From: Alexander Gordeev <lasaine@lvk.cs.msu.su>
To: john stultz <johnstul@us.ibm.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
LKML <linux-kernel@vger.kernel.org>,
Rodolfo Giometti <giometti@linux.it>,
Andrew Morton <akpm@linux-foundation.org>,
Ingo Molnar <mingo@elte.hu>
Subject: Re: [PATCH] pps: Make pps_gen_parport depend on BROKEN
Date: Tue, 22 Feb 2011 19:20:52 +0300 [thread overview]
Message-ID: <20110222192052.60039749@desktopvm.lvknet> (raw)
In-Reply-To: <1298064881.2431.3.camel@work-vm>
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Hi John,
В Fri, 18 Feb 2011 13:34:41 -0800
john stultz <johnstul@us.ibm.com> пишет:
> On Fri, 2011-02-18 at 22:16 +0100, Thomas Gleixner wrote:
> > This driver causes hard lockups, when the active clock soure is
> > jiffies. The reason is that it loops with interrupts disabled waiting
> > for a timestamp to be reached by polling getnstimeofday(). Though with
> > a jiffies clocksource, when that code runs on the same CPU which is
> > responsible for updating jiffies, then we loop in circles for ever
> > simply because the timer interrupt cannot update jiffies. So both UP
> > and SMP can be affected.
>
> Yuck.
>
> Alexander, Rodolfo: Instead of polling on gtod, could you take a
> timestamp, calculate the delay and then use udelay()?
Sure, it's possible but it would be less precise IMHO. I'll test it.
--
Alexander
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prev parent reply other threads:[~2011-02-22 16:21 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-02-18 21:16 [PATCH] pps: Make pps_gen_parport depend on BROKEN Thomas Gleixner
2011-02-18 21:34 ` john stultz
2011-02-22 16:20 ` Alexander Gordeev [this message]
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