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
  50 struct notifier_block {
  51         int (*notifier_call)(struct notifier_block *, unsigned long, void *);
  52         struct notifier_block *next;
  53         int priority;
  54 };
  55
  56 struct atomic_notifier_head {
  57         spinlock_t lock;
  58         struct notifier_block *head;
  59 };
  60
  61 struct blocking_notifier_head {
  62         struct rw_semaphore rwsem;
  63         struct notifier_block *head;
  64 };
  65
  66 struct raw_notifier_head {
  67         struct notifier_block *head;
  68 };
  69
  70 struct 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 */
  89 extern 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
 115 extern int atomic_notifier_chain_register(struct atomic_notifier_head *,
 116                 struct notifier_block *);
 117 extern int blocking_notifier_chain_register(struct blocking_notifier_head *,
 118                 struct notifier_block *);
 119 extern int raw_notifier_chain_register(struct raw_notifier_head *,
 120                 struct notifier_block *);
 121 extern int srcu_notifier_chain_register(struct srcu_notifier_head *,
 122                 struct notifier_block *);
 123
 124 extern int atomic_notifier_chain_unregister(struct atomic_notifier_head *,
 125                 struct notifier_block *);
 126 extern int blocking_notifier_chain_unregister(struct blocking_notifier_head *,
 127                 struct notifier_block *);
 128 extern int raw_notifier_chain_unregister(struct raw_notifier_head *,
 129                 struct notifier_block *);
 130 extern int srcu_notifier_chain_unregister(struct srcu_notifier_head *,
 131                 struct notifier_block *);
 132
 133 extern int atomic_notifier_call_chain(struct atomic_notifier_head *,
 134                 unsigned long val, void *v);
 135 extern int blocking_notifier_call_chain(struct blocking_notifier_head *,
 136                 unsigned long val, void *v);
 137 extern int raw_notifier_call_chain(struct raw_notifier_head *,
 138                 unsigned long val, void *v);
 139 extern int srcu_notifier_call_chain(struct srcu_notifier_head *,
 140                 unsigned long val, void *v);
 141
 142 #define NOTIFY_DONE             0x0000          /* Don't care */
 143 #define NOTIFY_OK               0x0001          /* Suits me */
 144 #define NOTIFY_STOP_MASK        0x8000          /* Don't call further */
 145 #define NOTIFY_BAD              (NOTIFY_STOP_MASK|0x0002)
 146                                                 /* Bad/Veto action */
 147 /*
 148  * Clean way to return from the notifier and stop further calls.
 149  */
 150 #define NOTIFY_STOP             (NOTIFY_OK|NOTIFY_STOP_MASK)
 151
 152 /*
 153  *      Declared notifiers so far. I can imagine quite a few more chains
 154  *      over time (eg laptop power reset chains, reboot chain (to clean
 155  *      device units up), device [un]mount chain, module load/unload chain,
 156  *      low memory chain, screenblank chain (for plug in modular screenblankers)
 157  *      VC switch chains (for loadable kernel svgalib VC switch helpers) etc...
 158  */
 159
 160 /* netdevice notifier chain */
 161 #define NETDEV_UP       0x0001  /* For now you can't veto a device up/down */
 162 #define NETDEV_DOWN     0x0002
 163 #define NETDEV_REBOOT   0x0003  /* Tell a protocol stack a network interface
 164                                    detected a hardware crash and restarted
 165                                    - we can use this eg to kick tcp sessions
 166                                    once done */
 167 #define NETDEV_CHANGE   0x0004  /* Notify device state change */
 168 #define NETDEV_REGISTER 0x0005
 169 #define NETDEV_UNREGISTER       0x0006
 170 #define NETDEV_CHANGEMTU        0x0007
 171 #define NETDEV_CHANGEADDR       0x0008
 172 #define NETDEV_GOING_DOWN       0x0009
 173 #define NETDEV_CHANGENAME       0x000A
 174 #define NETDEV_FEAT_CHANGE      0x000B
 175
 176 #define SYS_DOWN        0x0001  /* Notify of system down */
 177 #define SYS_RESTART     SYS_DOWN
 178 #define SYS_HALT        0x0002  /* Notify of system halt */
 179 #define SYS_POWER_OFF   0x0003  /* Notify of system power off */
 180
 181 #define NETLINK_URELEASE        0x0001  /* Unicast netlink socket released */
 182
 183 #define CPU_ONLINE              0x0002 /* CPU (unsigned)v is up */
 184 #define CPU_UP_PREPARE          0x0003 /* CPU (unsigned)v coming up */
 185 #define CPU_UP_CANCELED         0x0004 /* CPU (unsigned)v NOT coming up */
 186 #define CPU_DOWN_PREPARE        0x0005 /* CPU (unsigned)v going down */
 187 #define CPU_DOWN_FAILED         0x0006 /* CPU (unsigned)v NOT going down */
 188 #define CPU_DEAD                0x0007 /* CPU (unsigned)v dead */
 189
 190 #endif /* __KERNEL__ */
 191 #endif /* _LINUX_NOTIFIER_H */