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    SubjectRe: RT-Linux and SMP

    On Thu, 24 Apr 1997, Victor Yodaiken wrote:
    > Sure. But you are permitting two interrupts to execute at the same time
    > as long as neither invokes cli. So what prevents those two routines from
    > modifying each others data? If interrupt routines executing in non-cli
    > mode can modify shared data, wouldn't this cause a problem for SMP and
    > even in the single processor case?

    Two interrupts can run at the same time even under UP ("same time" in a
    very limited sense, obviously - but one interrupt can interrupt the
    other). As such, if we are ever in a critical section where this makes a
    difference, that critical section obviously has to do a cli/sti.

    And they do.

    > In any event, I think that the rtlinux soft-interrupts fits into this
    > scheme quite well and should make the irq_lock unecessary.

    I don't believe you can make the irq_lock unnecessary - _something_ like
    that is needed anyway.


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