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 <[email protected]> 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. Also, SRCU notifier 47 * chains are slightly more difficult to use because they require special 48 * runtime initialization. 49 */ 50 51 struct notifier_block; 52 53 typedef int (*notifier_fn_t)(struct notifier_block *nb, 54 unsigned long action, void *data); 55 56 struct notifier_block { 57 notifier_fn_t notifier_call; 58 struct notifier_block __rcu *next; 59 int priority; 60 }; 61 62 struct atomic_notifier_head { 63 spinlock_t lock; 64 struct notifier_block __rcu *head; 65 }; 66 67 struct blocking_notifier_head { 68 struct rw_semaphore rwsem; 69 struct notifier_block __rcu *head; 70 }; 71 72 struct raw_notifier_head { 73 struct notifier_block __rcu *head; 74 }; 75 76 struct srcu_notifier_head { 77 struct mutex mutex; 78 struct srcu_struct srcu; 79 struct notifier_block __rcu *head; 80 }; 81 82 #define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \ 83 spin_lock_init(&(name)->lock); \ 84 (name)->head = NULL; \ 85 } while (0) 86 #define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \ 87 init_rwsem(&(name)->rwsem); \ 88 (name)->head = NULL; \ 89 } while (0) 90 #define RAW_INIT_NOTIFIER_HEAD(name) do { \ 91 (name)->head = NULL; \ 92 } while (0) 93 94 /* srcu_notifier_heads must be initialized and cleaned up dynamically */ 95 extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); 96 #define srcu_cleanup_notifier_head(name) \ 97 cleanup_srcu_struct(&(name)->srcu); 98 99 #define ATOMIC_NOTIFIER_INIT(name) { \ 100 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ 101 .head = NULL } 102 #define BLOCKING_NOTIFIER_INIT(name) { \ 103 .rwsem = __RWSEM_INITIALIZER((name).rwsem), \ 104 .head = NULL } 105 #define RAW_NOTIFIER_INIT(name) { \ 106 .head = NULL } 107 /* srcu_notifier_heads cannot be initialized statically */ 108 109 #define ATOMIC_NOTIFIER_HEAD(name) \ 110 struct atomic_notifier_head name = \ 111 ATOMIC_NOTIFIER_INIT(name) 112 #define BLOCKING_NOTIFIER_HEAD(name) \ 113 struct blocking_notifier_head name = \ 114 BLOCKING_NOTIFIER_INIT(name) 115 #define RAW_NOTIFIER_HEAD(name) \ 116 struct raw_notifier_head name = \ 117 RAW_NOTIFIER_INIT(name) 118 119 #ifdef __KERNEL__ 120 121 extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh, 122 struct notifier_block *nb); 123 extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh, 124 struct notifier_block *nb); 125 extern int raw_notifier_chain_register(struct raw_notifier_head *nh, 126 struct notifier_block *nb); 127 extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, 128 struct notifier_block *nb); 129 130 extern int blocking_notifier_chain_cond_register( 131 struct blocking_notifier_head *nh, 132 struct notifier_block *nb); 133 134 extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, 135 struct notifier_block *nb); 136 extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, 137 struct notifier_block *nb); 138 extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, 139 struct notifier_block *nb); 140 extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, 141 struct notifier_block *nb); 142 143 extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, 144 unsigned long val, void *v); 145 extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh, 146 unsigned long val, void *v, int nr_to_call, int *nr_calls); 147 extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, 148 unsigned long val, void *v); 149 extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh, 150 unsigned long val, void *v, int nr_to_call, int *nr_calls); 151 extern int raw_notifier_call_chain(struct raw_notifier_head *nh, 152 unsigned long val, void *v); 153 extern int __raw_notifier_call_chain(struct raw_notifier_head *nh, 154 unsigned long val, void *v, int nr_to_call, int *nr_calls); 155 extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, 156 unsigned long val, void *v); 157 extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh, 158 unsigned long val, void *v, int nr_to_call, int *nr_calls); 159 160 #define NOTIFY_DONE 0x0000 /* Don't care */ 161 #define NOTIFY_OK 0x0001 /* Suits me */ 162 #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ 163 #define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) 164 /* Bad/Veto action */ 165 /* 166 * Clean way to return from the notifier and stop further calls. 167 */ 168 #define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK) 169 170 /* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */ 171 static inline int notifier_from_errno(int err) 172 { 173 if (err) 174 return NOTIFY_STOP_MASK | (NOTIFY_OK - err); 175 176 return NOTIFY_OK; 177 } 178 179 /* Restore (negative) errno value from notify return value. */ 180 static inline int notifier_to_errno(int ret) 181 { 182 ret &= ~NOTIFY_STOP_MASK; 183 return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0; 184 } 185 186 /* 187 * Declared notifiers so far. I can imagine quite a few more chains 188 * over time (eg laptop power reset chains, reboot chain (to clean 189 * device units up), device [un]mount chain, module load/unload chain, 190 * low memory chain, screenblank chain (for plug in modular screenblankers) 191 * VC switch chains (for loadable kernel svgalib VC switch helpers) etc... 192 */ 193 194 /* CPU notfiers are defined in include/linux/cpu.h. */ 195 196 /* netdevice notifiers are defined in include/linux/netdevice.h */ 197 198 /* reboot notifiers are defined in include/linux/reboot.h. */ 199 200 /* Hibernation and suspend events are defined in include/linux/suspend.h. */ 201 202 /* Virtual Terminal events are defined in include/linux/vt.h. */ 203 204 #define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ 205 206 /* Console keyboard events. 207 * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and 208 * KBD_KEYSYM. */ 209 #define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */ 210 #define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */ 211 #define KBD_UNICODE 0x0003 /* Keyboard unicode */ 212 #define KBD_KEYSYM 0x0004 /* Keyboard keysym */ 213 #define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */ 214 215 extern struct blocking_notifier_head reboot_notifier_list; 216 217 #endif /* __KERNEL__ */ 218 #endif /* _LINUX_NOTIFIER_H */ 219