[PATCH] i386: 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>

1 files changed, 11 insertions, 5 deletions

diff --git a/arch/i386/kernel/io_apic.c b/arch/i386/kernel/io_apic.c
index 3b7a63e0ed1a..e33b7a845299 100644
--- a/arch/i386/kernel/io_apic.c
+++ b/arch/i386/kernel/io_apic.c
@@ -153,14 +153,20 @@ static struct IO_APIC_route_entry ioapic_read_entry(int apic, int pin)
  * 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);
 }
 
@@ -1360,8 +1366,8 @@ static void __init setup_IO_APIC_irqs(void)
                         if (!apic && (irq < 16))
                                 disable_8259A_irq(irq);
                 }
-                ioapic_write_entry(apic, pin, entry);
                 spin_lock_irqsave(&ioapic_lock, flags);
+                __ioapic_write_entry(apic, pin, entry);
                 set_native_irq_info(irq, TARGET_CPUS);
                 spin_unlock_irqrestore(&ioapic_lock, flags);
         }
@@ -2856,8 +2862,8 @@ int io_apic_set_pci_routing (int ioapic, int pin, int irq, int edge_level, int a
         if (!ioapic && (irq < 16))
                 disable_8259A_irq(irq);
 
-        ioapic_write_entry(ioapic, pin, entry);
         spin_lock_irqsave(&ioapic_lock, flags);
+        __ioapic_write_entry(ioapic, pin, entry);
         set_native_irq_info(irq, TARGET_CPUS);
         spin_unlock_irqrestore(&ioapic_lock, flags);