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Diffstat (limited to 'include/linux/notifier.h')
| -rw-r--r-- | include/linux/notifier.h | 215 |
1 files changed, 215 insertions, 0 deletions
diff --git a/include/linux/notifier.h b/include/linux/notifier.h new file mode 100644 index 000000000..d14a4c362 --- /dev/null +++ b/include/linux/notifier.h @@ -0,0 +1,215 @@ +/* + * 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 <Alan.Cox@linux.org> + */ + +#ifndef _LINUX_NOTIFIER_H +#define _LINUX_NOTIFIER_H +#include <linux/errno.h> +#include <linux/mutex.h> +#include <linux/rwsem.h> +#include <linux/srcu.h> + +/* + * 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. + */ + +typedef int (*notifier_fn_t)(struct notifier_block *nb, + unsigned long action, void *data); + +struct notifier_block { + notifier_fn_t notifier_call; + struct notifier_block __rcu *next; + int priority; +}; + +struct atomic_notifier_head { + spinlock_t lock; + struct notifier_block __rcu *head; +}; + +struct blocking_notifier_head { + struct rw_semaphore rwsem; + struct notifier_block __rcu *head; +}; + +struct raw_notifier_head { + struct notifier_block __rcu *head; +}; + +struct srcu_notifier_head { + struct mutex mutex; + struct srcu_struct srcu; + struct notifier_block __rcu *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 blocking_notifier_chain_cond_register( + struct blocking_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) + +/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */ +static inline int notifier_from_errno(int err) +{ + if (err) + return NOTIFY_STOP_MASK | (NOTIFY_OK - err); + + return NOTIFY_OK; +} + +/* Restore (negative) errno value from notify return value. */ +static inline int notifier_to_errno(int ret) +{ + ret &= ~NOTIFY_STOP_MASK; + return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0; +} + +/* + * 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... + */ + +/* CPU notfiers are defined in include/linux/cpu.h. */ + +/* netdevice notifiers are defined in include/linux/netdevice.h */ + +/* reboot notifiers are defined in include/linux/reboot.h. */ + +/* Hibernation and suspend events are defined in include/linux/suspend.h. */ + +/* Virtual Terminal events are defined in include/linux/vt.h. */ + +#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ + +/* Console keyboard events. + * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and + * KBD_KEYSYM. */ +#define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */ +#define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */ +#define KBD_UNICODE 0x0003 /* Keyboard unicode */ +#define KBD_KEYSYM 0x0004 /* Keyboard keysym */ +#define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */ + +extern struct blocking_notifier_head reboot_notifier_list; + +#endif /* __KERNEL__ */ +#endif /* _LINUX_NOTIFIER_H */ |