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 <[email protected]> 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 #ifdef CONFIG_TREE_SRCU 77 struct srcu_usage srcuu; 78 #endif 79 struct srcu_struct srcu; 80 struct notifier_block __rcu *head; 81 }; 82 83 #define ATOMIC_INIT_NOTIFIER_HEAD(name) do { \ 84 spin_lock_init(&(name)->lock); \ 85 (name)->head = NULL; \ 86 } while (0) 87 #define BLOCKING_INIT_NOTIFIER_HEAD(name) do { \ 88 init_rwsem(&(name)->rwsem); \ 89 (name)->head = NULL; \ 90 } while (0) 91 #define RAW_INIT_NOTIFIER_HEAD(name) do { \ 92 (name)->head = NULL; \ 93 } while (0) 94 95 /* srcu_notifier_heads must be cleaned up dynamically */ 96 extern void srcu_init_notifier_head(struct srcu_notifier_head *nh); 97 #define srcu_cleanup_notifier_head(name) \ 98 cleanup_srcu_struct(&(name)->srcu); 99 100 #define ATOMIC_NOTIFIER_INIT(name) { \ 101 .lock = __SPIN_LOCK_UNLOCKED(name.lock), \ 102 .head = NULL } 103 #define BLOCKING_NOTIFIER_INIT(name) { \ 104 .rwsem = __RWSEM_INITIALIZER((name).rwsem), \ 105 .head = NULL } 106 #define RAW_NOTIFIER_INIT(name) { \ 107 .head = NULL } 108 109 #define SRCU_NOTIFIER_INIT(name, pcpu) \ 110 { \ 111 .mutex = __MUTEX_INITIALIZER(name.mutex), \ 112 .head = NULL, \ 113 .srcu = __SRCU_STRUCT_INIT(name.srcu, name.srcuu, pcpu), \ 114 } 115 116 #define ATOMIC_NOTIFIER_HEAD(name) \ 117 struct atomic_notifier_head name = \ 118 ATOMIC_NOTIFIER_INIT(name) 119 #define BLOCKING_NOTIFIER_HEAD(name) \ 120 struct blocking_notifier_head name = \ 121 BLOCKING_NOTIFIER_INIT(name) 122 #define RAW_NOTIFIER_HEAD(name) \ 123 struct raw_notifier_head name = \ 124 RAW_NOTIFIER_INIT(name) 125 126 #ifdef CONFIG_TREE_SRCU 127 #define _SRCU_NOTIFIER_HEAD(name, mod) \ 128 static DEFINE_PER_CPU(struct srcu_data, name##_head_srcu_data); \ 129 mod struct srcu_notifier_head name = \ 130 SRCU_NOTIFIER_INIT(name, name##_head_srcu_data) 131 132 #else 133 #define _SRCU_NOTIFIER_HEAD(name, mod) \ 134 mod struct srcu_notifier_head name = \ 135 SRCU_NOTIFIER_INIT(name, name) 136 137 #endif 138 139 #define SRCU_NOTIFIER_HEAD(name) \ 140 _SRCU_NOTIFIER_HEAD(name, /* not static */) 141 142 #define SRCU_NOTIFIER_HEAD_STATIC(name) \ 143 _SRCU_NOTIFIER_HEAD(name, static) 144 145 #ifdef __KERNEL__ 146 147 extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh, 148 struct notifier_block *nb); 149 extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh, 150 struct notifier_block *nb); 151 extern int raw_notifier_chain_register(struct raw_notifier_head *nh, 152 struct notifier_block *nb); 153 extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh, 154 struct notifier_block *nb); 155 156 extern int atomic_notifier_chain_register_unique_prio( 157 struct atomic_notifier_head *nh, struct notifier_block *nb); 158 extern int blocking_notifier_chain_register_unique_prio( 159 struct blocking_notifier_head *nh, struct notifier_block *nb); 160 161 extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh, 162 struct notifier_block *nb); 163 extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh, 164 struct notifier_block *nb); 165 extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh, 166 struct notifier_block *nb); 167 extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh, 168 struct notifier_block *nb); 169 170 extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh, 171 unsigned long val, void *v); 172 extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh, 173 unsigned long val, void *v); 174 extern int raw_notifier_call_chain(struct raw_notifier_head *nh, 175 unsigned long val, void *v); 176 extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh, 177 unsigned long val, void *v); 178 179 extern int blocking_notifier_call_chain_robust(struct blocking_notifier_head *nh, 180 unsigned long val_up, unsigned long val_down, void *v); 181 extern int raw_notifier_call_chain_robust(struct raw_notifier_head *nh, 182 unsigned long val_up, unsigned long val_down, void *v); 183 184 extern bool atomic_notifier_call_chain_is_empty(struct atomic_notifier_head *nh); 185 186 #define NOTIFY_DONE 0x0000 /* Don't care */ 187 #define NOTIFY_OK 0x0001 /* Suits me */ 188 #define NOTIFY_STOP_MASK 0x8000 /* Don't call further */ 189 #define NOTIFY_BAD (NOTIFY_STOP_MASK|0x0002) 190 /* Bad/Veto action */ 191 /* 192 * Clean way to return from the notifier and stop further calls. 193 */ 194 #define NOTIFY_STOP (NOTIFY_OK|NOTIFY_STOP_MASK) 195 196 /* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */ 197 static inline int notifier_from_errno(int err) 198 { 199 if (err) 200 return NOTIFY_STOP_MASK | (NOTIFY_OK - err); 201 202 return NOTIFY_OK; 203 } 204 205 /* Restore (negative) errno value from notify return value. */ 206 static inline int notifier_to_errno(int ret) 207 { 208 ret &= ~NOTIFY_STOP_MASK; 209 return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0; 210 } 211 212 /* 213 * Declared notifiers so far. I can imagine quite a few more chains 214 * over time (eg laptop power reset chains, reboot chain (to clean 215 * device units up), device [un]mount chain, module load/unload chain, 216 * low memory chain, screenblank chain (for plug in modular screenblankers) 217 * VC switch chains (for loadable kernel svgalib VC switch helpers) etc... 218 */ 219 220 /* CPU notfiers are defined in include/linux/cpu.h. */ 221 222 /* netdevice notifiers are defined in include/linux/netdevice.h */ 223 224 /* reboot notifiers are defined in include/linux/reboot.h. */ 225 226 /* Hibernation and suspend events are defined in include/linux/suspend.h. */ 227 228 /* Virtual Terminal events are defined in include/linux/vt.h. */ 229 230 #define NETLINK_URELEASE 0x0001 /* Unicast netlink socket released */ 231 232 /* Console keyboard events. 233 * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and 234 * KBD_KEYSYM. */ 235 #define KBD_KEYCODE 0x0001 /* Keyboard keycode, called before any other */ 236 #define KBD_UNBOUND_KEYCODE 0x0002 /* Keyboard keycode which is not bound to any other */ 237 #define KBD_UNICODE 0x0003 /* Keyboard unicode */ 238 #define KBD_KEYSYM 0x0004 /* Keyboard keysym */ 239 #define KBD_POST_KEYSYM 0x0005 /* Called after keyboard keysym interpretation */ 240 241 extern struct blocking_notifier_head reboot_notifier_list; 242 243 #endif /* __KERNEL__ */ 244 #endif /* _LINUX_NOTIFIER_H */ 245