Fix race in IO-APIC routing entry setup.

Interrupt could happen between setting the IO-APIC entry
and setting its interrupt data.

Pointed out by Linus.

Signed-off-by: Andi Kleen <ak@suse.de>

---
 arch/x86_64/kernel/io_apic.c |   12 +++++++++---
 1 files changed, 9 insertions(+), 3 deletions(-)

Index: linux/arch/x86_64/kernel/io_apic.c
===================================================================
--- linux.orig/arch/x86_64/kernel/io_apic.c
+++ linux/arch/x86_64/kernel/io_apic.c
@@ -175,14 +175,20 @@ static struct IO_APIC_route_entry ioapic
  * the interrupt, and we need to make sure the entry is fully populated
  * before that happens.
  */
-static void ioapic_write_entry(int apic, int pin, struct IO_APIC_route_entry e)
+static void
+__ioapic_write_entry(int apic, int pin, struct IO_APIC_route_entry e)
 {
-	unsigned long flags;
 	union entry_union eu;
 	eu.entry = e;
-	spin_lock_irqsave(&ioapic_lock, flags);
 	io_apic_write(apic, 0x11 + 2*pin, eu.w2);
 	io_apic_write(apic, 0x10 + 2*pin, eu.w1);
+}
+
+static void ioapic_write_entry(int apic, int pin, struct IO_APIC_route_entry e)
+{
+	unsigned long flags;
+	spin_lock_irqsave(&ioapic_lock, flags);
+	__ioapic_write_entry(apic, pin, e);
 	spin_unlock_irqrestore(&ioapic_lock, flags);
 }