lglock: introduce special lglock and brlock spin locks
lglock: introduce special lglock and brlock spin locks This patch introduces "local-global" locks (lglocks). These 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. Thanks to Paul for local/global naming convention. Cc: linux-kernel@vger.kernel.org Cc: Al Viro <viro@ZenIV.linux.org.uk> Cc: "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> Signed-off-by: Nick Piggin <npiggin@kernel.dk> Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Nick Piggin
Al Viro
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172
include/linux/lglock.h
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172
include/linux/lglock.h
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/*
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* Specialised local-global spinlock. Can only be declared as global variables
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* to avoid overhead and keep things simple (and we don't want to start using
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* these inside dynamically allocated structures).
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*
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* "local/global locks" (lglocks) can be used to:
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*
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* - Provide fast exclusive access to per-CPU data, with exclusive access to
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* another CPU's data allowed but possibly subject to contention, and to
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* provide very slow exclusive access to all per-CPU data.
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* - Or to provide very fast and scalable read serialisation, and to provide
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* very slow exclusive serialisation of data (not necessarily per-CPU data).
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*
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* Brlocks are also implemented as a short-hand notation for the latter use
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* case.
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*
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* Copyright 2009, 2010, Nick Piggin, Novell Inc.
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*/
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#ifndef __LINUX_LGLOCK_H
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#define __LINUX_LGLOCK_H
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#include <linux/spinlock.h>
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#include <linux/lockdep.h>
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#include <linux/percpu.h>
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/* can make br locks by using local lock for read side, global lock for write */
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#define br_lock_init(name) name##_lock_init()
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#define br_read_lock(name) name##_local_lock()
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#define br_read_unlock(name) name##_local_unlock()
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#define br_write_lock(name) name##_global_lock_online()
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#define br_write_unlock(name) name##_global_unlock_online()
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#define DECLARE_BRLOCK(name) DECLARE_LGLOCK(name)
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#define DEFINE_BRLOCK(name) DEFINE_LGLOCK(name)
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#define lg_lock_init(name) name##_lock_init()
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#define lg_local_lock(name) name##_local_lock()
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#define lg_local_unlock(name) name##_local_unlock()
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#define lg_local_lock_cpu(name, cpu) name##_local_lock_cpu(cpu)
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#define lg_local_unlock_cpu(name, cpu) name##_local_unlock_cpu(cpu)
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#define lg_global_lock(name) name##_global_lock()
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#define lg_global_unlock(name) name##_global_unlock()
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#define lg_global_lock_online(name) name##_global_lock_online()
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#define lg_global_unlock_online(name) name##_global_unlock_online()
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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#define LOCKDEP_INIT_MAP lockdep_init_map
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#define DEFINE_LGLOCK_LOCKDEP(name) \
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struct lock_class_key name##_lock_key; \
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struct lockdep_map name##_lock_dep_map; \
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EXPORT_SYMBOL(name##_lock_dep_map)
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#else
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#define LOCKDEP_INIT_MAP(a, b, c, d)
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#define DEFINE_LGLOCK_LOCKDEP(name)
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#endif
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#define DECLARE_LGLOCK(name) \
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extern void name##_lock_init(void); \
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extern void name##_local_lock(void); \
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extern void name##_local_unlock(void); \
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extern void name##_local_lock_cpu(int cpu); \
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extern void name##_local_unlock_cpu(int cpu); \
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extern void name##_global_lock(void); \
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extern void name##_global_unlock(void); \
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extern void name##_global_lock_online(void); \
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extern void name##_global_unlock_online(void); \
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#define DEFINE_LGLOCK(name) \
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\
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DEFINE_PER_CPU(arch_spinlock_t, name##_lock); \
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DEFINE_LGLOCK_LOCKDEP(name); \
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\
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void name##_lock_init(void) { \
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int i; \
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LOCKDEP_INIT_MAP(&name##_lock_dep_map, #name, &name##_lock_key, 0); \
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for_each_possible_cpu(i) { \
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arch_spinlock_t *lock; \
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lock = &per_cpu(name##_lock, i); \
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*lock = (arch_spinlock_t)__ARCH_SPIN_LOCK_UNLOCKED; \
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} \
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} \
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EXPORT_SYMBOL(name##_lock_init); \
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\
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void name##_local_lock(void) { \
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arch_spinlock_t *lock; \
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preempt_disable(); \
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rwlock_acquire_read(&name##_lock_dep_map, 0, 0, _THIS_IP_); \
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lock = &__get_cpu_var(name##_lock); \
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arch_spin_lock(lock); \
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} \
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EXPORT_SYMBOL(name##_local_lock); \
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\
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void name##_local_unlock(void) { \
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arch_spinlock_t *lock; \
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rwlock_release(&name##_lock_dep_map, 1, _THIS_IP_); \
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lock = &__get_cpu_var(name##_lock); \
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arch_spin_unlock(lock); \
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preempt_enable(); \
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} \
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EXPORT_SYMBOL(name##_local_unlock); \
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\
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void name##_local_lock_cpu(int cpu) { \
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arch_spinlock_t *lock; \
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preempt_disable(); \
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rwlock_acquire_read(&name##_lock_dep_map, 0, 0, _THIS_IP_); \
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lock = &per_cpu(name##_lock, cpu); \
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arch_spin_lock(lock); \
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} \
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EXPORT_SYMBOL(name##_local_lock_cpu); \
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\
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void name##_local_unlock_cpu(int cpu) { \
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arch_spinlock_t *lock; \
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rwlock_release(&name##_lock_dep_map, 1, _THIS_IP_); \
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lock = &per_cpu(name##_lock, cpu); \
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arch_spin_unlock(lock); \
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preempt_enable(); \
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} \
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EXPORT_SYMBOL(name##_local_unlock_cpu); \
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\
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void name##_global_lock_online(void) { \
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int i; \
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preempt_disable(); \
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rwlock_acquire(&name##_lock_dep_map, 0, 0, _RET_IP_); \
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for_each_online_cpu(i) { \
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arch_spinlock_t *lock; \
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lock = &per_cpu(name##_lock, i); \
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arch_spin_lock(lock); \
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} \
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} \
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EXPORT_SYMBOL(name##_global_lock_online); \
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\
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void name##_global_unlock_online(void) { \
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int i; \
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rwlock_release(&name##_lock_dep_map, 1, _RET_IP_); \
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for_each_online_cpu(i) { \
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arch_spinlock_t *lock; \
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lock = &per_cpu(name##_lock, i); \
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arch_spin_unlock(lock); \
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} \
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preempt_enable(); \
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} \
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EXPORT_SYMBOL(name##_global_unlock_online); \
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\
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void name##_global_lock(void) { \
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int i; \
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preempt_disable(); \
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rwlock_acquire(&name##_lock_dep_map, 0, 0, _RET_IP_); \
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for_each_online_cpu(i) { \
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arch_spinlock_t *lock; \
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lock = &per_cpu(name##_lock, i); \
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arch_spin_lock(lock); \
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} \
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} \
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EXPORT_SYMBOL(name##_global_lock); \
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\
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void name##_global_unlock(void) { \
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int i; \
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rwlock_release(&name##_lock_dep_map, 1, _RET_IP_); \
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for_each_online_cpu(i) { \
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arch_spinlock_t *lock; \
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lock = &per_cpu(name##_lock, i); \
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arch_spin_unlock(lock); \
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} \
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preempt_enable(); \
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} \
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EXPORT_SYMBOL(name##_global_unlock);
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#endif
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