From: Andrew Morton <akpm@linux-foundation.org>
Date: Tue, 17 Jul 2007 11:03:58 +0000 (-0700)
Subject: x86_64: speedup touch_nmi_watchdog
X-Git-Tag: v2.6.23-rc1~705
X-Git-Url: http://pilppa.org/gitweb/gitweb.cgi?a=commitdiff_plain;h=567f3e422a9a155d7c7643148efb5bf959065d34;p=linux-2.6-omap-h63xx.git

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 931c64bad5e..edbbc59b752 100644
--- a/arch/x86_64/kernel/nmi.c
+++ b/arch/x86_64/kernel/nmi.c
@@ -296,7 +296,7 @@ static DEFINE_PER_CPU(unsigned, last_irq_sum);
 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 @@ void touch_nmi_watchdog (void)
 		 * 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();