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    SubjectRe: [RFC][PATCH -rt] irqd starvation on SMP by a single process?

    * Steven Rostedt <rostedt@goodmis.org> wrote:

    > On Fri, 12 May 2006, Ingo Molnar wrote:
    >
    > > ah. This actually uncovered a real bug. We were calling __do_softirq()
    > > with interrupts enabled (and being preemptible) - which is certainly
    > > bad.
    >
    > Hmm, I wonder if this is also affecting Mark's problem.
    >
    > But since I showed that if hardirqs_disabled and running PREEMPT not
    > PREEMPT_RT, disable_irq can call schedule. This is done in
    > drivers/net/3c59x.c. It has a watchdog timeout calling disable_irq,
    > which calls synchronize_irq which might schedule:
    >
    > void synchronize_irq(unsigned int irq)
    > {
    > struct irq_desc *desc = irq_desc + irq;
    >
    > if (irq >= NR_IRQS)
    > return;
    >
    > if (hardirq_preemption && !(desc->status & IRQ_NODELAY))
    > wait_event(desc->wait_for_handler,
    > !(desc->status & IRQ_INPROGRESS));
    > else
    > while (desc->status & IRQ_INPROGRESS)
    > cpu_relax();
    > }
    >
    > -- Steve
    >
    > >
    > > this was hidden before because the smp_processor_id() debugging code
    > > handles tasks bound to a single CPU as per-cpu-safe.
    > >
    > > could you check the (totally untested) patch below and see if that fixes
    > > things for you? I've also added your affinity change.
    > >
    -
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