The ia64_mca_cpe_int_handler() in 2.6.24 goes something like this:

ia64_mca_cpe_int_handler (int cpe_irq, void *arg)
{
...
	/* SAL spec states this should run w/ interrupts enabled */
	local_irq_enable();

	spin_lock(&cpe_history_lock);
...
	spin_unlock(&cpe_history_lock);

	ia64_mca_log_sal_error_record(SAL_INFO_TYPE_CPE);
}

I think the interrupts are enabled too early. I just have caught a dead lock:
I have got nested ia64_mca_cpe_int_handler()-s, the first instance has
been interrupted somewhere between spin_lock(&cpe_history_lock) and
spin_unlock(&cpe_history_lock). Obviously, the second instance will never get
the lock.
The previous versions, e.g. 2.6.18, were not safe either:

ia64_mca_cpe_int_handler (int cpe_irq, void *arg, struct pt_regs *ptregs)
{
...
        /* SAL spec states this should run w/ interrupts enabled */
        local_irq_enable();

        /* Get the CPE error record and log it */
        ia64_mca_log_sal_error_record(SAL_INFO_TYPE_CPE);

        spin_lock(&cpe_history_lock);
...
	spin_unlock(&cpe_history_lock);
}

I think the interrupts have to be blocked while we are inside the lock-
protected region.
I can think of something like this below. Please have a look at this patch.

Thanks,

Zoltan Menyhart