call, int *nr_calls);
141extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
142 unsigned long val, void *v);
143extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
144 unsigned long val, void *v, int nr_to_call, int *nr_calls);
145extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
146 unsigned long val, void *v);
147extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
148 unsigned long val, void *v, int nr_to_call, int *nr_calls);
149
150#define NOTIFY_DONE 0x0000 /* Don't care */
151#define NOTIFY_OK 0x0001 /* Suits me */
152#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */
153#define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002)
154 /* Bad/Veto action */
155/*
156 * Clean way to return from the notifier and stop further calls.
157 */
158#define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK)
159
160/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */
161static inline int notifier_from_errno(int err)
162{
163 return NOTIFY_STOP_MASK | (NOTIFY_OK - err);
164}
165
166/* Restore (negative) errno value from notify return value. */
167static inline int notifier_to_errno(int ret)
168{
169 ret &= ~NOTIFY_STOP_MASK;
170 return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;
171}
172
173/*
174 * Declared notifiers so far. I can imagine quite a few more chains
175 * over time (eg laptop power reset chains, reboot chain (to clean
176 * device units up), device [un]mount chain, module load/unload chain,
177 * low memory chain, screenblank chain (for plug in modular screenblankers)
178 * VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
179 */
180
181/* netdevice notifier chain */
182#define NETDEV_UP 0x0001 /* For now you can't veto a device up/down */
183#define NETDEV_DOWN 0x0002
184#define NETDEV_REBOOT 0x0003 /* Tell a protocol stack a network interface
185 detected a hardware crash and restarted
186 - we can use this eg to kick tcp sessions
187 once done */
188#define NETDEV_CHANGE 0x0004 /* Notify device state change */
189#define NETDEV_REGISTER 0x0005
190#define NETDEV_UNREGISTER 0x0006
191#define NETDEV_CHANGEMTU 0x0007
192#define NETDEV_CHANGEADDR 0x0008
193#define NETDEV_GOING_DOWN 0x0009
194#define NETDEV_CHANGENAME 0x000A
195#define NETDEV_FEAT_CHANGE 0x000B
196
197#define SYS_DOWN 0x0001 /* Notify of system down */
198#define SYS_RESTART SYS_DOWN
199#define SYS_HALT 0x0002 /* Notify of system halt */
200#define SYS_POWER_OFF 0x0003 /* Notify of system power off */
201
202#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */
203
204#define CPU_ONLINE 0x0002 /* CPU (unsigned)v is up */
205#define CPU_UP_PREPARE 0x0003 /* CPU (unsigned)v coming up */
206#define CPU_UP_CANCELED 0x0004 /* CPU (unsigned)v NOT coming up */
207#define CPU_DOWN_PREPARE 0x0005 /* CPU (unsigned)v going down */
208#define CPU_DOWN_FAILED 0x0006 /* CPU (unsigned)v NOT going down */
209#define CPU_DEAD 0x0007 /* CPU (unsigned)v dead */
210#define CPU_LOCK_ACQUIRE 0x0008 /* Acquire all hotcpu locks */
211#define CPU_LOCK_RELEASE 0x0009 /* Release all hotcpu locks */
212#define CPU_DYING 0x000A /* CPU (unsigned)v not running any task,
213 * not handling interrupts, soon dead */
214
215/* Used for CPU hotplug events occuring while tasks are frozen due to a suspend
216 * operation in progress
217 */
218#define CPU_TASKS_FROZEN 0x0010
219
220#define CPU_ONLINE_FROZEN (CPU_ONLINE | CPU_TASKS_FROZEN)
221#define CPU_UP_PREPARE_FROZEN (CPU_UP_PREPARE | CPU_TASKS_FROZEN)
222#define CPU_UP_CANCELED_FROZEN (CPU_UP_CANCELED | CPU_TASKS_FROZEN)
223#define CPU_DOWN_PREPARE_FROZEN (CPU_DOWN_PREPARE | CPU_TASKS_FROZEN)
224#define CPU_DOWN_FAILED_FROZEN (CPU_DOWN_FAILED | CPU_TASKS_FROZEN)
225#define CPU_DEAD_FROZEN (CPU_DEAD | CPU_TASKS_FROZEN)
226#define CPU_DYING_FROZEN (CPU_DYING | CPU_TASKS_FROZEN)
227
228/* Hibernation and suspend events */
229#define PM_HIBERNATION_PREPARE 0x0001 /* Going to hibernate */
230#define PM_POST_HIBERNATION 0x0002 /* Hibernation finished */
231#define PM_SUSPEND_PREPARE 0x0003 /* Going to suspend the system */
232#define PM_POST_SUSPEND 0x0004 /* Suspend finished */
233
234#endif /* __KERNEL__ */
235#endif /* _LINUX_NOTIFIER_H */