Revert "Revert "x86: fix ioapic bug again""

This reverts commit 0b6a39f7.

The changes in tip/x86/apic solve this better.
Signed-off-by: Ingo Molnar <mingo@elte.hu>

arch/x86/kernel/io_apic_32.c

@@ -2130,10 +2130,14 @@ static inline void __init check_timer(void)
 {
 	int apic1, pin1, apic2, pin2;
 	int vector;
+	unsigned int ver;
 	unsigned long flags;
 
 	local_irq_save(flags);
 
+	ver = apic_read(APIC_LVR);
+	ver = GET_APIC_VERSION(ver);
+
 	/*
 	 * get/set the timer IRQ vector:
 	 */
@@ -2146,11 +2150,15 @@ static inline void __init check_timer(void)
 	 * mode for the 8259A whenever interrupts are routed
 	 * through I/O APICs.  Also IRQ0 has to be enabled in
 	 * the 8259A which implies the virtual wire has to be
-	 * disabled in the local APIC.
+	 * disabled in the local APIC.  Finally timer interrupts
+	 * need to be acknowledged manually in the 8259A for
+	 * timer_interrupt() and for the i82489DX when using
+	 * the NMI watchdog.
 	 */
 	apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);
 	init_8259A(1);
-	timer_ack = 1;
+	timer_ack = !cpu_has_tsc;
+	timer_ack |= (nmi_watchdog == NMI_IO_APIC && !APIC_INTEGRATED(ver));
 	if (timer_over_8254 > 0)
 		enable_8259A_irq(0);
 

arch/x86/kernel/nmi_32.c

@@ -26,6 +26,7 @@
 
 #include <asm/smp.h>
 #include <asm/nmi.h>
+#include <asm/timer.h>
 
 #include "mach_traps.h"
 
@@ -81,7 +82,7 @@ int __init check_nmi_watchdog(void)
 
 	prev_nmi_count = kmalloc(NR_CPUS * sizeof(int), GFP_KERNEL);
 	if (!prev_nmi_count)
-		return -1;
+		goto error;
 
 	printk(KERN_INFO "Testing NMI watchdog ... ");
 
@@ -118,7 +119,7 @@ int __init check_nmi_watchdog(void)
 	if (!atomic_read(&nmi_active)) {
 		kfree(prev_nmi_count);
 		atomic_set(&nmi_active, -1);
-		return -1;
+		goto error;
 	}
 	printk("OK.\n");
 
@@ -129,6 +130,10 @@ int __init check_nmi_watchdog(void)
 
 	kfree(prev_nmi_count);
 	return 0;
+error:
+	timer_ack = !cpu_has_tsc;
+
+	return -1;
 }
 
 static int __init setup_nmi_watchdog(char *str)