[Xen-changelog] [xen-4.1-testing] x86: fix boot-time watchdog test.

[Xen patchbot-4.1-testing <patchbot@xxxxxxx>]

# HG changeset patch
# User Tim Deegan <Tim.Deegan@xxxxxxxxxx>
# Date 1309249920 -3600
# Node ID 45f5bdc1a90a2b1eb7b42e13be3dd28febcd14eb
# Parent  eab9c077003c7df47811ce6fb8d0539708383d95
x86: fix boot-time watchdog test.

Since the perf counter that the LAPIC NMI watchdog uses only
runs while the core isn't halted, and all APs are idle at
this point in the boot process, it's possible that remote
CPUs won't see any NMIs during the 10-tick waiting period.
Force all CPUs to busy-wait so we know the timers are running.

Signed-off-by: Tim Deegan <Tim.Deegan@xxxxxxxxxx>
xen-unstable changeset:   23612:6c7a23e08a04
xen-unstable date:        Tue Jun 28 09:16:13 2011 +0100
---


diff -r eab9c077003c -r 45f5bdc1a90a xen/arch/x86/nmi.c
--- a/xen/arch/x86/nmi.c        Thu Jun 23 12:03:13 2011 +0100
+++ b/xen/arch/x86/nmi.c        Tue Jun 28 09:32:00 2011 +0100
@@ -95,6 +95,11 @@
     (P4_CCCR_OVF_PMI0|P4_CCCR_THRESHOLD(15)|P4_CCCR_COMPLEMENT| \
      P4_CCCR_COMPARE|P4_CCCR_REQUIRED|P4_CCCR_ESCR_SELECT(4)|P4_CCCR_ENABLE)
 
+static void __init wait_for_nmis(void *p)
+{
+    mdelay((10*1000)/nmi_hz); /* wait 10 ticks */
+}
+
 int __init check_nmi_watchdog (void)
 {
     static unsigned int __initdata prev_nmi_count[NR_CPUS];
@@ -108,7 +113,12 @@
     for_each_online_cpu ( cpu )
         prev_nmi_count[cpu] = nmi_count(cpu);
     local_irq_enable();
-    mdelay((10*1000)/nmi_hz); /* wait 10 ticks */
+
+    /* Wait for 10 ticks.  Busy-wait on all CPUs: the LAPIC counter that
+     * the NMI watchdog uses only runs while the core's not halted */
+    if ( nmi_watchdog == NMI_LOCAL_APIC )
+        smp_call_function(wait_for_nmis, NULL, 0);
+    wait_for_nmis(NULL);
 
     for_each_online_cpu ( cpu )
     {

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