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#ifdef CONFIG_SMP
  29
  30#ifdef CONFIG_DEBUG_LOCK_ALLOC
  31#define LOCKDEP_INIT_MAP lockdep_init_map
  32#else
  33#define LOCKDEP_INIT_MAP(a, b, c, d)
  34#endif
  35
  36struct lglock {
  37        arch_spinlock_t __percpu *lock;
  38#ifdef CONFIG_DEBUG_LOCK_ALLOC
  39        struct lock_class_key lock_key;
  40        struct lockdep_map    lock_dep_map;
  41#endif
  42};
  43
  44#define DEFINE_LGLOCK(name)                                             \
  45        static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock)           \
  46        = __ARCH_SPIN_LOCK_UNLOCKED;                                    \
  47        struct lglock name = { .lock = &name ## _lock }
  48
  49#define DEFINE_STATIC_LGLOCK(name)                                      \
  50        static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock)           \
  51        = __ARCH_SPIN_LOCK_UNLOCKED;                                    \
  52        static struct lglock name = { .lock = &name ## _lock }
  53
  54void lg_lock_init(struct lglock *lg, char *name);
  55void lg_local_lock(struct lglock *lg);
  56void lg_local_unlock(struct lglock *lg);
  57void lg_local_lock_cpu(struct lglock *lg, int cpu);
  58void lg_local_unlock_cpu(struct lglock *lg, int cpu);
  59void lg_global_lock(struct lglock *lg);
  60void lg_global_unlock(struct lglock *lg);
  61
  62#else
  63/* When !CONFIG_SMP, map lglock to spinlock */
  64#define lglock spinlock
  65#define DEFINE_LGLOCK(name) DEFINE_SPINLOCK(name)
  66#define DEFINE_STATIC_LGLOCK(name) static DEFINE_SPINLOCK(name)
  67#define lg_lock_init(lg, name) spin_lock_init(lg)
  68#define lg_local_lock spin_lock
  69#define lg_local_unlock spin_unlock
  70#define lg_local_lock_cpu(lg, cpu) spin_lock(lg)
  71#define lg_local_unlock_cpu(lg, cpu) spin_unlock(lg)
  72#define lg_global_lock spin_lock
  73#define lg_global_unlock spin_unlock
  74#endif
  75
  76#endif
  77