linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Yong Zhang <yong.zhang0@gmail.com>
To: "Lothar Waßmann" <LW@KARO-electronics.de>
Cc: linux-kernel@vger.kernel.org,
	linux-arm-kernel@lists.infradead.org,
	Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [BUG] genirq: Race condition in ONESHOT IRQ handler disabling IRQ forever
Date: Tue, 7 Feb 2012 20:34:55 +0800	[thread overview]
Message-ID: <20120207123455.GA2452@zhy> (raw)
In-Reply-To: <20272.63074.235023.783459@ipc1.ka-ro>

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

  reply	other threads:[~2012-02-07 12:35 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-02-06  8:14 [BUG] genirq: Race condition in ONESHOT IRQ handler disabling IRQ forever =?utf-8?Q?Lothar_Wa=C3=9Fmann?=
2012-02-06 10:42 ` Lars-Peter Clausen
2012-02-07  9:03 ` Yong Zhang
2012-02-07 10:01   ` Lothar Waßmann
2012-02-07 12:34     ` Yong Zhang [this message]
2012-02-07 12:52       ` Lothar Waßmann
2012-02-07 13:07         ` Lars-Peter Clausen
2012-02-07 13:38           ` [PATCH] genirq: Fix race condition in ONESHOT irq handler Lothar Waßmann
2012-02-07 17:03             ` Thomas Gleixner
2012-02-08  6:05               ` Lothar Waßmann
2012-02-08 10:38                 ` Thomas Gleixner
2012-02-09  8:40                   ` Lothar Waßmann

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=20120207123455.GA2452@zhy \
    --to=yong.zhang0@gmail.com \
    --cc=LW@KARO-electronics.de \
    --cc=linux-arm-kernel@lists.infradead.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=tglx@linutronix.de \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).