notifier.h (8356B)
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 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 */ 93extern 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 144extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh, 145 struct notifier_block *nb); 146extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh, 147 struct notifier_block *nb); 148extern int raw_notifier_chain_register(struct raw_notifier_head *nh, 149 struct notifier_block *nb); 150extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, 151 struct notifier_block *nb); 152 153extern int atomic_notifier_chain_register_unique_prio( 154 struct atomic_notifier_head *nh, struct notifier_block *nb); 155extern int blocking_notifier_chain_register_unique_prio( 156 struct blocking_notifier_head *nh, struct notifier_block *nb); 157 158extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, 159 struct notifier_block *nb); 160extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, 161 struct notifier_block *nb); 162extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, 163 struct notifier_block *nb); 164extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, 165 struct notifier_block *nb); 166 167extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, 168 unsigned long val, void *v); 169extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, 170 unsigned long val, void *v); 171extern int raw_notifier_call_chain(struct raw_notifier_head *nh, 172 unsigned long val, void *v); 173extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, 174 unsigned long val, void *v); 175 176extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh, 177 unsigned long val_up, unsigned long val_down, void *v); 178extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, 179 unsigned long val_up, unsigned long val_down, void *v); 180 181extern 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). */ 194static 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. */ 203static 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 238extern struct blocking_notifier_head reboot_notifier_list; 239 240#endif /* __KERNEL__ */ 241#endif /* _LINUX_NOTIFIER_H */