1 /* SPDX-License-Identifier: GPL-2.0 */ 2 /* 3 * Routines to manage notifier chains for passing status changes to any 4 * interested routines. We need this instead of hard coded call lists so 5 * that modules can poke their nose into the innards. The network devices 6 * 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_H 12 #define _LINUX_NOTIFIER_H 13 #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/atomic 22 * 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 protection 27 * must be provided by the caller. 28 * SRCU notifier chains: A variant of blocking notifier chains, with 29 * 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 corresponding 34 * _unregister() routines. 35 * 36 * atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(), 37 * and srcu_notifier_chain_unregister() _must not_ be called from within 38 * 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 for 42 * protection of the chain links. This means there is _very_ low overhead 43 * 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 very 46 * often but notifier_blocks will seldom be removed. 47 */ 48 49 struct notifier_block; 50 51 typedef int (*notifier_fn_t)(struct notifier_block *nb, 52 unsigned long action, void *data); 53 54 struct notifier_block { 55 notifier_fn_t notifier_call; 56 struct notifier_block __rcu *next; 57 int priority; 58 }; 59 60 struct atomic_notifier_head { 61 spinlock_t lock; 62 struct notifier_block __rcu *head; 63 }; 64 65 struct blocking_notifier_head { 66 struct rw_semaphore rwsem; 67 struct notifier_block __rcu *head; 68 }; 69 70 struct raw_notifier_head { 71 struct notifier_block __rcu *head; 72 }; 73 74 struct 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 */ 94 extern 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_SRCU 126 #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 #else 132 #define _SRCU_NOTIFIER_HEAD(name, mod) \ 133 mod struct srcu_notifier_head name = \ 134 SRCU_NOTIFIER_INIT(name, name) 135 136 #endif 137 138 #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__ 145 146 extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh, 147 struct notifier_block *nb); 148 extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh, 149 struct notifier_block *nb); 150 extern int raw_notifier_chain_register(struct raw_notifier_head *nh, 151 struct notifier_block *nb); 152 extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, 153 struct notifier_block *nb); 154 155 extern int atomic_notifier_chain_register_unique_prio( 156 struct atomic_notifier_head *nh, struct notifier_block *nb); 157 extern int blocking_notifier_chain_register_unique_prio( 158 struct blocking_notifier_head *nh, struct notifier_block *nb); 159 160 extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, 161 struct notifier_block *nb); 162 extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, 163 struct notifier_block *nb); 164 extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, 165 struct notifier_block *nb); 166 extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, 167 struct notifier_block *nb); 168 169 extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, 170 unsigned long val, void *v); 171 extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, 172 unsigned long val, void *v); 173 extern int raw_notifier_call_chain(struct raw_notifier_head *nh, 174 unsigned long val, void *v); 175 extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, 176 unsigned long val, void *v); 177 178 extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh, 179 unsigned long val_up, unsigned long val_down, void *v); 180 extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, 181 unsigned long val_up, unsigned long val_down, void *v); 182 183 extern 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). */ notifier_from_errno(int err)196 static 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. */ notifier_to_errno(int ret)205 static 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 chains 213 * 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 and 233 * 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 */ 239 240 extern struct blocking_notifier_head reboot_notifier_list; 241 242 #endif /* __KERNEL__ */ 243 #endif /* _LINUX_NOTIFIER_H */ 244