From: Ido Yariv <ido@wizery.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-kernel@vger.kernel.org
Subject: Re: [RFC] genirq: Flush the irq thread on synchronization
Date: Fri, 16 Dec 2011 12:48:28 +0200 [thread overview]
Message-ID: <20111216104828.GB18877@WorkStation> (raw)
In-Reply-To: <20111204190932.GO32400@WorkStation>
Hi Thomas,
On Sun, Dec 04, 2011 at 09:09:32PM +0200, Ido Yariv wrote:
> Hi Thomas,
>
> On Sat, Dec 03, 2011 at 12:21:46AM +0100, Thomas Gleixner wrote:
> > I can see your problem, but this might lead to threads_active leaks
> > under certain conditions. desc->threads_active was only meant to deal
> > with shared interrupts.
> >
> > We explicitely allow a design where the primary handler can leave the
> > device interrupt enabled and allow further interrupts to occur while
> > the handler is running. We only have a single bit to note that the
> > thread should run, but your wakeup would up the threads_active count
> > in that scenario several times w/o a counterpart which decrements it.
> >
> > The solution for this is to keep the current threads_active semantics
> > and make the wait function different. Instead of waiting for
> > threads_active to become 0 it should wait for threads_active == 0 and
> > the IRQTF_RUNTHREAD for all actions to be cleared. To avoid looping
> > over the actions, we can take a similar approach as we take with the
> > desc->threads_oneshot bitfield.
>
> Thanks for reviewing this.
>
> I might be missing something, but I don't see any potential
> threads_active leaks in this approach. We wont increase threads_active
> if IRQTF_RUNTHREAD was already set beforehand (as test_and_set_bit()
> will return 1).
>
> If irq_wake_thread is called multiple times before irq_thread has had a
> chance to run, threads_active will only be increased once and decreased
> back when IRQTF_RUNTHREAD is cleared.
>
> Am I missing something? If not, do you see any other issues with this
> implementation?
Any thoughts on this?
Thanks,
Ido.
next prev parent reply other threads:[~2011-12-16 10:48 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-02 16:24 [RFC] genirq: Flush the irq thread on synchronization Ido Yariv
2011-12-02 23:21 ` Thomas Gleixner
2011-12-04 19:09 ` Ido Yariv
2011-12-16 10:48 ` Ido Yariv [this message]
2012-02-13 9:43 ` Ido Yariv
2012-02-15 14:34 ` Thomas Gleixner
2012-03-01 10:54 ` Ido Yariv
2011-12-05 21:55 ` Thomas Gleixner
2011-12-06 23:28 ` Ido Yariv
2011-12-07 0:48 ` Thomas Gleixner
2011-12-07 8:21 ` Ido Yariv
2012-03-14 11:07 ` [tip:irq/core] " tip-bot for Ido Yariv
2012-03-15 19:07 ` Alexander Gordeev
2012-03-15 19:27 ` Thomas Gleixner
2012-03-15 22:59 ` Ido Yariv
2012-03-16 10:06 ` Thomas Gleixner
2012-03-16 10:34 ` [tip:irq/core] genirq: Remove paranoid warnons and bogus fixups tip-bot for Thomas Gleixner
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