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