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authorGerald Schaefer <gerald.schaefer@de.ibm.com>2010-11-22 15:47:36 +0100
committerIngo Molnar <mingo@elte.hu>2010-11-26 15:05:34 +0100
commit335d7afbfb71faac833734a94240c1e07cf0ead8 (patch)
tree483a24c6005af6eb25a256d92a697411d94a7458 /arch
parent22a867d81707b0a2720bb5f65255265b95d30526 (diff)
downloadlinux-335d7afbfb71faac833734a94240c1e07cf0ead8.tar.bz2
mutexes, sched: Introduce arch_mutex_cpu_relax()
The spinning mutex implementation uses cpu_relax() in busy loops as a compiler barrier. Depending on the architecture, cpu_relax() may do more than needed in this specific mutex spin loops. On System z we also give up the time slice of the virtual cpu in cpu_relax(), which prevents effective spinning on the mutex. This patch replaces cpu_relax() in the spinning mutex code with arch_mutex_cpu_relax(), which can be defined by each architecture that selects HAVE_ARCH_MUTEX_CPU_RELAX. The default is still cpu_relax(), so this patch should not affect other architectures than System z for now. Signed-off-by: Gerald Schaefer <gerald.schaefer@de.ibm.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> LKML-Reference: <1290437256.7455.4.camel@thinkpad> Signed-off-by: Ingo Molnar <mingo@elte.hu>
Diffstat (limited to 'arch')
-rw-r--r--arch/Kconfig3
-rw-r--r--arch/s390/Kconfig1
-rw-r--r--arch/s390/include/asm/mutex.h2
3 files changed, 6 insertions, 0 deletions
diff --git a/arch/Kconfig b/arch/Kconfig
index 8bf0fa652eb6..f78c2be4242b 100644
--- a/arch/Kconfig
+++ b/arch/Kconfig
@@ -175,4 +175,7 @@ config HAVE_PERF_EVENTS_NMI
config HAVE_ARCH_JUMP_LABEL
bool
+config HAVE_ARCH_MUTEX_CPU_RELAX
+ bool
+
source "kernel/gcov/Kconfig"
diff --git a/arch/s390/Kconfig b/arch/s390/Kconfig
index e0b98e71ff47..6c6d7b339aae 100644
--- a/arch/s390/Kconfig
+++ b/arch/s390/Kconfig
@@ -99,6 +99,7 @@ config S390
select HAVE_KERNEL_LZMA
select HAVE_KERNEL_LZO
select HAVE_GET_USER_PAGES_FAST
+ select HAVE_ARCH_MUTEX_CPU_RELAX
select ARCH_INLINE_SPIN_TRYLOCK
select ARCH_INLINE_SPIN_TRYLOCK_BH
select ARCH_INLINE_SPIN_LOCK
diff --git a/arch/s390/include/asm/mutex.h b/arch/s390/include/asm/mutex.h
index 458c1f7fbc18..688271f5f2e4 100644
--- a/arch/s390/include/asm/mutex.h
+++ b/arch/s390/include/asm/mutex.h
@@ -7,3 +7,5 @@
*/
#include <asm-generic/mutex-dec.h>
+
+#define arch_mutex_cpu_relax() barrier()