From 0551130cc2e3b1fb559cf20c590370e7b4282864 Mon Sep 17 00:00:00 2001
From: Don Zickus <dzickus@redhat.com>
Date: Thu, 6 Jan 2011 16:18:51 -0500
Subject: [PATCH] --- yaml --- r: 228938 b: refs/heads/master c:
 ab846f13f69fa64f8ed69ce0c3e239e075910d23 h: refs/heads/master v: v3

---
 [refs]                        |  2 +-
 trunk/arch/x86/kernel/traps.c | 16 ++++++++++------
 2 files changed, 11 insertions(+), 7 deletions(-)

diff --git a/[refs] b/[refs]
index 09405083fa17..f1843c552dac 100644
--- a/[refs]
+++ b/[refs]
@@ -1,2 +1,2 @@
 ---
-refs/heads/master: c410b8307702c1e1f35be3fd868ad18e4ba0410f
+refs/heads/master: ab846f13f69fa64f8ed69ce0c3e239e075910d23
diff --git a/trunk/arch/x86/kernel/traps.c b/trunk/arch/x86/kernel/traps.c
index 23f6ac05d04c..613b3d284a89 100644
--- a/trunk/arch/x86/kernel/traps.c
+++ b/trunk/arch/x86/kernel/traps.c
@@ -84,6 +84,11 @@ EXPORT_SYMBOL_GPL(used_vectors);
 static int ignore_nmis;
 
 int unknown_nmi_panic;
+/*
+ * Prevent NMI reason port (0x61) being accessed simultaneously, can
+ * only be used in NMI handler.
+ */
+static DEFINE_RAW_SPINLOCK(nmi_reason_lock);
 
 static inline void conditional_sti(struct pt_regs *regs)
 {
@@ -392,7 +397,6 @@ unknown_nmi_error(unsigned char reason, struct pt_regs *regs)
 static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
 {
 	unsigned char reason = 0;
-	int cpu;
 
 	/*
 	 * CPU-specific NMI must be processed before non-CPU-specific
@@ -402,13 +406,12 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
 	if (notify_die(DIE_NMI, "nmi", regs, 0, 2, SIGINT) == NOTIFY_STOP)
 		return;
 
-	cpu = smp_processor_id();
-
-	/* Only the BSP gets external NMIs from the system. */
-	if (!cpu)
-		reason = get_nmi_reason();
+	/* Non-CPU-specific NMI: NMI sources can be processed on any CPU */
+	raw_spin_lock(&nmi_reason_lock);
+	reason = get_nmi_reason();
 
 	if (!(reason & NMI_REASON_MASK)) {
+		raw_spin_unlock(&nmi_reason_lock);
 		unknown_nmi_error(reason, regs);
 
 		return;
@@ -426,6 +429,7 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
 	 */
 	reassert_nmi();
 #endif
+	raw_spin_unlock(&nmi_reason_lock);
 }
 
 dotraplinkage notrace __kprobes void