lkml.org 
[lkml]   [2012]   [Feb]   [7]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [BUG] genirq: Race condition in ONESHOT IRQ handler disabling IRQ forever
    On Tue, Feb 07, 2012 at 11:01:06AM +0100, Lothar Waßmann wrote:
    > Hi,
    >
    > > On Mon, Feb 06, 2012 at 09:14:47AM +0100, Lothar Waßmann wrote:
    > > > Hi,
    > > >
    > > > I already sent this to <linux-kernel@vger.kernel.org> on Feb. 1, 2012
    > > > but did not get any response there. So resending to a wider audience
    > > > with improved subject line:
    > > >
    > > > there is a race condition in the threaded IRQ handler code for oneshot
    > > > interrupts that may lead to disabling an IRQ indefinitely. IRQs are
    > > > masked before calling the hard-irq handler and are unmasked only after
    > > > the soft-irq handler has been run. Thus if the hard-irq handler
    > > > returns IRQ_HANDLED instead of IRQ_WAKE_THREAD, meaning the soft-irq
    > > > will not be called, the interrupt will remain masked forever.
    > > >
    > > > This can happen due to a short pulse on the interrupt line, that
    > > > triggers the interrupt logic, but goes undetected by the hard-irq
    > > > handler. The problem can be reproduced with the TSC2007 touch
    > > > controller driver that uses ONESHOT interrupts.
    > >
    > > Isn't it the responsibility of the driver (say TSC2007)?
    > >
    > > In this case, TSC2007 should return IRQ_WAKE_THREAD IMHO.
    > >
    > That would mean it had to return IRQ_WAKE_THREAD unconditionally
    > making the return code useless.
    > And it would cause an extra useless loop through the softirq
    > handler.

    Yeah, it's the default behavior when we introduce 'theadirqs',
    and it's safe.

    You know in your patch unmask_irq() is called locklessly and
    it will introduce other race.

    Thanks,
    Yong
    --
    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: 2012-02-07 13:37    [W:0.021 / U:30.708 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site