x86: apic - introduce dummy apic operations

Impact: refactor, speed up and robustize code

In case if apic was disabled by kernel option
or by hardware limits we can use dummy operations
in apic->write to simplify the ack_APIC_irq() code.

At the lame time the patch fixes the missed EOI in
do_IRQ function (which has place if kernel is compiled
as X86-32 and interrupt without handler happens where
apic was not asked to be disabled via kernel option).

Note that native_apic_write_dummy() consists of
WARN_ON_ONCE to catch any buggy writes on enabled
APICs. Could be removed after some time of testing.

Signed-off-by: Cyrill Gorcunov <gorcunov@openvz.org>
LKML-Reference: <20090412165058.724788431@openvz.org>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

1 files changed, 2 insertions, 8 deletions

diff --git a/arch/x86/kernel/irq.c b/arch/x86/kernel/irq.c
index 6603492e8b71..fd57bf35d0fc 100644
--- a/arch/x86/kernel/irq.c
+++ b/arch/x86/kernel/irq.c
@@ -27,7 +27,6 @@ void ack_bad_irq(unsigned int irq)
         if (printk_ratelimit())
                 pr_err("unexpected IRQ trap at vector %02x\n", irq);
 
-#ifdef CONFIG_X86_LOCAL_APIC
         /*
          * Currently unexpected vectors happen only on SMP and APIC.
          * We _must_ ack these because every local APIC has only N
@@ -37,9 +36,7 @@ void ack_bad_irq(unsigned int irq)
          * completely.
          * But only ack when the APIC is enabled -AK
          */
-        if (cpu_has_apic)
-                ack_APIC_irq();
-#endif
+        ack_APIC_irq();
 }
 
 #define irq_stats(x)            (&per_cpu(irq_stat, x))
@@ -214,10 +211,7 @@ unsigned int __irq_entry do_IRQ(struct pt_regs *regs)
         irq = __get_cpu_var(vector_irq)[vector];
 
         if (!handle_irq(irq, regs)) {
-#ifdef CONFIG_X86_64
-                if (!disable_apic)
-                        ack_APIC_irq();
-#endif
+                ack_APIC_irq();
 
                 if (printk_ratelimit())
                         pr_emerg("%s: %d.%d No irq handler for vector (irq %d)\n",