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    SubjectRe: [RFC][2.6.12.3] IRQ compression/sharing patch
    On Sun, 14 Aug 2005, James Cleverdon wrote:

    > > > +static int next_irq = 16;
    > >
    > > Won't this need a lock for hotplug later?
    >
    > That's what I thought originally, but maybe not. We initialize all RTEs
    > and assign IRQs+vectors fairly early in boot, plus store the results in
    > arrays. Thereafter the functions just return the preallocated values.
    >
    > Hmmm... Since the I/O APIC init comes after the other CPUs are brought
    > online, and since I don't understand all that the MSI driver is trying
    > to accomplish, it might be safer to use a spin lock anyway.

    With respect to vector allocation, the MSI driver locks around
    assign_irq_vector, it doesn't look like next_irq is used in that path so
    you shouldn't need a lock if it's only used in single threaded init. This
    of course would change if IOAPICs were added after boot.

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