Commit 64b47e8f authored by Josh Triplett's avatar Josh Triplett Committed by Linus Torvalds
Browse files

lglock: map to spinlock when !CONFIG_SMP 



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: default avatarJosh 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: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 188a8140

include/linux/lglock.h

+16 −0
Original line number Diff line number Diff line
@@ -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

kernel/locking/Makefile

+2 −1
Original line number Diff line number Diff line 


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

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