Messages in this thread | | | Date | Thu, 10 Jul 2008 12:30:36 +0200 | From | Uwe Kleine-König <> | Subject | Re: [PATCH] uio: uio_pdrv_genirq V2 |
| |
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.
> The easiest fix is probably to use test_and_set and friends for each I/O > operation. Actually using spinlock + irq_disabled variable is new in V2 of this patch. Don't know why this changed, though.
> You would then not need the lock to protect ->irq_disabled. > Propogating that throughout means your user space has to handle the case > of an IRQ arriving after disable returns but would be a fair bit saner I > think ? I think I didn't understand you right here, with the lock this can happen, too, doesn't it?
Best regards Uwe
-- Uwe Kleine-König, Software Engineer Digi International GmbH Branch Breisach, Küferstrasse 8, 79206 Breisach, Germany Tax: 315/5781/0242 / VAT: DE153662976 / Reg. Amtsgericht Dortmund HRB 13962 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |