x86/apic: Disable I/O APIC before shutdown of the local APIC

In reboot and crash path, when we shut down the local APIC, the I/O APIC is
still active. This may cause issues because external interrupts
can still come in and disturb the local APIC during shutdown process.

To quiet external interrupts, disable I/O APIC before shutdown local APIC.
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
Link: http://lkml.kernel.org/r/1382578212-4677-1-git-send-email-fenghua.yu@intel.com
Cc: <stable@kernel.org>
[ I suppose the 'issue' is a hang during shutdown. It's a fine change nevertheless. ]
Signed-off-by: Ingo Molnar <mingo@kernel.org>

arch/x86/kernel/crash.c

@@ -127,12 +127,12 @@ void native_machine_crash_shutdown(struct pt_regs *regs)
 	cpu_emergency_vmxoff();
 	cpu_emergency_svm_disable();
 
-	lapic_shutdown();
 #ifdef CONFIG_X86_IO_APIC
 	/* Prevent crash_kexec() from deadlocking on ioapic_lock. */
 	ioapic_zap_locks();
 	disable_IO_APIC();
 #endif
+	lapic_shutdown();
 #ifdef CONFIG_HPET_TIMER
 	hpet_disable();
 #endif

arch/x86/kernel/reboot.c

@@ -550,6 +550,10 @@ static void native_machine_emergency_restart(void)
 void native_machine_shutdown(void)
 {
 	/* Stop the cpus and apics */
+#ifdef CONFIG_X86_IO_APIC
+	disable_IO_APIC();
+#endif
+
 #ifdef CONFIG_SMP
 	/*
 	 * Stop all of the others. Also disable the local irq to
@@ -562,10 +566,6 @@ void native_machine_shutdown(void)
 
 	lapic_shutdown();
 
-#ifdef CONFIG_X86_IO_APIC
-	disable_IO_APIC();
-#endif
-
 #ifdef CONFIG_HPET_TIMER
 	hpet_disable();
 #endif