x86, nmi: Track NMI usage stats

Now that the NMI handler are broken into lists, increment the appropriate
stats for each list.  This allows us to see what is going on when they
get printed out in the next patch.

Signed-off-by: Don Zickus <dzickus@redhat.com>
Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Link: http://lkml.kernel.org/r/1317409584-23662-6-git-send-email-dzickus@redhat.com
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/nmi.c

@@ -53,6 +53,15 @@ static struct nmi_desc nmi_desc[NMI_MAX] =
 
 };
 
+struct nmi_stats {
+	unsigned int normal;
+	unsigned int unknown;
+	unsigned int external;
+	unsigned int swallow;
+};
+
+static DEFINE_PER_CPU(struct nmi_stats, nmi_stats);
+
 static int ignore_nmis;
 
 int unknown_nmi_panic;
@@ -262,8 +271,13 @@ unknown_nmi_error(unsigned char reason, struct pt_regs *regs)
 	 * if it caused the NMI)
 	 */
 	handled = nmi_handle(NMI_UNKNOWN, regs, false);
-	if (handled)
+	if (handled) {
+		__this_cpu_add(nmi_stats.unknown, handled);
 		return;
+	}
+
+	__this_cpu_add(nmi_stats.unknown, 1);
+
 #ifdef CONFIG_MCA
 	/*
 	 * Might actually be able to figure out what the guilty party
@@ -314,6 +328,7 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
 	__this_cpu_write(last_nmi_rip, regs->ip);
 
 	handled = nmi_handle(NMI_LOCAL, regs, b2b);
+	__this_cpu_add(nmi_stats.normal, handled);
 	if (handled) {
 		/*
 		 * There are cases when a NMI handler handles multiple
@@ -344,6 +359,7 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
 		 */
 		reassert_nmi();
 #endif
+		__this_cpu_add(nmi_stats.external, 1);
 		raw_spin_unlock(&nmi_reason_lock);
 		return;
 	}
@@ -380,7 +396,7 @@ static notrace __kprobes void default_do_nmi(struct pt_regs *regs)
 	 * for now.
 	 */
 	if (b2b && __this_cpu_read(swallow_nmi))
-		;
+		__this_cpu_add(nmi_stats.swallow, 1);
 	else
 		unknown_nmi_error(reason, regs);
 }