From: Andreas Mohr <[email protected]>
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).
[[email protected]: Include the header file for cpu_relax()]
Signed-off-by: Andreas Mohr <[email protected]>
Signed-off-by: Andi Kleen <[email protected]>
Cc: Andi Kleen <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
---
include/asm-i386/mc146818rtc.h | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
Index: linux/include/asm-i386/mc146818rtc.h
===================================================================
--- linux.orig/include/asm-i386/mc146818rtc.h
+++ linux/include/asm-i386/mc146818rtc.h
@@ -6,6 +6,7 @@
#include <asm/io.h>
#include <asm/system.h>
+#include <asm/processor.h>
#include <linux/mc146818rtc.h>
#ifndef RTC_PORT
@@ -43,8 +44,10 @@ static inline void lock_cmos(unsigned ch
unsigned long new;
new = ((smp_processor_id()+1) << 8) | reg;
for (;;) {
- if (cmos_lock)
+ if (cmos_lock) {
+ cpu_relax();
continue;
+ }
if (__cmpxchg(&cmos_lock, 0, new, sizeof(cmos_lock)) == 0)
return;
}
-
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