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    SubjectRe: 2.6.19-rc5: known regressions :SMP kernel can not generate ISA irq
    On Mon, 2006-11-13 at 10:11 -0700, Eric W. Biederman wrote:
    > > So when you "mask" an edge-triggered IRQ, you can't really mask it
    > at all,
    > > because if you did that, you'd lose it forever if the IRQ comes in
    > while
    > > you masked it. Instead, we're supposed to leave it active, and set a
    > flag,
    > > and IF the IRQ comes in, we just remember it, and mask it at that
    > point
    > > instead, and then on unmasking, we have to replay it by sending a
    > > self-IPI.
    > >
    > > Maybe that part got broken by some of the IRQ changes by Eric.
    > Hmm. The other possibility is that this is a genirq migration issue.
    > Yep. That looks like it. In the genirq migration the edge and
    > level triggered cases got merged and previously disable_edge_ioapic
    > was a noop. Ouch.

    hm, that should be solved by the generic edge-triggered flow handler as
    well: we never mask an IRQ first time around, we only mask it if
    we /already/ have the 'soft' IRQ_PENDING flag set. (in that case the
    lost edge is not an issue because we have the information already - and
    the masking will prevent a screaming edge source)

    but maybe this concept has not been pushed through to the disable/enable
    irq logic itself? (it's only present in the flow handler) Thomas, do you


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      Last update: 2006-11-13 21:49    [W:0.019 / U:31.264 seconds]
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