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authorGerald Schaefer <gerald.schaefer@de.ibm.com>2010-11-22 17:47:36 +0300
committerIngo Molnar <mingo@elte.hu>2010-11-26 17:05:34 +0300
commit335d7afbfb71faac833734a94240c1e07cf0ead8 (patch)
tree483a24c6005af6eb25a256d92a697411d94a7458 /include/linux
parent22a867d81707b0a2720bb5f65255265b95d30526 (diff)
downloadlinux-335d7afbfb71faac833734a94240c1e07cf0ead8.tar.xz
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 'include/linux')
-rw-r--r--include/linux/mutex.h4
1 files changed, 4 insertions, 0 deletions
diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index f363bc8fdc74..94b48bd40dd7 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -160,4 +160,8 @@ extern int mutex_trylock(struct mutex *lock);
extern void mutex_unlock(struct mutex *lock);
extern int atomic_dec_and_mutex_lock(atomic_t *cnt, struct mutex *lock);
+#ifndef CONFIG_HAVE_ARCH_MUTEX_CPU_RELAX
+#define arch_mutex_cpu_relax() cpu_relax()
+#endif
+
#endif