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