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/*
* Specialised local-global spinlock. Can only be declared as global variables
* to avoid overhead and keep things simple (and we don't want to start using
* these inside dynamically allocated structures).
*
* "local/global locks" (lglocks) can be used to:
*
* - Provide fast exclusive access to per-CPU data, with exclusive access to
* another CPU's data allowed but possibly subject to contention, and to
* provide very slow exclusive access to all per-CPU data.
* - Or to provide very fast and scalable read serialisation, and to provide
* very slow exclusive serialisation of data (not necessarily per-CPU data).
*
* Brlocks are also implemented as a short-hand notation for the latter use
* case.
*
* Copyright 2009, 2010, Nick Piggin, Novell Inc.
*/
#ifndef __LINUX_LGLOCK_H
#define __LINUX_LGLOCK_H
#include <linux/spinlock.h>
#include <linux/lockdep.h>
#include <linux/percpu.h>
#include <linux/cpu.h>
#include <linux/notifier.h>
/* can make br locks by using local lock for read side, global lock for write */
#define br_lock_init(name) lg_lock_init(name, #name)
#define br_read_lock(name) lg_local_lock(name)
#define br_read_unlock(name) lg_local_unlock(name)
#define br_write_lock(name) lg_global_lock(name)
#define br_write_unlock(name) lg_global_unlock(name)
#define DEFINE_BRLOCK(name) DEFINE_LGLOCK(name)
#ifdef CONFIG_DEBUG_LOCK_ALLOC
#define LOCKDEP_INIT_MAP lockdep_init_map
#define DEFINE_LGLOCK_LOCKDEP(name) \
struct lock_class_key name##_lock_key; \
struct lockdep_map name##_lock_dep_map; \
EXPORT_SYMBOL(name##_lock_dep_map)
#else
#define LOCKDEP_INIT_MAP(a, b, c, d)
#define DEFINE_LGLOCK_LOCKDEP(name)
#endif
struct lglock {
arch_spinlock_t __percpu *lock;
#ifdef CONFIG_DEBUG_LOCK_ALLOC
struct lock_class_key lock_key;
struct lockdep_map lock_dep_map;
#endif
};
#define DEFINE_LGLOCK(name) \
DEFINE_LGLOCK_LOCKDEP(name); \
DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \
= __ARCH_SPIN_LOCK_UNLOCKED; \
struct lglock name = { .lock = &name ## _lock }
void lg_lock_init(struct lglock *lg, char *name);
void lg_local_lock(struct lglock *lg);
void lg_local_unlock(struct lglock *lg);
void lg_local_lock_cpu(struct lglock *lg, int cpu);
void lg_local_unlock_cpu(struct lglock *lg, int cpu);
void lg_global_lock(struct lglock *lg);
void lg_global_unlock(struct lglock *lg);
#endif
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