[PATCH] x86_64: make touch_nmi_watchdog() not touch impossible cpus' private data

Along with that, also suppress the memory touching altogether when the
watchdog is not running, to eliminate needless crosstalk. Plus ad a call
to it to make things consistent (one could also consider removing the call
in enable_timer_nmi_watchdog()).

Signed-off-by: Jan Beulich <jbeulich@novell.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 11 insertions, 8 deletions

diff --git a/arch/x86_64/kernel/nmi.c b/arch/x86_64/kernel/nmi.c
index 8be407a1f62d..5bf17e41cd2d 100644
--- a/arch/x86_64/kernel/nmi.c
+++ b/arch/x86_64/kernel/nmi.c
@@ -236,6 +236,7 @@ static void enable_lapic_nmi_watchdog(void)
 {
         if (nmi_active < 0) {
                 nmi_watchdog = NMI_LOCAL_APIC;
+                touch_nmi_watchdog();
                 setup_apic_nmi_watchdog();
         }
 }
@@ -456,15 +457,17 @@ static DEFINE_PER_CPU(int, nmi_touch);
 
 void touch_nmi_watchdog (void)
 {
-        int i;
+        if (nmi_watchdog > 0) {
+                unsigned cpu;
 
-        /*
-         * Tell other CPUs to reset their alert counters. We cannot
-         * do it ourselves because the alert count increase is not
-         * atomic.
-         */
-        for (i = 0; i < NR_CPUS; i++)
-                per_cpu(nmi_touch, i) = 1;
+                /*
+                 * Tell other CPUs to reset their alert counters. We cannot
+                 * do it ourselves because the alert count increase is not
+                 * atomic.
+                 */
+                for_each_present_cpu (cpu)
+                        per_cpu(nmi_touch, cpu) = 1;
+        }
 
         touch_softlockup_watchdog();
 }