x86_64: speedup touch_nmi_watchdog
Avoid dirtying remote cpu's memory if it already has the correct value.
Cc: Andi Kleen <ak@suse.de>
Cc: Konrad Rzeszutek <konrad@darnok.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
diff --git a/arch/x86_64/kernel/nmi.c b/arch/x86_64/kernel/nmi.c
index 931c64b..edbbc59 100644
--- a/arch/x86_64/kernel/nmi.c
+++ b/arch/x86_64/kernel/nmi.c
@@ -296,7 +296,7 @@
static DEFINE_PER_CPU(local_t, alert_counter);
static DEFINE_PER_CPU(int, nmi_touch);
-void touch_nmi_watchdog (void)
+void touch_nmi_watchdog(void)
{
if (nmi_watchdog > 0) {
unsigned cpu;
@@ -306,8 +306,10 @@
* do it ourselves because the alert count increase is not
* atomic.
*/
- for_each_present_cpu (cpu)
- per_cpu(nmi_touch, cpu) = 1;
+ for_each_present_cpu(cpu) {
+ if (per_cpu(nmi_touch, cpu) != 1)
+ per_cpu(nmi_touch, cpu) = 1;
+ }
}
touch_softlockup_watchdog();