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    SubjectRe: [PATCH RT] ehea: make receive irq handler non-threaded (IRQF_NODELAY)
    On Thu, 20 May 2010, Jan-Bernd Themann wrote:
    > > > Thought more about that. The case at hand (ehea) is nasty:
    > > >
    > > > The driver does _NOT_ disable the rx interrupt in the card in the rx
    > > > interrupt handler - for whatever reason.
    > >
    > > Yeah I saw that, but I don't know why it's written that way. Perhaps
    > > Jan-Bernd or Doug will chime in and enlighten us? :)
    >
    > From our perspective there is no need to disable interrupts for the
    > RX side as the chip does not fire further interrupts until we tell
    > the chip to do so for a particular queue. We have multiple receive

    The traces tell a different story though:

    ehea_recv_irq_handler()
    napi_reschedule()
    eoi()
    ehea_poll()
    ...
    ehea_recv_irq_handler() <---------------- ???
    napi_reschedule()
    ...
    napi_complete()

    Can't tell whether you can see the same behaviour in mainline, but I
    don't see a reason why not.

    > queues with an own interrupt each so that the interrupts can arrive
    > on multiple CPUs in parallel. Interrupts are enabled again when we
    > leave the NAPI Poll function for the corresponding receive queue.

    I can't see a piece of code which does that, but that's probably just
    lack of detailed hardware knowledge on my side.

    Thanks,

    tglx


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