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    SubjectRe: [patch] IDE problems on SMP, fixed? (fwd)

    On Wed, 29 Jul 1998, Linus Torvalds wrote:

    > > Between the two places we only have a couple of non-functional if()'s
    > > and assignments to static variables on the stack.
    > Note that it looks like Ingo by mistake removed the ide__sti completely:

    no it was completely intentional :)

    > and note how "DISK_RECOVERY_TIME" is usually defined to be zero unless
    > explicitly asked to be something else. So the place Ingo moved it to will
    > never even be compiled into the kernel, so the interrupt enable is never
    > done.
    > Ingo, if you can reproduce this consistantly, I'd suggest moving the sti
    > down to a place where it actually triggers, until you find the place where
    > it really fixes the problem..

    yes i've been doing this for the last 2 hours :) _so far_ it looks like if
    we _ever_ enable interrupts 'within' that critical ide.c part, i get a
    lockup sooner or later. I've moved the sti down and out of start_request,
    until the next place where we disable IRQs again, and lockups always. The
    only case where i got no lockup was when i removed the sti completely.

    it might be unrelated, but that part of ide.c was always very critical,
    similar to ne.c, as it enables/disables itself from within an IRQ handler,
    this used to pop up more subtle IOAPIC bugs. but this one does not look
    like the typical IRQ deadlock.

    i've also double-checked that other system parameters are invariant:
    replacing the ide_sti() by a cli (same length instruction, almost the same
    timings, very same cache layout), but no lockup. various BIOS settings
    make no difference.

    -- mingo

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