NUMA-Q breakage 3/7 irqbalance stuffs unreachable cpu's in IO-APICS

irqbalance stuffs unreachable cpus' APIC ID's into the IO-APICs. This cannot be done generically, as the cpu's that can be reached from a given IO-APIC depend on the subarch. The net effect of the bug is deadlocking while waiting for interrupts to come back from devices, i.e. booting is impossible.

Fix (due to Matt Dobson) below.

Cheers,
Bill

diff -Nur linux-2.5.23-vanilla/arch/i386/kernel/io_apic.c linux-2.5.23-patched/arch/i386/kernel/io_apic.c
@@ -247,7 +247,7 @@
 
 static inline void balance_irq(int irq)
 {
-#if CONFIG_SMP
+#if (CONFIG_SMP && !CONFIG_MULTIQUAD)
 	irq_balance_t *entry = irq_balance + irq;
 	unsigned long now = jiffies;