forked from mirrors/linux
64b47e8fdb
When the system has only one CPU, lglock is effectively a spinlock; map it directly to spinlock to eliminate the indirection and duplicate code. In addition to removing overhead, this drops 1.6k of code with a defconfig modified to have !CONFIG_SMP, and 1.1k with a minimal config. Signed-off-by: Josh Triplett <josh@joshtriplett.org> Cc: Rusty Russell <rusty@rustcorp.com.au> Cc: Michal Marek <mmarek@suse.cz> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: David Howells <dhowells@redhat.com> Cc: "H. Peter Anvin" <hpa@zytor.com> Cc: Nick Piggin <npiggin@kernel.dk> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
76 lines
2.4 KiB
C
76 lines
2.4 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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#ifdef CONFIG_SMP
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#ifdef CONFIG_DEBUG_LOCK_ALLOC
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#define LOCKDEP_INIT_MAP lockdep_init_map
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#else
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#define LOCKDEP_INIT_MAP(a, b, c, d)
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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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static 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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#define DEFINE_STATIC_LGLOCK(name) \
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static DEFINE_PER_CPU(arch_spinlock_t, name ## _lock) \
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= __ARCH_SPIN_LOCK_UNLOCKED; \
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static 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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#else
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/* When !CONFIG_SMP, map lglock to spinlock */
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#define lglock spinlock
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#define DEFINE_LGLOCK(name) DEFINE_SPINLOCK(name)
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#define DEFINE_STATIC_LGLOCK(name) static DEFINE_SPINLOCK(name)
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#define lg_lock_init(lg, name) spin_lock_init(lg)
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#define lg_local_lock spin_lock
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#define lg_local_unlock spin_unlock
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#define lg_local_lock_cpu(lg, cpu) spin_lock(lg)
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#define lg_local_unlock_cpu(lg, cpu) spin_unlock(lg)
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#define lg_global_lock spin_lock
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#define lg_global_unlock spin_unlock
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#endif
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#endif
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