Currently set_rte() changes RTE without iosapic_lock held. I guess it
assumes to be called only at the boot time. But set_rte() can be
called by PCI driver not only at the boot time. So I think set_rte()
should get iosapic_lock.

pci_enable_device(drivers/pci/pci.c)
|
+-> pci_enable_device_bars(drivers/pci/pci.c)
    |
    +-> pcibios_enable_device(arch/ia64/pci/pci.c)
        |
        +-> acpi_pci_irq_enable (drivers/acpi/pci_irq.c)
            |
            +-> iosapic_enable_intr (arch/ia64/kernel/iosapic.c)
                |
                +-> set_rte (arch_ia64/kernel/iosapic.c)

A following patch fixes this issue.