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    SubjectRe: [PATCH] Prevent nested interrupts when the IRQ stack is near overflowing v2

    * Linus Torvalds <torvalds@linux-foundation.org> wrote:

    [...]
    >
    > Now, it's also true that our IRQ infrastructure handlers _could_ be smarter,
    > and make the whole problem less likely to happen.
    >
    > In particular, it's probably true that especially on modern hardware with
    > multiple cores, and especially when you do _not_ have irq sharing (which is
    > the common case these days for things like network drivers that can use
    > MSI), we really would be better off having the irq disabled over the whole
    > thing, and on some interrupt controllers it might even be worth it to do the
    > old optimization of not masking-and-acking, but just acking.

    Yes.

    > But see above. This is _not_ something that a driver can do any more. They
    > don't know whether the interrupt might end up being shared. Just blindly
    > setting IRAF_DISABLED in a driver is _not_ the answer. But being smarter in
    > the generic irq handler code might work.
    >
    > And then, what we could do, is to mark the drivers that absolutely _must_ be
    > able to nest specially. Like the IDE driver when in PIO mode. Or maybe the
    > SCSI drivers, if they still depend on that timer interrupt happening while
    > they are busy.

    I think the patch as posted solves a real problem, but also perpetuates a bad
    situation.

    At minimum we should print a (one-time) warning that some badness occured.
    That would push us either in the direction of improving drivers, or towards
    improving the generic code.

    Thanks,

    Ingo


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