LXR linux/include/linux/lglock.h

   1/*
   2 * Specialised local-global spinlock. Can only be declared as global variables
   3 * to avoid overhead and keep things simple (and we don't want to start using
   4 * these inside dynamically allocated structures).
   5 *
   6 * "local/global locks" (lglocks) can be used to:
   7 *
   8 * - Provide fast exclusive access to per-CPU data, with exclusive access to
   9 *   another CPU's data allowed but possibly subject to contention, and to
  10 *   provide very slow exclusive access to all per-CPU data.
  11 * - Or to provide very fast and scalable read serialisation, and to provide
  12 *   very slow exclusive serialisation of data (not necessarily per-CPU data).
  13 *
  14 * Brlocks are also implemented as a short-hand notation for the latter use
  15 * case.
  16 *
  17 * Copyright 2009, 2010, Nick Piggin, Novell Inc.
  18 */
  19#ifndef __LINUX_LGLOCK_H
  20#define __LINUX_LGLOCK_H
  21
  22#include <linux/spinlock.h>
  23#include <linux/lockdep.h>
  24#include <linux/percpu.h>
  25#include <linux/cpu.h>
  26#include <linux/notifier.h>
  27
  28/* can make br locks by using local lock for read side, global lock for write */
  29#define br_lock_init(name)      lg_lock_init(name, #name)
  30#define br_read_lock(name)      lg_local_lock(name)
  31#define br_read_unlock(name)    lg_local_unlock(name)
  32#define br_write_lock(name)     lg_global_lock(name)
  33#define br_write_unlock(name)   lg_global_unlock(name)
  34
  35#define DEFINE_BRLOCK(name)             DEFINE_LGLOCK(name)
  36#define DEFINE_STATIC_BRLOCK(name)      DEFINE_STATIC_LGLOCK(name)
  37
  38#ifdef CONFIG_DEBUG_LOCK_ALLOC
  39#define LOCKDEP_INIT_MAP lockdep_init_map
  40#else
  41#define LOCKDEP_INIT_MAP(a, b, c, d)
  42#endif
  43
  44struct lglock {
  45        arch_spinlock_t __percpu *lock;
  46#ifdef CONFIG_DEBUG_LOCK_ALLOC
  47        struct lock_class_key lock_key;
  48        struct lockdep_map    lock_dep_map;
  49#endif
  50};
  51
  52#define DEFINE_LGLOCK(name)                                             \
  53        static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock)           \
  54        = __ARCH_SPIN_LOCK_UNLOCKED;                                    \
  55        struct lglock name = { .lock = &name ## _lock }
  56
  57#define DEFINE_STATIC_LGLOCK(name)                                      \
  58        static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock)           \
  59        = __ARCH_SPIN_LOCK_UNLOCKED;                                    \
  60        static struct lglock name = { .lock = &name ## _lock }
  61
  62void lg_lock_init(struct lglock *lg, char *name);
  63
  64void lg_local_lock(struct lglock *lg);
  65void lg_local_unlock(struct lglock *lg);
  66void lg_local_lock_cpu(struct lglock *lg, int cpu);
  67void lg_local_unlock_cpu(struct lglock *lg, int cpu);
  68
  69void lg_double_lock(struct lglock *lg, int cpu1, int cpu2);
  70void lg_double_unlock(struct lglock *lg, int cpu1, int cpu2);
  71
  72void lg_global_lock(struct lglock *lg);
  73void lg_global_unlock(struct lglock *lg);
  74
  75#endif
  76