Messages in this thread | | | Date | Thu, 10 Jul 2008 11:02:25 +0100 | From | Alan Cox <> | Subject | Re: [PATCH] uio: uio_pdrv_genirq V2 |
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On Thu, 10 Jul 2008 12:30:36 +0200 Uwe Kleine-König <Uwe.Kleine-Koenig@digi.com> wrote:
> Alan Cox wrote: > > > > > > + else if (!irq_on && !priv->irq_disabled) > > > > + disable_irq(dev_info->irq); > > > I'm not sure if this is a problem on SMP. Should you use > > > disable_irq_nosync here, too? Probably it's OK. > > > > That one will also deadlock. > Can you explain why? I think irqcontrol is only called in task context. > I only see one possible deadlock and that's disable_irq being called > while the irq is IRQ_INPROGRESS on the same cpu. I'm always willing to > learn.
CPU0 (UIO IRQ) CPU1 (irqcontrol) take IRQ take spin lock spin on spinlock disable_irq (blocks)
> I think I didn't understand you right here, with the lock this can > happen, too, doesn't it?
Actually yes - so it would simplify it without changing behaviour.
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