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    SubjectRe: kernel-hacking-HOWTO: An lk primer seeks feedback
    >>>>> "Werner" == Werner Almesberger <> writes:

    Werner> Paul Rusty Russell wrote:
    >> `This document describes the common routines, locking systems and
    >> general requirements for kernel code: its goal is to serve as a
    >> primer for Linux kernel development.'

    Werner> 5.2: you may want to
    Werner> discuss disable_irq, disable_irq_nosync, and enable_irq. On
    Werner> most (all?) architectures, they are reasonably inexpensive
    Werner> ways to block specific interrupts. (BTW, why don't we actually
    Werner> have some kind of interrupt blocking that doesn't go down to
    Werner> the interrupt controller hardware ? Is the PIC part considered
    Werner> to be cheap enough in all possible cases ?)

    Actually I think the discussion of disable_irq/enable_irq should say
    something along the lines of "don't use these, if you think you need
    them, think again, if you still think you need them, think again real

    enable_irq/disable_irq are quite expensive and should not be used
    except for very special cases. I'd claim that 99.9% of the time people
    are better off disabling interrupts directly on the device (most sane
    hardware has a bit to disable it) or using spin locks.


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