[PATCH] do_nmi needs irq_enter/irq_exit lovin...

Use new "nmi_enter/exit()" which acts the same as the regular irq
entries (increases the preempt count appropriately), but doesn't try to
start processing softirqs on nmi exit (it just decreases the count).

arch/i386/kernel/traps.c

@@ -526,12 +526,17 @@ static nmi_callback_t nmi_callback = dummy_nmi_callback;
  
 asmlinkage void do_nmi(struct pt_regs * regs, long error_code)
 {
-	int cpu = smp_processor_id();
+	int cpu;
 
+	nmi_enter();
+
+	cpu = smp_processor_id();
 	++nmi_count(cpu);
 
 	if (!nmi_callback(regs, cpu))
 		default_do_nmi(regs);
+
+	nmi_exit();
 }
 
 void set_nmi_callback(nmi_callback_t callback)

include/asm-i386/hardirq.h

@@ -76,6 +76,8 @@ typedef struct {
 #define hardirq_endlock()	do { } while (0)
 
 #define irq_enter()		(preempt_count() += HARDIRQ_OFFSET)
+#define nmi_enter()		(irq_enter())
+#define nmi_exit()		(preempt_count() -= HARDIRQ_OFFSET)
 
 #if CONFIG_PREEMPT
 # define in_atomic()	((preempt_count() & ~PREEMPT_ACTIVE) != kernel_locked())