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    SubjectRe: Calling current() from interrupt context
    On Mon, Oct 09, 2000 at 11:45:18PM +0100, Kenn Humborg wrote:
    > Simple. Each interrupt stack is, say, 8 pages. You have an array
    > of N interrupt stacks. Then you calculate
    >
    > cpu_id = (sp & ~(INT_STACK_SIZE-1)) >> (PAGE_SHIFT + 3);
    >
    > Actually, I'd put the interrupt stack and any other per-cpu data
    > structures together in this region.


    So your smp_processor_id() looks like:

    #define smp_processor_id() \
    (in_interrupt() ? (sp & ~(INT_STACK_SIZE-1)) >> (PAGE_SHIFT + 3) :
    (struct task_struct *)(sp & -8192)->current_cpu)


    ?

    There is just an ugly problem: in_interrupt already requires the CPU id
    to look up the table of interrupt counters.

    Now you could change the code to use interrupt_processor_id() and
    usermode_processor_id(), but what would you do in code which can
    be executed in both ?

    -Andi

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