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 int (*notifier_call)(struct notifier_block *, unsigned long, void *); 52 struct notifier_block __rcu *next; 53 int priority; 54 }; 55 56 struct atomic_notifier_head { 57 spinlock_t lock; 58 struct notifier_block __rcu *head; 59 }; 60 61 struct blocking_notifier_head { 62 struct rw_semaphore rwsem; 63 struct notifier_block __rcu *head; 64 }; 65 66 struct raw_notifier_head { 67 struct notifier_block __rcu *head; 68 }; 69 70 struct srcu_notifier_head { 71 struct mutex mutex; 72 struct srcu_struct srcu; 73 struct notifier_block __rcu *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 */ 89 extern 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__ 114 115 extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh, 116 struct notifier_block *nb); 117 extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh, 118 struct notifier_block *nb); 119 extern int raw_notifier_chain_register(struct raw_notifier_head *nh, 120 struct notifier_block *nb); 121 extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, 122 struct notifier_block *nb); 123 124 extern int blocking_notifier_chain_cond_register( 125 struct blocking_notifier_head *nh, 126 struct notifier_block *nb); 127 128 extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, 129 struct notifier_block *nb); 130 extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, 131 struct notifier_block *nb); 132 extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, 133 struct notifier_block *nb); 134 extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, 135 struct notifier_block *nb); 136 137 extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, 138 unsigned long val, void *v); 139 extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh, 140 unsigned long val, void *v, int nr_to_call, int *nr_calls); 141 extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, 142 unsigned long val, void *v); 143 extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh, 144 unsigned long val, void *v, int nr_to_call, int *nr_calls); 145 extern int raw_notifier_call_chain(struct raw_notifier_head *nh, 146 unsigned long val, void *v); 147 extern int __raw_notifier_call_chain(struct raw_notifier_head *nh, 148 unsigned long val, void *v, int nr_to_call, int *nr_calls); 149 extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, 150 unsigned long val, void *v); 151 extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh, 152 unsigned long val, void *v, int nr_to_call, int *nr_calls); 153 154 #define NOTIFY_DONE 0x0000 /* Don't care */ 155 #define NOTIFY_OK 0x0001 /* Suits me */ 156 #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ 157 #define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) 158 /* Bad/Veto action */ 159 /* 160 * Clean way to return from the notifier and stop further calls. 161 */ 162 #define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK) 163 164 /* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */ 165 static inline int notifier_from_errno(int err) 166 { 167 if (err) 168 return NOTIFY_STOP_MASK | (NOTIFY_OK - err); 169 170 return NOTIFY_OK; 171 } 172 173 /* Restore (negative) errno value from notify return value. */ 174 static inline int notifier_to_errno(int ret) 175 { 176 ret &= ~NOTIFY_STOP_MASK; 177 return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0; 178 } 179 180 /* 181 * Declared notifiers so far. I can imagine quite a few more chains 182 * over time (eg laptop power reset chains, reboot chain (to clean 183 * device units up), device [un]mount chain, module load/unload chain, 184 * low memory chain, screenblank chain (for plug in modular screenblankers) 185 * VC switch chains (for loadable kernel svgalib VC switch helpers) etc... 186 */ 187 188 /* CPU notfiers are defined in include/linux/cpu.h. */ 189 190 /* netdevice notifier chain. Please remember to update the rtnetlink 191 * notification exclusion list in rtnetlink_event() when adding new 192 * types. 193 */ 194 #define NETDEV_UP 0x0001 /* For now you can't veto a device up/down */ 195 #define NETDEV_DOWN 0x0002 196 #define NETDEV_REBOOT 0x0003 /* Tell a protocol stack a network interface 197 detected a hardware crash and restarted 198 - we can use this eg to kick tcp sessions 199 once done */ 200 #define NETDEV_CHANGE 0x0004 /* Notify device state change */ 201 #define NETDEV_REGISTER 0x0005 202 #define NETDEV_UNREGISTER 0x0006 203 #define NETDEV_CHANGEMTU 0x0007 204 #define NETDEV_CHANGEADDR 0x0008 205 #define NETDEV_GOING_DOWN 0x0009 206 #define NETDEV_CHANGENAME 0x000A 207 #define NETDEV_FEAT_CHANGE 0x000B 208 #define NETDEV_BONDING_FAILOVER 0x000C 209 #define NETDEV_PRE_UP 0x000D 210 #define NETDEV_PRE_TYPE_CHANGE 0x000E 211 #define NETDEV_POST_TYPE_CHANGE 0x000F 212 #define NETDEV_POST_INIT 0x0010 213 #define NETDEV_UNREGISTER_BATCH 0x0011 214 #define NETDEV_RELEASE 0x0012 215 #define NETDEV_NOTIFY_PEERS 0x0013 216 #define NETDEV_JOIN 0x0014 217 218 #define SYS_DOWN 0x0001 /* Notify of system down */ 219 #define SYS_RESTART SYS_DOWN 220 #define SYS_HALT 0x0002 /* Notify of system halt */ 221 #define SYS_POWER_OFF 0x0003 /* Notify of system power off */ 222 223 #define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ 224 225 /* Hibernation and suspend events */ 226 #define PM_HIBERNATION_PREPARE 0x0001 /* Going to hibernate */ 227 #define PM_POST_HIBERNATION 0x0002 /* Hibernation finished */ 228 #define PM_SUSPEND_PREPARE 0x0003 /* Going to suspend the system */ 229 #define PM_POST_SUSPEND 0x0004 /* Suspend finished */ 230 #define PM_RESTORE_PREPARE 0x0005 /* Going to restore a saved image */ 231 #define PM_POST_RESTORE 0x0006 /* Restore failed */ 232 233 /* Console keyboard events. 234 * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and 235 * KBD_KEYSYM. */ 236 #define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */ 237 #define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */ 238 #define KBD_UNICODE 0x0003 /* Keyboard unicode */ 239 #define KBD_KEYSYM 0x0004 /* Keyboard keysym */ 240 #define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */ 241 242 extern struct blocking_notifier_head reboot_notifier_list; 243 244 /* Virtual Terminal events. */ 245 #define VT_ALLOCATE 0x0001 /* Console got allocated */ 246 #define VT_DEALLOCATE 0x0002 /* Console will be deallocated */ 247 #define VT_WRITE 0x0003 /* A char got output */ 248 #define VT_UPDATE 0x0004 /* A bigger update occurred */ 249 #define VT_PREWRITE 0x0005 /* A char is about to be written to the console */ 250 251 #endif /* __KERNEL__ */ 252 #endif /* _LINUX_NOTIFIER_H */ 253