From: Aristeu Rozanski <aris@redhat.com>
Date: Wed, 20 Aug 2008 13:16:54 -0400
Subject: [x86_64] nmi: update reserve_lapic_nmi
Message-id: 20080820171648.428392000@redhat.com
O-Subject: [RHEL5.3 PATCH 08/25] nmi: update reserve_lapic_nmi
Bugzilla: 447618

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

Fix {reserve,release}_lapic_nmi() so it'll behave the same

upstream: not upstream, makes sense only for RHEL-5

diff --git a/arch/x86_64/kernel/nmi.c b/arch/x86_64/kernel/nmi.c
index c25934c..e5766aa 100644
--- a/arch/x86_64/kernel/nmi.c
+++ b/arch/x86_64/kernel/nmi.c
@@ -30,19 +30,7 @@
 
 int unknown_nmi_panic;
 int panic_on_unrecovered_nmi;
-/*
- * lapic_nmi_owner tracks the ownership of the lapic NMI hardware:
- * - it may be reserved by some other driver, or not
- * - when not reserved by some other driver, it may be used for
- *   the NMI watchdog, or not
- *
- * This is maintained separately from nmi_active because the NMI
- * watchdog may also be driven from the I/O APIC timer.
- */
-static DEFINE_SPINLOCK(lapic_nmi_owner_lock);
-static unsigned int lapic_nmi_owner;
-#define LAPIC_NMI_WATCHDOG	(1<<0)
-#define LAPIC_NMI_RESERVED	(1<<1)
+static atomic_t lapic_nmi_reserved = ATOMIC_INIT(0);
 
 /* nmi_active:
  * +1: the lapic NMI watchdog is active, but can be disabled
@@ -201,7 +189,6 @@ int __init check_nmi_watchdog (void)
 			       cpu_pda(cpu)->__nmi_count);
 			if (atomic_dec_and_test(&nmi_watchdog_active))
 				nmi_active = 0;
-			lapic_nmi_owner &= ~LAPIC_NMI_WATCHDOG;
 			nmi_perfctr_msr = 0;
 			kfree(counts);
 			return -1;
@@ -252,31 +239,25 @@ int __init setup_nmi_watchdog(char *str)
 
 __setup("nmi_watchdog=", setup_nmi_watchdog);
 
+void acpi_nmi_enable(void);
+void acpi_nmi_disable(void);
 int reserve_lapic_nmi(void)
 {
-	unsigned int old_owner;
-
-	spin_lock(&lapic_nmi_owner_lock);
-	old_owner = lapic_nmi_owner;
-	lapic_nmi_owner |= LAPIC_NMI_RESERVED;
-	spin_unlock(&lapic_nmi_owner_lock);
-	if (old_owner & LAPIC_NMI_RESERVED)
-		return -EBUSY;
-	if (old_owner & LAPIC_NMI_WATCHDOG)
-		disable_lapic_nmi_watchdog();
-	return 0;
+	if (!test_and_set_bit(1, &lapic_nmi_reserved)) {
+		if (nmi_watchdog == NMI_LOCAL_APIC)
+			disable_lapic_nmi_watchdog();
+		return 0;
+	}
+	return 1;
 }
 
 void release_lapic_nmi(void)
 {
-	unsigned int new_owner;
-
-	spin_lock(&lapic_nmi_owner_lock);
-	new_owner = lapic_nmi_owner & ~LAPIC_NMI_RESERVED;
-	lapic_nmi_owner = new_owner;
-	spin_unlock(&lapic_nmi_owner_lock);
-	if (new_owner & LAPIC_NMI_WATCHDOG)
+	if (nmi_watchdog == NMI_LOCAL_APIC) {
 		enable_lapic_nmi_watchdog();
+		touch_nmi_watchdog();
+	}
+	clear_bit(1, &lapic_nmi_reserved);
 }
 
 static int old_ioapic_count;