[PATCH] Make i386 die() more resilient against recursive errors

Make i386 die() more resilient against recursive errors, almost a cut
and paste of the ia64 die() routine.  Much of the patch is indentation
changes.

Mainly to make it easier to add crash, lcrash, kmsgdump or other RAS patches. 
They are invoked from die() and if they crash themselves, we have to avoid
recursive loops in die().
Signed-off-by: Keith Owens <kaos@sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

arch/i386/kernel/traps.c

@@ -292,35 +292,52 @@ static void handle_BUG(struct pt_regs *regs)
 	printk("Kernel BUG\n");
 }
 
-spinlock_t die_lock = SPIN_LOCK_UNLOCKED;
-
 void die(const char * str, struct pt_regs * regs, long err)
 {
+	static struct {
+		spinlock_t lock;
+		u32 lock_owner;
+		int lock_owner_depth;
+	} die = {
+		.lock =			SPIN_LOCK_UNLOCKED,
+		.lock_owner =		-1,
+		.lock_owner_depth =	0
+	};
 	static int die_counter;
-	int nl = 0;
 
-	console_verbose();
-	spin_lock_irq(&die_lock);
-	bust_spinlocks(1);
-	handle_BUG(regs);
-	printk(KERN_ALERT "%s: %04lx [#%d]\n", str, err & 0xffff, ++die_counter);
+	if (die.lock_owner != smp_processor_id()) {
+		console_verbose();
+		spin_lock_irq(&die.lock);
+		die.lock_owner = smp_processor_id();
+		die.lock_owner_depth = 0;
+		bust_spinlocks(1);
+	}
+
+	if (++die.lock_owner_depth < 3) {
+		int nl = 0;
+		handle_BUG(regs);
+		printk(KERN_ALERT "%s: %04lx [#%d]\n", str, err & 0xffff, ++die_counter);
 #ifdef CONFIG_PREEMPT
-	printk("PREEMPT ");
-	nl = 1;
+		printk("PREEMPT ");
+		nl = 1;
 #endif
 #ifdef CONFIG_SMP
-	printk("SMP ");
-	nl = 1;
+		printk("SMP ");
+		nl = 1;
 #endif
 #ifdef CONFIG_DEBUG_PAGEALLOC
-	printk("DEBUG_PAGEALLOC");
-	nl = 1;
+		printk("DEBUG_PAGEALLOC");
+		nl = 1;
 #endif
-	if (nl)
-		printk("\n");
-	show_registers(regs);
+		if (nl)
+			printk("\n");
+		show_registers(regs);
+  	} else
+		printk(KERN_ERR "Recursive die() failure, output suppressed\n");
+
 	bust_spinlocks(0);
-	spin_unlock_irq(&die_lock);
+	die.lock_owner = -1;
+	spin_unlock_irq(&die.lock);
 	if (in_interrupt())
 		panic("Fatal exception in interrupt");