* Anton Blanchard [off-list ref] wrote:

+static arch_spinlock_t die_lock = __ARCH_SPIN_LOCK_UNLOCKED;
+static int die_owner = -1;
+static unsigned int die_nest_count;
+
+unsigned long __die_spin_lock_irqsave(void)
+{
+	unsigned long flags;
+	int cpu;
+
+	/* racy, but better than risking deadlock. */
+	raw_local_irq_save(flags);
+
+	cpu = smp_processor_id();
+	if (!arch_spin_trylock(&die_lock)) {
+		if (cpu != die_owner)
+			arch_spin_lock(&die_lock);

So why not trylock and time out here after a few seconds, 
instead of indefinitely supressing some potentially vital 
output due to some other CPU crashing/locking with the lock 
held?

+	}
+	die_nest_count++;
+	die_owner = cpu;
+
+	return flags;

I suspect this would work in most cases.

If we fix the deadlock potential, and get a true global 
ordering of various oopses/warnings as they triggered (or 
at least timestamping them), then I'm sold on this I guess, 
it will likely improve things.

Thanks,

	Ingo