Subject: + lglock-map-to-spinlock-when-config_smp.patch added to -mm tree
To: josh@xxxxxxxxxxxxxxxx,dhowells@xxxxxxxxxx,hpa@xxxxxxxxx,mmarek@xxxxxxx,npiggin@xxxxxxxxx,rusty@xxxxxxxxxxxxxxx,tglx@xxxxxxxxxxxxx
From: akpm@xxxxxxxxxxxxxxxxxxxx
Date: Fri, 01 Nov 2013 15:33:06 -0700
The patch titled
Subject: lglock: map to spinlock when !CONFIG_SMP
has been added to the -mm tree. Its filename is
lglock-map-to-spinlock-when-config_smp.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/lglock-map-to-spinlock-when-config_smp.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/lglock-map-to-spinlock-when-config_smp.patch
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------------------------------------------------------
From: Josh Triplett <josh@xxxxxxxxxxxxxxxx>
Subject: 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@xxxxxxxxxxxxxxxx>
Cc: Rusty Russell <rusty@xxxxxxxxxxxxxxx>
Cc: Michal Marek <mmarek@xxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: David Howells <dhowells@xxxxxxxxxx>
Cc: "H. Peter Anvin" <hpa@xxxxxxxxx>
Cc: Nick Piggin <npiggin@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/lglock.h | 16 ++++++++++++++++
kernel/Makefile | 4 ++--
2 files changed, 18 insertions(+), 2 deletions(-)
diff -puN include/linux/lglock.h~lglock-map-to-spinlock-when-config_smp include/linux/lglock.h
--- a/include/linux/lglock.h~lglock-map-to-spinlock-when-config_smp
+++ a/include/linux/lglock.h
@@ -35,6 +35,8 @@
#define DEFINE_BRLOCK(name) DEFINE_LGLOCK(name)
#define DEFINE_STATIC_BRLOCK(name) DEFINE_STATIC_LGLOCK(name)
+#ifdef CONFIG_SMP
+
#ifdef CONFIG_DEBUG_LOCK_ALLOC
#define LOCKDEP_INIT_MAP lockdep_init_map
#else
@@ -67,4 +69,18 @@ void lg_local_unlock_cpu(struct lglock *
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 -puN kernel/Makefile~lglock-map-to-spinlock-when-config_smp kernel/Makefile
--- a/kernel/Makefile~lglock-map-to-spinlock-when-config_smp
+++ a/kernel/Makefile
@@ -10,7 +10,7 @@ obj-y = fork.o exec_domain.o panic.o
kthread.o wait.o sys_ni.o posix-cpu-timers.o mutex.o \
hrtimer.o rwsem.o nsproxy.o srcu.o semaphore.o \
notifier.o ksysfs.o cred.o reboot.o \
- async.o range.o groups.o lglock.o smpboot.o
+ async.o range.o groups.o smpboot.o
ifdef CONFIG_FUNCTION_TRACER
# Do not trace debug files and internal ftrace files
@@ -50,7 +50,7 @@ obj-$(CONFIG_SMP) += smp.o
ifneq ($(CONFIG_SMP),y)
obj-y += up.o
endif
-obj-$(CONFIG_SMP) += spinlock.o
+obj-$(CONFIG_SMP) += lglock.o spinlock.o
obj-$(CONFIG_DEBUG_SPINLOCK) += spinlock.o
obj-$(CONFIG_PROVE_LOCKING) += spinlock.o
obj-$(CONFIG_UID16) += uid16.o
_
Patches currently in -mm which might be from josh@xxxxxxxxxxxxxxxx are
lglock-map-to-spinlock-when-config_smp.patch
checkpatch-report-missing-spaces-around-trigraphs-with-strict.patch
checkpatchpl-check-for-the-fsf-mailing-address.patch
documentation-abi-document-the-non-abi-status-of-kconfig-and-symbols.patch
scripts-bloat-o-meter-ignore-changes-in-the-size-of-linux_banner.patch
scripts-bloat-o-meter-use-startswith-rather-than-fragile-slicing.patch
linux-next.patch
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