x86: Don't unmask disabled irqs when migrating them

It doesn't make sense to unconditionally unmask a disabled irq when
migrating it from offlined cpu to another. If the irq triggers then it
will be disabled in the interrupt handler anyway. So we can just avoid
unmasking it.

[ tglx: Made masking unconditional again and fixed the changelog ]
Signed-off-by: NFengzhe Zhang <fengzhe.zhang@intel.com>
Signed-off-by: NKevin Tian <kevin.tian@intel.com>
Cc: Ian Campbell <Ian.Campbell@citrix.com>
Cc: Jan Beulich <JBeulich@novell.com>
Cc: "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
Link: http://lkml.kernel.org/r/%3C625BA99ED14B2D499DC4E29D8138F1505C8ED7F7E3%40shsmsx502.ccr.corp.intel.com%3ESigned-off-by: NThomas Gleixner <tglx@linutronix.de>

arch/x86/kernel/irq.c

@@ -276,7 +276,8 @@ void fixup_irqs(void)
 		else if (!(warned++))
 			set_affinity = 0;
 
-		if (!irqd_can_move_in_process_context(data) && chip->irq_unmask)
+		if (!irqd_can_move_in_process_context(data) &&
+		    !irqd_irq_disabled(data) && chip->irq_unmask)
 			chip->irq_unmask(data);
 
 		raw_spin_unlock(&desc->lock);