1 files changed, 9 insertions, 11 deletions

diff --git a/arch/x86/kernel/io_apic_32.c b/arch/x86/kernel/io_apic_32.c
index a40d54fc1fdd..c64b3f5cc121 100644
--- a/arch/x86/kernel/io_apic_32.c
+++ b/arch/x86/kernel/io_apic_32.c
@@ -2146,19 +2146,17 @@ static inline void __init check_timer(void)
         set_intr_gate(vector, interrupt[0]);
 
         /*
-         * Subtle, code in do_timer_interrupt() expects an AEOI
-         * 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.  Finally timer interrupts
-         * need to be acknowledged manually in the 8259A for
-         * timer_interrupt() and for the i82489DX when using
-         * the NMI watchdog.
+         * As IRQ0 is to be enabled in the 8259A, the virtual
+         * wire has to be disabled in the local APIC.  Also
+         * timer interrupts need to be acknowledged manually in
+         * the 8259A for the i82489DX when using the NMI
+         * watchdog as that APIC treats NMIs as level-triggered.
+         * The AEOI mode will finish them in the 8259A
+         * automatically.
          */
         apic_write_around(APIC_LVT0, APIC_LVT_MASKED | APIC_DM_EXTINT);
         init_8259A(1);
-        timer_ack = !cpu_has_tsc;
-        timer_ack |= (nmi_watchdog == NMI_IO_APIC && !APIC_INTEGRATED(ver));
+        timer_ack = (nmi_watchdog == NMI_IO_APIC && !APIC_INTEGRATED(ver));
         if (timer_over_8254 > 0)
                 enable_8259A_irq(0);
 
@@ -2219,6 +2217,7 @@ static inline void __init check_timer(void)
                 printk(KERN_WARNING "timer doesn't work through the IO-APIC - disabling NMI Watchdog!\n");
                 nmi_watchdog = 0;
         }
+        timer_ack = 0;
 
         printk(KERN_INFO "...trying to set up timer as Virtual Wire IRQ...");
 
@@ -2237,7 +2236,6 @@ static inline void __init check_timer(void)
 
         printk(KERN_INFO "...trying to set up timer as ExtINT IRQ...");
 
-        timer_ack = 0;
         init_8259A(0);
         make_8259A_irq(0);
         apic_write_around(APIC_LVT0, APIC_DM_EXTINT);