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    SubjectRe: [patch] io-apic-2.1.98-B

    On Sun, 26 Apr 1998, MOLNAR Ingo wrote:
    > here it breaks the NE2000 driver. (flood pinging causes interface hang,
    > this is because IRQs are lost with the counter-less approach)

    Quite frankly I think that anything that tries to count the interrupts is
    a buggy approach.

    That's not how the traditional APIC works either: it doesn't count
    interrupts when they are disabled. So if the NE2000 driver has problems
    then those are bugs in the NE2000 driver regardless of any io-apic stuff,
    and it is possible that it shows up with the io-apic only because of some
    subtle timing issues.

    And if you do only a "cli/sti" sequence, that doesn't count the number of
    interrupts that happened during the interrupts disabled, and you'll get
    only one interrupt when you enable them again.

    I'd rather fix the driver that is broken than have a system that has a
    unnecessarily complex in handling interrupts. We've had too many problems
    with interrupts under SMP for me to be willing to maintain hackish code
    that doesn't have any solid reason for existing.

    I'd like to have the self-IPI part, but I would _really_ really prefer to
    not have the counter, until somebody convices me that it has to be there
    (and that implies giving a reason other than "some ne2000 card has
    problems", because the problems you see sound like they might be problems
    for other people regardless of any io-apic issues).

    > I've added various comments to key pieces of the code. Probably we dont
    > need _that_ many counters, but i wanted to have stability first. With this
    > patch i claim that the IO-APIC code is correct, anything left to be done?

    I think you're going the wrong way. You're _adding_ stuff to make it
    stable, and then we'll never dare remove it. I'd much rather try to remove
    as much as humanly possible and fix any problems that uncovers rather than
    try to add barnacles that hide the problem.


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