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lglock: map to spinlock when !CONFIG_SMP

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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>
This commit is contained in:
Josh Triplett 2014-04-07 15:39:45 -07:00 committed by Linus Torvalds
parent 188a81409f
commit 64b47e8fdb
2 changed files with 18 additions and 1 deletions
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16
include/linux/lglock.h
View File

@ -25,6 +25,8 @@
#include <linux/cpu.h>
#include <linux/notifier.h>
#ifdef CONFIG_SMP
#ifdef CONFIG_DEBUG_LOCK_ALLOC
#define LOCKDEP_INIT_MAP lockdep_init_map
#else
@ -57,4 +59,18 @@ void lg_local_unlock_cpu(struct lglock *lg, int cpu);
void lg_global_lock(struct lglock *lg);
void lg_global_unlock(struct lglock *lg);
#else
/* When !CONFIG_SMP, map lglock to spinlock */
#define lglock spinlock
#define DEFINE_LGLOCK(name) DEFINE_SPINLOCK(name)
#define DEFINE_STATIC_LGLOCK(name) static DEFINE_SPINLOCK(name)
#define lg_lock_init(lg, name) spin_lock_init(lg)
#define lg_local_lock spin_lock
#define lg_local_unlock spin_unlock
#define lg_local_lock_cpu(lg, cpu) spin_lock(lg)
#define lg_local_unlock_cpu(lg, cpu) spin_unlock(lg)
#define lg_global_lock spin_lock
#define lg_global_unlock spin_unlock
#endif
#endif

3
kernel/locking/Makefile
View File

@ -1,5 +1,5 @@
obj-y += mutex.o semaphore.o rwsem.o lglock.o mcs_spinlock.o
obj-y += mutex.o semaphore.o rwsem.o mcs_spinlock.o
ifdef CONFIG_FUNCTION_TRACER
CFLAGS_REMOVE_lockdep.o = -pg
@ -14,6 +14,7 @@ ifeq ($(CONFIG_PROC_FS),y)
obj-$(CONFIG_LOCKDEP) += lockdep_proc.o
endif
obj-$(CONFIG_SMP) += spinlock.o
obj-$(CONFIG_SMP) += lglock.o
obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
obj-$(CONFIG_RT_MUTEXES) += rtmutex.o
obj-$(CONFIG_DEBUG_RT_MUTEXES) += rtmutex-debug.o