LXR linux/include/linux/notifier.h

   1/*
   2 *      Routines to manage notifier chains for passing status changes to any
   3 *      interested routines. We need this instead of hard coded call lists so
   4 *      that modules can poke their nose into the innards. The network devices
   5 *      needed them so here they are for the rest of you.
   6 *
   7 *                              Alan Cox <Alan.Cox@linux.org>
   8 */
   9 
  10#ifndef _LINUX_NOTIFIER_H
  11#define _LINUX_NOTIFIER_H
  12#include <linux/errno.h>
  13#include <linux/mutex.h>
  14#include <linux/rwsem.h>
  15#include <linux/srcu.h>
  16
  17/*
  18 * Notifier chains are of four types:
  19 *
  20 *      Atomic notifier chains: Chain callbacks run in interrupt/atomic
  21 *              context. Callouts are not allowed to block.
  22 *      Blocking notifier chains: Chain callbacks run in process context.
  23 *              Callouts are allowed to block.
  24 *      Raw notifier chains: There are no restrictions on callbacks,
  25 *              registration, or unregistration.  All locking and protection
  26 *              must be provided by the caller.
  27 *      SRCU notifier chains: A variant of blocking notifier chains, with
  28 *              the same restrictions.
  29 *
  30 * atomic_notifier_chain_register() may be called from an atomic context,
  31 * but blocking_notifier_chain_register() and srcu_notifier_chain_register()
  32 * must be called from a process context.  Ditto for the corresponding
  33 * _unregister() routines.
  34 *
  35 * atomic_notifier_chain_unregister(), blocking_notifier_chain_unregister(),
  36 * and srcu_notifier_chain_unregister() _must not_ be called from within
  37 * the call chain.
  38 *
  39 * SRCU notifier chains are an alternative form of blocking notifier chains.
  40 * They use SRCU (Sleepable Read-Copy Update) instead of rw-semaphores for
  41 * protection of the chain links.  This means there is _very_ low overhead
  42 * in srcu_notifier_call_chain(): no cache bounces and no memory barriers.
  43 * As compensation, srcu_notifier_chain_unregister() is rather expensive.
  44 * SRCU notifier chains should be used when the chain will be called very
  45 * often but notifier_blocks will seldom be removed.  Also, SRCU notifier
  46 * chains are slightly more difficult to use because they require special
  47 * runtime initialization.
  48 */
  49
  50struct notifier_block {
  51        int (*notifier_call)(struct notifier_block *, unsigned long, void *);
  52        struct notifier_block *next;
  53        int priority;
  54};
  55
  56struct atomic_notifier_head {
  57        spinlock_t lock;
  58        struct notifier_block *head;
  59};
  60
  61struct blocking_notifier_head {
  62        struct rw_semaphore rwsem;
  63        struct notifier_block *head;
  64};
  65
  66struct raw_notifier_head {
  67        struct notifier_block *head;
  68};
  69
  70struct srcu_notifier_head {
  71        struct mutex mutex;
  72        struct srcu_struct srcu;
  73        struct notifier_block *head;
  74};
  75
  76#define ATOMIC_INIT_NOTIFIER_HEAD(name) do {    \
  77                spin_lock_init(&(name)->lock);  \
  78                (name)->head = NULL;            \
  79        } while (0)
  80#define BLOCKING_INIT_NOTIFIER_HEAD(name) do {  \
  81                init_rwsem(&(name)->rwsem);     \
  82                (name)->head = NULL;            \
  83        } while (0)
  84#define RAW_INIT_NOTIFIER_HEAD(name) do {       \
  85                (name)->head = NULL;            \
  86        } while (0)
  87
  88/* srcu_notifier_heads must be initialized and cleaned up dynamically */
  89extern void srcu_init_notifier_head(struct srcu_notifier_head *nh);
  90#define srcu_cleanup_notifier_head(name)        \
  91                cleanup_srcu_struct(&(name)->srcu);
  92
  93#define ATOMIC_NOTIFIER_INIT(name) {                            \
  94                .lock = __SPIN_LOCK_UNLOCKED(name.lock),        \
  95                .head = NULL }
  96#define BLOCKING_NOTIFIER_INIT(name) {                          \
  97                .rwsem = __RWSEM_INITIALIZER((name).rwsem),     \
  98                .head = NULL }
  99#define RAW_NOTIFIER_INIT(name) {                               \
 100                .head = NULL }
 101/* srcu_notifier_heads cannot be initialized statically */
 102
 103#define ATOMIC_NOTIFIER_HEAD(name)                              \
 104        struct atomic_notifier_head name =                      \
 105                ATOMIC_NOTIFIER_INIT(name)
 106#define BLOCKING_NOTIFIER_HEAD(name)                            \
 107        struct blocking_notifier_head name =                    \
 108                BLOCKING_NOTIFIER_INIT(name)
 109#define RAW_NOTIFIER_HEAD(name)                                 \
 110        struct raw_notifier_head name =                         \
 111                RAW_NOTIFIER_INIT(name)
 112
 113#ifdef __KERNEL__
 114
 115extern int atomic_notifier_chain_register(struct atomic_notifier_head *nh,
 116                struct notifier_block *nb);
 117extern int blocking_notifier_chain_register(struct blocking_notifier_head *nh,
 118                struct notifier_block *nb);
 119extern int raw_notifier_chain_register(struct raw_notifier_head *nh,
 120                struct notifier_block *nb);
 121extern int srcu_notifier_chain_register(struct srcu_notifier_head *nh,
 122                struct notifier_block *nb);
 123
 124extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *nh,
 125                struct notifier_block *nb);
 126extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *nh,
 127                struct notifier_block *nb);
 128extern int raw_notifier_chain_unregister(struct raw_notifier_head *nh,
 129                struct notifier_block *nb);
 130extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *nh,
 131                struct notifier_block *nb);
 132
 133extern int atomic_notifier_call_chain(struct atomic_notifier_head *nh,
 134                unsigned long val, void *v);
 135extern int __atomic_notifier_call_chain(struct atomic_notifier_head *nh,
 136        unsigned long val, void *v, int nr_to_call, int *nr_calls);
 137extern int blocking_notifier_call_chain(struct blocking_notifier_head *nh,
 138                unsigned long val, void *v);
 139extern int __blocking_notifier_call_chain(struct blocking_notifier_head *nh,
 140        unsigned long val, void *v, int nr_to_call, int *nr_calls);
 141extern int raw_notifier_call_chain(struct raw_notifier_head *nh,
 142                unsigned long val, void *v);
 143extern int __raw_notifier_call_chain(struct raw_notifier_head *nh,
 144        unsigned long val, void *v, int nr_to_call, int *nr_calls);
 145extern int srcu_notifier_call_chain(struct srcu_notifier_head *nh,
 146                unsigned long val, void *v);
 147extern int __srcu_notifier_call_chain(struct srcu_notifier_head *nh,
 148        unsigned long val, void *v, int nr_to_call, int *nr_calls);
 149
 150#define NOTIFY_DONE             0x0000          /* Don't care */
 151#define NOTIFY_OK               0x0001          /* Suits me */
 152#define NOTIFY_STOP_MASK        0x8000          /* Don't call further */
 153#define NOTIFY_BAD              (NOTIFY_STOP_MASK|0x0002)
 154                                                /* Bad/Veto action */
 155/*
 156 * Clean way to return from the notifier and stop further calls.
 157 */
 158#define NOTIFY_STOP             (NOTIFY_OK|NOTIFY_STOP_MASK)
 159
 160/* Encapsulate (negative) errno value (in particular, NOTIFY_BAD <=> EPERM). */
 161static inline int notifier_from_errno(int err)
 162{
 163        return NOTIFY_STOP_MASK | (NOTIFY_OK - err);
 164}
 165
 166/* Restore (negative) errno value from notify return value. */
 167static inline int notifier_to_errno(int ret)
 168{
 169        ret &= ~NOTIFY_STOP_MASK;
 170        return ret > NOTIFY_OK ? NOTIFY_OK - ret : 0;
 171}
 172
 173/*
 174 *      Declared notifiers so far. I can imagine quite a few more chains
 175 *      over time (eg laptop power reset chains, reboot chain (to clean 
 176 *      device units up), device [un]mount chain, module load/unload chain,
 177 *      low memory chain, screenblank chain (for plug in modular screenblankers) 
 178 *      VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
 179 */
 180 
 181/* netdevice notifier chain */
 182#define NETDEV_UP       0x0001  /* For now you can't veto a device up/down */
 183#define NETDEV_DOWN     0x0002
 184#define NETDEV_REBOOT   0x0003  /* Tell a protocol stack a network interface
 185                                   detected a hardware crash and restarted
 186                                   - we can use this eg to kick tcp sessions
 187                                   once done */
 188#define NETDEV_CHANGE   0x0004  /* Notify device state change */
 189#define NETDEV_REGISTER 0x0005
 190#define NETDEV_UNREGISTER       0x0006
 191#define NETDEV_CHANGEMTU        0x0007
 192#define NETDEV_CHANGEADDR       0x0008
 193#define NETDEV_GOING_DOWN       0x0009
 194#define NETDEV_CHANGENAME       0x000A
 195#define NETDEV_FEAT_CHANGE      0x000B
 196
 197#define SYS_DOWN        0x0001  /* Notify of system down */
 198#define SYS_RESTART     SYS_DOWN
 199#define SYS_HALT        0x0002  /* Notify of system halt */
 200#define SYS_POWER_OFF   0x0003  /* Notify of system power off */
 201
 202#define NETLINK_URELEASE        0x0001  /* Unicast netlink socket released */
 203
 204#define CPU_ONLINE              0x0002 /* CPU (unsigned)v is up */
 205#define CPU_UP_PREPARE          0x0003 /* CPU (unsigned)v coming up */
 206#define CPU_UP_CANCELED         0x0004 /* CPU (unsigned)v NOT coming up */
 207#define CPU_DOWN_PREPARE        0x0005 /* CPU (unsigned)v going down */
 208#define CPU_DOWN_FAILED         0x0006 /* CPU (unsigned)v NOT going down */
 209#define CPU_DEAD                0x0007 /* CPU (unsigned)v dead */
 210#define CPU_DYING               0x0008 /* CPU (unsigned)v not running any task,
 211                                        * not handling interrupts, soon dead */
 212
 213/* Used for CPU hotplug events occuring while tasks are frozen due to a suspend
 214 * operation in progress
 215 */
 216#define CPU_TASKS_FROZEN        0x0010
 217
 218#define CPU_ONLINE_FROZEN       (CPU_ONLINE | CPU_TASKS_FROZEN)
 219#define CPU_UP_PREPARE_FROZEN   (CPU_UP_PREPARE | CPU_TASKS_FROZEN)
 220#define CPU_UP_CANCELED_FROZEN  (CPU_UP_CANCELED | CPU_TASKS_FROZEN)
 221#define CPU_DOWN_PREPARE_FROZEN (CPU_DOWN_PREPARE | CPU_TASKS_FROZEN)
 222#define CPU_DOWN_FAILED_FROZEN  (CPU_DOWN_FAILED | CPU_TASKS_FROZEN)
 223#define CPU_DEAD_FROZEN         (CPU_DEAD | CPU_TASKS_FROZEN)
 224#define CPU_DYING_FROZEN        (CPU_DYING | CPU_TASKS_FROZEN)
 225
 226/* Hibernation and suspend events */
 227#define PM_HIBERNATION_PREPARE  0x0001 /* Going to hibernate */
 228#define PM_POST_HIBERNATION     0x0002 /* Hibernation finished */
 229#define PM_SUSPEND_PREPARE      0x0003 /* Going to suspend the system */
 230#define PM_POST_SUSPEND         0x0004 /* Suspend finished */
 231#define PM_RESTORE_PREPARE      0x0005 /* Going to restore a saved image */
 232#define PM_POST_RESTORE         0x0006 /* Restore failed */
 233
 234/* Console keyboard events.
 235 * Note: KBD_KEYCODE is always sent before KBD_UNBOUND_KEYCODE, KBD_UNICODE and
 236 * KBD_KEYSYM. */
 237#define KBD_KEYCODE             0x0001 /* Keyboard keycode, called before any other */
 238#define KBD_UNBOUND_KEYCODE     0x0002 /* Keyboard keycode which is not bound to any other */
 239#define KBD_UNICODE             0x0003 /* Keyboard unicode */
 240#define KBD_KEYSYM              0x0004 /* Keyboard keysym */
 241#define KBD_POST_KEYSYM         0x0005 /* Called after keyboard keysym interpretation */
 242
 243extern struct blocking_notifier_head reboot_notifier_list;
 244
 245/* Virtual Terminal events. */
 246#define VT_ALLOCATE             0x0001 /* Console got allocated */
 247#define VT_DEALLOCATE           0x0002 /* Console will be deallocated */
 248#define VT_WRITE                0x0003 /* A char got output */
 249#define VT_UPDATE               0x0004 /* A bigger update occurred */
 250
 251#endif /* __KERNEL__ */
 252#endif /* _LINUX_NOTIFIER_H */
 253