Re: Calling current() from interrupt context

From: Andi Kleen (
Date: Mon Oct 09 2000 - 17:55:33 EST

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 ?


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