74 lines
2.3 KiB
C
74 lines
2.3 KiB
C
/*
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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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#include <linux/cpu.h>
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#include <linux/notifier.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) lg_lock_init(name, #name)
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#define br_read_lock(name) lg_local_lock(name)
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#define br_read_unlock(name) lg_local_unlock(name)
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#define br_write_lock(name) lg_global_lock(name)
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#define br_write_unlock(name) lg_global_unlock(name)
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#define DEFINE_BRLOCK(name) DEFINE_LGLOCK(name)
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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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struct lglock {
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arch_spinlock_t __percpu *lock;
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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struct lock_class_key lock_key;
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struct lockdep_map lock_dep_map;
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#endif
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};
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#define DEFINE_LGLOCK(name) \
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DEFINE_LGLOCK_LOCKDEP(name); \
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DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \
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= __ARCH_SPIN_LOCK_UNLOCKED; \
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struct lglock name = { .lock = &name ## _lock }
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void lg_lock_init(struct lglock *lg, char *name);
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void lg_local_lock(struct lglock *lg);
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void lg_local_unlock(struct lglock *lg);
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void lg_local_lock_cpu(struct lglock *lg, int cpu);
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void lg_local_unlock_cpu(struct lglock *lg, int cpu);
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void lg_global_lock(struct lglock *lg);
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void lg_global_unlock(struct lglock *lg);
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#endif
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