lkml.org 
[lkml]   [2008]   [Jul]   [10]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH] uio: uio_pdrv_genirq V2
Hello Alan,

Alan Cox wrote:
> 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)
Ah, OK, that's because uio_pdrv_genirq_handler and
uio_pdrv_genirq_irqcontrol share the lock.

Is this something that lockdep can detect?

Best regards and thanks for clearifying
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/

\
 
 \ /
  Last update: 2008-07-10 12:51    [from the cache]
©2003-2011 Jasper Spaans