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include/linux/notifier.h
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/* SPDX-License-Identifier: GPL-2.0 */ |
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/* * 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> |
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#include <linux/mutex.h> #include <linux/rwsem.h> |
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#include <linux/srcu.h> |
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/* |
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* Notifier chains are of four types: |
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* * 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. |
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* SRCU notifier chains: A variant of blocking notifier chains, with * the same restrictions. |
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* * atomic_notifier_chain_register() may be called from an atomic context, |
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* but blocking_notifier_chain_register() and srcu_notifier_chain_register() * must be called from a process context. Ditto for the corresponding * _unregister() routines. |
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* |
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* 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. |
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*/ |
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struct notifier_block; |
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typedef int (*notifier_fn_t)(struct notifier_block *nb, unsigned long action, void *data); |
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struct notifier_block { |
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notifier_fn_t notifier_call; |
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struct notifier_block __rcu *next; |
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int priority; }; |
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struct atomic_notifier_head { spinlock_t lock; |
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struct notifier_block __rcu *head; |
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}; struct blocking_notifier_head { struct rw_semaphore rwsem; |
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struct notifier_block __rcu *head; |
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}; struct raw_notifier_head { |
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struct notifier_block __rcu *head; |
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}; |
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struct srcu_notifier_head { struct mutex mutex; struct srcu_struct srcu; |
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struct notifier_block __rcu *head; |
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}; |
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#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) |
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/* 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); |
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#define ATOMIC_NOTIFIER_INIT(name) { \ |
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.lock = __SPIN_LOCK_UNLOCKED(name.lock), \ |
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.head = NULL } #define BLOCKING_NOTIFIER_INIT(name) { \ .rwsem = __RWSEM_INITIALIZER((name).rwsem), \ .head = NULL } #define RAW_NOTIFIER_INIT(name) { \ .head = NULL } |
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/* srcu_notifier_heads cannot be initialized statically */ |
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#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) |
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#ifdef __KERNEL__ |
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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); |
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extern int blocking_notifier_chain_cond_register( struct blocking_notifier_head *nh, struct notifier_block *nb); |
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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, |
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unsigned long val, void *v); |
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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, |
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unsigned long val, void *v); |
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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, |
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unsigned long val, void *v); |
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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, |
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unsigned long val, void *v); |
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extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh, unsigned long val, void *v, int nr_to_call, int *nr_calls); |
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#define NOTIFY_DONE 0x0000 /* Don't care */ #define NOTIFY_OK 0x0001 /* Suits me */ #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ |
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#define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) /* Bad/Veto action */ |
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/* * Clean way to return from the notifier and stop further calls. */ #define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK) |
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/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */ static inline int notifier_from_errno(int err) { |
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if (err) return NOTIFY_STOP_MASK | (NOTIFY_OK - err); return NOTIFY_OK; |
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} /* 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; } |
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/* * 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... */ |
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/* CPU notfiers are defined in include/linux/cpu.h. */ |
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/* netdevice notifiers are defined in include/linux/netdevice.h */ |
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/* reboot notifiers are defined in include/linux/reboot.h. */ |
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/* Hibernation and suspend events are defined in include/linux/suspend.h. */ |
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/* Virtual Terminal events are defined in include/linux/vt.h. */ |
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#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ |
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/* 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 */ |
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extern struct blocking_notifier_head reboot_notifier_list; |
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#endif /* __KERNEL__ */ #endif /* _LINUX_NOTIFIER_H */ |