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1/* SPDX-License-Identifier: GPL-2.0 */2/*3 * Routines to manage notifier chains for passing status changes to any4 * interested routines. We need this instead of hard coded call lists so5 * that modules can poke their nose into the innards. The network devices6 * needed them so here they are for the rest of you.7 *8 * Alan Cox <Alan.Cox@linux.org>9 */10 11#ifndef _LINUX_NOTIFIER_H12#define _LINUX_NOTIFIER_H13#include <linux/errno.h>14#include <linux/mutex.h>15#include <linux/rwsem.h>16#include <linux/srcu.h>17 18/*19 * Notifier chains are of four types:20 *21 * Atomic notifier chains: Chain callbacks run in interrupt/atomic22 * context. Callouts are not allowed to block.23 * Blocking notifier chains: Chain callbacks run in process context.24 * Callouts are allowed to block.25 * Raw notifier chains: There are no restrictions on callbacks,26 * registration, or unregistration. All locking and protection27 * must be provided by the caller.28 * SRCU notifier chains: A variant of blocking notifier chains, with29 * the same restrictions.30 *31 * atomic_notifier_chain_register() may be called from an atomic context,32 * but blocking_notifier_chain_register() and srcu_notifier_chain_register()33 * must be called from a process context. Ditto for the corresponding34 * _unregister() routines.35 *36 * atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(),37 * and srcu_notifier_chain_unregister() _must not_ be called from within38 * the call chain.39 *40 * SRCU notifier chains are an alternative form of blocking notifier chains.41 * They use SRCU (Sleepable Read-Copy Update) instead of rw-semaphores for42 * protection of the chain links. This means there is _very_ low overhead43 * in srcu_notifier_call_chain(): no cache bounces and no memory barriers.44 * As compensation, srcu_notifier_chain_unregister() is rather expensive.45 * SRCU notifier chains should be used when the chain will be called very46 * often but notifier_blocks will seldom be removed.47 */48 49struct notifier_block;50 51typedef int (*notifier_fn_t)(struct notifier_block *nb,52 unsigned long action, void *data);53 54struct notifier_block {55 notifier_fn_t notifier_call;56 struct notifier_block __rcu *next;57 int priority;58};59 60struct atomic_notifier_head {61 spinlock_t lock;62 struct notifier_block __rcu *head;63};64 65struct blocking_notifier_head {66 struct rw_semaphore rwsem;67 struct notifier_block __rcu *head;68};69 70struct raw_notifier_head {71 struct notifier_block __rcu *head;72};73 74struct srcu_notifier_head {75 struct mutex mutex;76 struct srcu_usage srcuu;77 struct srcu_struct srcu;78 struct notifier_block __rcu *head;79};80 81#define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \82 spin_lock_init(&(name)->lock); \83 (name)->head = NULL; \84 } while (0)85#define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \86 init_rwsem(&(name)->rwsem); \87 (name)->head = NULL; \88 } while (0)89#define RAW_INIT_NOTIFIER_HEAD(name) do { \90 (name)->head = NULL; \91 } while (0)92 93/* srcu_notifier_heads must be cleaned up dynamically */94extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);95#define srcu_cleanup_notifier_head(name) \96 cleanup_srcu_struct(&(name)->srcu);97 98#define ATOMIC_NOTIFIER_INIT(name) { \99 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \100 .head = NULL }101#define BLOCKING_NOTIFIER_INIT(name) { \102 .rwsem = __RWSEM_INITIALIZER((name).rwsem), \103 .head = NULL }104#define RAW_NOTIFIER_INIT(name) { \105 .head = NULL }106 107#define SRCU_NOTIFIER_INIT(name, pcpu) \108 { \109 .mutex = __MUTEX_INITIALIZER(name.mutex), \110 .head = NULL, \111 .srcuu = __SRCU_USAGE_INIT(name.srcuu), \112 .srcu = __SRCU_STRUCT_INIT(name.srcu, name.srcuu, pcpu), \113 }114 115#define ATOMIC_NOTIFIER_HEAD(name) \116 struct atomic_notifier_head name = \117 ATOMIC_NOTIFIER_INIT(name)118#define BLOCKING_NOTIFIER_HEAD(name) \119 struct blocking_notifier_head name = \120 BLOCKING_NOTIFIER_INIT(name)121#define RAW_NOTIFIER_HEAD(name) \122 struct raw_notifier_head name = \123 RAW_NOTIFIER_INIT(name)124 125#ifdef CONFIG_TREE_SRCU126#define _SRCU_NOTIFIER_HEAD(name, mod) \127 static DEFINE_PER_CPU(struct srcu_data, name##_head_srcu_data); \128 mod struct srcu_notifier_head name = \129 SRCU_NOTIFIER_INIT(name, name##_head_srcu_data)130 131#else132#define _SRCU_NOTIFIER_HEAD(name, mod) \133 mod struct srcu_notifier_head name = \134 SRCU_NOTIFIER_INIT(name, name)135 136#endif137 138#define SRCU_NOTIFIER_HEAD(name) \139 _SRCU_NOTIFIER_HEAD(name, /* not static */)140 141#define SRCU_NOTIFIER_HEAD_STATIC(name) \142 _SRCU_NOTIFIER_HEAD(name, static)143 144#ifdef __KERNEL__145 146extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,147 struct notifier_block *nb);148extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,149 struct notifier_block *nb) HWJS_SUSPENDS;150extern int raw_notifier_chain_register(struct raw_notifier_head *nh,151 struct notifier_block *nb);152extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,153 struct notifier_block *nb) HWJS_SUSPENDS;154 155extern int atomic_notifier_chain_register_unique_prio(156 struct atomic_notifier_head *nh, struct notifier_block *nb);157extern int blocking_notifier_chain_register_unique_prio(158 struct blocking_notifier_head *nh, struct notifier_block *nb) HWJS_SUSPENDS;159 160extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,161 struct notifier_block *nb) HWJS_SUSPENDS;162extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,163 struct notifier_block *nb) HWJS_SUSPENDS;164extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,165 struct notifier_block *nb);166extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,167 struct notifier_block *nb) HWJS_SUSPENDS;168 169extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,170 unsigned long val, void *v);171extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,172 unsigned long val, void *v) HWJS_SUSPENDS;173extern int raw_notifier_call_chain(struct raw_notifier_head *nh,174 unsigned long val, void *v);175extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,176 unsigned long val, void *v);177 178extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh,179 unsigned long val_up, unsigned long val_down, void *v) HWJS_SUSPENDS;180extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh,181 unsigned long val_up, unsigned long val_down, void *v);182 183extern bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh);184 185#define NOTIFY_DONE 0x0000 /* Don't care */186#define NOTIFY_OK 0x0001 /* Suits me */187#define NOTIFY_STOP_MASK 0x8000 /* Don't call further */188#define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002)189 /* Bad/Veto action */190/*191 * Clean way to return from the notifier and stop further calls.192 */193#define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK)194 195/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */196static inline int notifier_from_errno(int err)197{198 if (err)199 return NOTIFY_STOP_MASK | (NOTIFY_OK - err);200 201 return NOTIFY_OK;202}203 204/* Restore (negative) errno value from notify return value. */205static inline int notifier_to_errno(int ret)206{207 ret &= ~NOTIFY_STOP_MASK;208 return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;209}210 211/*212 * Declared notifiers so far. I can imagine quite a few more chains213 * over time (eg laptop power reset chains, reboot chain (to clean 214 * device units up), device [un]mount chain, module load/unload chain,215 * low memory chain, screenblank chain (for plug in modular screenblankers) 216 * VC switch chains (for loadable kernel svgalib VC switch helpers) etc...217 */218 219/* CPU notfiers are defined in include/linux/cpu.h. */220 221/* netdevice notifiers are defined in include/linux/netdevice.h */222 223/* reboot notifiers are defined in include/linux/reboot.h. */224 225/* Hibernation and suspend events are defined in include/linux/suspend.h. */226 227/* Virtual Terminal events are defined in include/linux/vt.h. */228 229#define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */230 231/* Console keyboard events.232 * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and233 * KBD_KEYSYM. */234#define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */235#define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */236#define KBD_UNICODE 0x0003 /* Keyboard unicode */237#define KBD_KEYSYM 0x0004 /* Keyboard keysym */238#define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */239 240extern struct blocking_notifier_head reboot_notifier_list;241 242#endif /* __KERNEL__ */243#endif /* _LINUX_NOTIFIER_H */244