[PATCH] kexec: Avoid migration of already disabled irqs (ia64)

This patch fixes up ia64 kexec support for HP rx2620 hardware.  It does
this by skipping migration of already disabled irqs.  This is most likely a
problem on other ia64 platforms as well, but I've only been able to
reproduce it on one machine so far.

The full story is that handle_bad_irq() gets invoked before starting the
new kernel without this patch.  This seems to happen when fixup_irqs()
calls generic_handle_irq() on already migrated (and disabled) irqs.  So by
avoiding migration of disabled irqs we stay away of handle_bad_irq().

The code has been tested on three different ia64 machines, all with good
results.  It is possible to trigger the same bug by offlining a processor
using echo 0 > /sys/devices/system/cpu/cpuX/online.

More detailed information is available in the following mail thread:
http://lists.osdl.org/pipermail/fastboot/2007-January/thread.html#5774Signed-off-by: NMagnus Damm <magnus@valinux.co.jp>
Acked-by: NSimon Horman <horms@verge.net.au>
Acked-by: NZou, Nanhai <nanhai.zou@intel.com>
Acked-by: NJay Lan <jlan@sgi.com>
Acked-by: N"Luck, Tony" <tony.luck@intel.com>
Signed-off-by: NAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: NLinus Torvalds <torvalds@linux-foundation.org>

arch/ia64/kernel/irq.c

@@ -122,6 +122,9 @@ static void migrate_irqs(void)
 	for (irq=0; irq < NR_IRQS; irq++) {
 		desc = irq_desc + irq;
 
+		if (desc->status == IRQ_DISABLED)
+			continue;
+
 		/*
 		 * No handling for now.
 		 * TBD: Implement a disable function so we can now