From: Aristeu Rozanski <aris@redhat.com>
Date: Wed, 20 Aug 2008 13:17:10 -0400
Subject: [x86] nmi: fix disable and enable _timer_nmi_watchdog
Message-id: 20080820171652.199458000@redhat.com
O-Subject: [RHEL5.3 PATCH 24/25] nmi: fix disable and enable _timer_nmi_watchdog()
Bugzilla: 447618

https://bugzilla.redhat.com/show_bug.cgi?id=447618

{disable_enable}_timer_nmi_watchdog() is used to provide oprofile a periodic
timer. These functions disable/enable the NMI watchdog (but not the periodic
NMIs) in the case IO_APIC is being used.

fix {disable,enable}_timer_nmi_watchdog() so nmi_watchdog variable won't be
changed.

upstream: not relevant upstream, both functions aren't used since
          2fbe7b25c8edaf2d10e6c1a4cc9f8afe714c4764

diff --git a/arch/i386/kernel/nmi.c b/arch/i386/kernel/nmi.c
index 956ffb5..8a17646 100644
--- a/arch/i386/kernel/nmi.c
+++ b/arch/i386/kernel/nmi.c
@@ -179,21 +179,16 @@ void release_lapic_nmi(void)
 static int old_ioapic_count;
 void disable_timer_nmi_watchdog(void)
 {
-	if ((nmi_watchdog != NMI_IO_APIC) ||
-	    (atomic_read(&nmi_watchdog_active) <= 0))
-		return;
-
 	unset_nmi_callback();
 	old_ioapic_count = atomic_read(&nmi_watchdog_active);
 	atomic_set(&nmi_watchdog_active, -1);
 	nmi_active = -1;
-	nmi_watchdog = NMI_NONE;
 }
 
 void enable_timer_nmi_watchdog(void)
 {
-	if (atomic_read(&nmi_watchdog_active) < 0) {
-		nmi_watchdog = NMI_IO_APIC;
+	if (nmi_watchdog == NMI_IO_APIC &&
+	    atomic_read(&nmi_watchdog_active) < 0) {
 		atomic_set(&nmi_watchdog_active, old_ioapic_count);
 		touch_nmi_watchdog();
 		nmi_active = 1;
@@ -366,7 +361,6 @@ extern void die_nmi(struct pt_regs *, const char *msg);
 
 int nmi_watchdog_tick (struct pt_regs * regs)
 {
-
 	/*
 	 * Since current_thread_info()-> is always on the stack, and we
 	 * always switch the stack NMI-atomically, it's safe to use