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