/* * Routines to manage notifier chains for passing status changes to any * interested routines. We need this instead of hard coded call lists so * that modules can poke their nose into the innards. The network devices * needed them so here they are for the rest of you. * * Alan Cox */ #ifndef _LINUX_NOTIFIER_H #define _LINUX_NOTIFIER_H #include #include #include #include /* * Notifier chains are of four types: * * Atomic notifier chains: Chain callbacks run in interrupt/atomic * context. Callouts are not allowed to block. * Blocking notifier chains: Chain callbacks run in process context. * Callouts are allowed to block. * Raw notifier chains: There are no restrictions on callbacks, * registration, or unregistration. All locking and protection * must be provided by the caller. * SRCU notifier chains: A variant of blocking notifier chains, with * the same restrictions. * * atomic_notifier_chain_register() may be called from an atomic context, * but blocking_notifier_chain_register() and srcu_notifier_chain_register() * must be called from a process context. Ditto for the corresponding * _unregister() routines. * * atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(), * and srcu_notifier_chain_unregister() _must not_ be called from within * the call chain. * * SRCU notifier chains are an alternative form of blocking notifier chains. * They use SRCU (Sleepable Read-Copy Update) instead of rw-semaphores for * protection of the chain links. This means there is _very_ low overhead * in srcu_notifier_call_chain(): no cache bounces and no memory barriers. * As compensation, srcu_notifier_chain_unregister() is rather expensive. * SRCU notifier chains should be used when the chain will be called very * often but notifier_blocks will seldom be removed. Also, SRCU notifier * chains are slightly more difficult to use because they require special * runtime initialization. */ struct notifier_block { int (*notifier_call)(struct notifier_block *, unsigned long, void *); struct notifier_block *next; int priority; }; struct atomic_notifier_head { spinlock_t lock; struct notifier_block *head; }; struct blocking_notifier_head { struct rw_semaphore rwsem; struct notifier_block *head; }; struct raw_notifier_head { struct notifier_block *head; }; struct srcu_notifier_head { struct mutex mutex; struct srcu_struct srcu; struct notifier_block *head; }; #define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \ spin_lock_init(&(name)->lock); \ (name)->head = NULL; \ } while (0) #define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \ init_rwsem(&(name)->rwsem); \ (name)->head = NULL; \ } while (0) #define RAW_INIT_NOTIFIER_HEAD(name) do { \ (name)->head = NULL; \ } while (0) /* srcu_notifier_heads must be initialized and cleaned up dynamically */ extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); #define srcu_cleanup_notifier_head(name) \ cleanup_srcu_struct(&(name)->srcu); #define ATOMIC_NOTIFIER_INIT(name) { \ .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ .head = NULL } #define BLOCKING_NOTIFIER_INIT(name) { \ .rwsem = __RWSEM_INITIALIZER((name).rwsem), \ .head = NULL } #define RAW_NOTIFIER_INIT(name) { \ .head = NULL } /* srcu_notifier_heads cannot be initialized statically */ #define ATOMIC_NOTIFIER_HEAD(name) \ struct atomic_notifier_head name = \ ATOMIC_NOTIFIER_INIT(name) #define BLOCKING_NOTIFIER_HEAD(name) \ struct blocking_notifier_head name = \ BLOCKING_NOTIFIER_INIT(name) #define RAW_NOTIFIER_HEAD(name) \ struct raw_notifier_head name = \ RAW_NOTIFIER_INIT(name) #ifdef __KERNEL__ extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh, struct notifier_block *nb); extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh, struct notifier_block *nb); extern int raw_notifier_chain_register(struct raw_notifier_head *nh, struct notifier_block *nb); extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, struct notifier_block *nb); extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, struct notifier_block *nb); extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, struct notifier_block *nb); extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, struct notifier_block *nb); extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, struct notifier_block *nb); extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, unsigned long val, void *v); extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh, unsigned long val, void *v, int nr_to_call, int *nr_calls); extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, unsigned long val, void *v); extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh, unsigned long val, void *v, int nr_to_call, int *nr_calls); extern int raw_notifier_call_chain(struct raw_notifier_head *nh, unsigned long val, void *v); extern int __raw_notifier_call_chain(struct raw_notifier_head *nh, unsigned long val, void *v, int nr_to_call, int *nr_calls); extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, unsigned long val, void *v); extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh, unsigned long val, void *v, int nr_to_call, int *nr_calls); #define NOTIFY_DONE 0x0000 /* Don't care */ #define NOTIFY_OK 0x0001 /* Suits me */ #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ #define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) /* Bad/Veto action */ /* * Clean way to return from the notifier and stop further calls. */ #define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK) /* * Declared notifiers so far. I can imagine quite a few more chains * over time (eg laptop power reset chains, reboot chain (to clean * device units up), device [un]mount chain, module load/unload chain, * low memory chain, screenblank chain (for plug in modular screenblankers) * VC switch chains (for loadable kernel svgalib VC switch helpers) etc... */ /* netdevice notifier chain */ #define NETDEV_UP 0x0001 /* For now you can't veto a device up/down */ #define NETDEV_DOWN 0x0002 #define NETDEV_REBOOT 0x0003 /* Tell a protocol stack a network interface detected a hardware crash and restarted - we can use this eg to kick tcp sessions once done */ #define NETDEV_CHANGE 0x0004 /* Notify device state change */ #define NETDEV_REGISTER 0x0005 #define NETDEV_UNREGISTER 0x0006 #define NETDEV_CHANGEMTU 0x0007 #define NETDEV_CHANGEADDR 0x0008 #define NETDEV_GOING_DOWN 0x0009 #define NETDEV_CHANGENAME 0x000A #define NETDEV_FEAT_CHANGE 0x000B #define SYS_DOWN 0x0001 /* Notify of system down */ #define SYS_RESTART SYS_DOWN #define SYS_HALT 0x0002 /* Notify of system halt */ #define SYS_POWER_OFF 0x0003 /* Notify of system power off */ #define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ #define CPU_ONLINE 0x0002 /* CPU (unsigned)v is up */ #define CPU_UP_PREPARE 0x0003 /* CPU (unsigned)v coming up */ #define CPU_UP_CANCELED 0x0004 /* CPU (unsigned)v NOT coming up */ #define CPU_DOWN_PREPARE 0x0005 /* CPU (unsigned)v going down */ #define CPU_DOWN_FAILED 0x0006 /* CPU (unsigned)v NOT going down */ #define CPU_DEAD 0x0007 /* CPU (unsigned)v dead */ #endif /* __KERNEL__ */ #endif /* _LINUX_NOTIFIER_H */