| /* SPDX-License-Identifier: GPL-2.0 */ |
| /* |
| * 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. |
| */ |
| |
| struct notifier_block; |
| |
| 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 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 } |
| |
| #define SRCU_NOTIFIER_INIT(name, pcpu) \ |
| { \ |
| .mutex = __MUTEX_INITIALIZER(name.mutex), \ |
| .head = NULL, \ |
| .srcu = __SRCU_STRUCT_INIT(name.srcu, pcpu), \ |
| } |
| |
| #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 CONFIG_TREE_SRCU |
| #define _SRCU_NOTIFIER_HEAD(name, mod) \ |
| static DEFINE_PER_CPU(struct srcu_data, name##_head_srcu_data); \ |
| mod struct srcu_notifier_head name = \ |
| SRCU_NOTIFIER_INIT(name, name##_head_srcu_data) |
| |
| #else |
| #define _SRCU_NOTIFIER_HEAD(name, mod) \ |
| mod struct srcu_notifier_head name = \ |
| SRCU_NOTIFIER_INIT(name, name) |
| |
| #endif |
| |
| #define SRCU_NOTIFIER_HEAD(name) \ |
| _SRCU_NOTIFIER_HEAD(name, /* not static */) |
| |
| #define SRCU_NOTIFIER_HEAD_STATIC(name) \ |
| _SRCU_NOTIFIER_HEAD(name, static) |
| |
| #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 blocking_notifier_call_chain(struct blocking_notifier_head *nh, |
| unsigned long val, void *v); |
| extern int raw_notifier_call_chain(struct raw_notifier_head *nh, |
| unsigned long val, void *v); |
| extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, |
| unsigned long val, void *v); |
| |
| extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh, |
| unsigned long val_up, unsigned long val_down, void *v); |
| extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, |
| unsigned long val_up, unsigned long val_down, void *v); |
| |
| #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 */ |