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From: john stultz <johnstul@us.ibm.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Alexander Gordeev <lasaine@lvk.cs.msu.su>,
	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: Fri, 18 Feb 2011 13:34:41 -0800	[thread overview]
Message-ID: <1298064881.2431.3.camel@work-vm> (raw)
In-Reply-To: <alpine.LFD.2.00.1102182214190.2701@localhost6.localdomain6>

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()?

thanks
-john



  reply	other threads:[~2011-02-18 21:34 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 [this message]
2011-02-22 16:20   ` Alexander Gordeev

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