Commit 267eb01a authored by Andreas Mohr's avatar Andreas Mohr Committed by Linus Torvalds

i386: add cpu_relax() to cmos_lock()

Add cpu_relax() to cmos_lock() inline function for faster operation on SMT
CPUs and less power consumption on others in case of lock contention (which
probably doesn't happen too often, so admittedly this patch is not too
exciting).

[akpm@linux-foundation.org: Include the header file for cpu_relax()]
Signed-off-by: default avatarAndreas Mohr <andi@lisas.de>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarAndi Kleen <ak@suse.de>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 8f03d6ce
...@@ -6,6 +6,7 @@ ...@@ -6,6 +6,7 @@
#include <asm/io.h> #include <asm/io.h>
#include <asm/system.h> #include <asm/system.h>
#include <asm/processor.h>
#include <linux/mc146818rtc.h> #include <linux/mc146818rtc.h>
#ifndef RTC_PORT #ifndef RTC_PORT
...@@ -43,8 +44,10 @@ static inline void lock_cmos(unsigned char reg) ...@@ -43,8 +44,10 @@ static inline void lock_cmos(unsigned char reg)
unsigned long new; unsigned long new;
new = ((smp_processor_id()+1) << 8) | reg; new = ((smp_processor_id()+1) << 8) | reg;
for (;;) { for (;;) {
if (cmos_lock) if (cmos_lock) {
cpu_relax();
continue; continue;
}
if (__cmpxchg(&cmos_lock, 0, new, sizeof(cmos_lock)) == 0) if (__cmpxchg(&cmos_lock, 0, new, sizeof(cmos_lock)) == 0)
return; return;
} }
......
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