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authorJosh Triplett <josh@joshtriplett.org>2014-04-08 02:39:45 +0400
committerLinus Torvalds <torvalds@linux-foundation.org>2014-04-08 03:36:14 +0400
commit64b47e8fdb40a0d46e8cf458dd3e24f8afa073f6 (patch)
tree284e2335ba622406f3d3437c2abd416cc8979294
parent188a81409ff7de1c5aae947a96356ddd8ff4aaa3 (diff)
downloadlinux-64b47e8fdb40a0d46e8cf458dd3e24f8afa073f6.tar.xz
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: 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>
-rw-r--r--include/linux/lglock.h16
-rw-r--r--kernel/locking/Makefile3
2 files changed, 18 insertions, 1 deletions
diff --git a/include/linux/lglock.h b/include/linux/lglock.h
index 96549abe8842..0081f000e34b 100644
--- a/include/linux/lglock.h
+++ b/include/linux/lglock.h
@@ -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
diff --git a/kernel/locking/Makefile b/kernel/locking/Makefile
index 306a76b51e0f..b8bdcd4785b7 100644
--- a/kernel/locking/Makefile
+++ b/kernel/locking/Makefile
@@ -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