linux/include/linux/lglock.h
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   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
  37#ifdef CONFIG_DEBUG_LOCK_ALLOC
  38#define LOCKDEP_INIT_MAP lockdep_init_map
  39
  40#define DEFINE_LGLOCK_LOCKDEP(name)                                     \
  41 struct lock_class_key name##_lock_key;                                 \
  42 struct lockdep_map name##_lock_dep_map;                                \
  43 EXPORT_SYMBOL(name##_lock_dep_map)
  44
  45#else
  46#define LOCKDEP_INIT_MAP(a, b, c, d)
  47
  48#define DEFINE_LGLOCK_LOCKDEP(name)
  49#endif
  50
  51struct lglock {
  52        arch_spinlock_t __percpu *lock;
  53#ifdef CONFIG_DEBUG_LOCK_ALLOC
  54        struct lock_class_key lock_key;
  55        struct lockdep_map    lock_dep_map;
  56#endif
  57};
  58
  59#define DEFINE_LGLOCK(name)                                             \
  60        DEFINE_LGLOCK_LOCKDEP(name);                                    \
  61        DEFINE_PER_CPU(arch_spinlock_t, name ## _lock)                  \
  62        = __ARCH_SPIN_LOCK_UNLOCKED;                                    \
  63        struct lglock name = { .lock = &name ## _lock }
  64
  65void lg_lock_init(struct lglock *lg, char *name);
  66void lg_local_lock(struct lglock *lg);
  67void lg_local_unlock(struct lglock *lg);
  68void lg_local_lock_cpu(struct lglock *lg, int cpu);
  69void lg_local_unlock_cpu(struct lglock *lg, int cpu);
  70void lg_global_lock(struct lglock *lg);
  71void lg_global_unlock(struct lglock *lg);
  72
  73#endif
  74
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