root/include/linux/notifier.h

INCLUDED FROM

DEFINITIONS

1. notifier_from_errno
2. notifier_to_errno

   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). */
 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. */
 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 */