linux-kernel - Re: regression from softlockup fix

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Message-ID: <20071119190356.GC12650@elte.hu>
Date:	Mon, 19 Nov 2007 20:03:56 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	David Miller <davem@...emloft.net>, linux-kernel@...r.kernel.org,
	gregkh@...e.de, Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: regression from softlockup fix


* Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> I thought the timer code kicked the watchdog after waking up after a 
> long sleep anyway?  At one point I was looking into a mechanism to 
> temporarily disable the watchdog during a wait for a timer event, but 
> it got complex - and I thought - unnecessary.
> 
> Specifically this in kernel/time/timekeeping.c:
> 
> 		/*
> 		 * When we are idle and the tick is stopped, we have to touch
> 		 * the watchdog as we might not schedule for a really long
> 		 * time. This happens on complete idle SMP systems while
> 		 * waiting on the login prompt. We also increment the "start of
> 		 * idle" jiffy stamp so the idle accounting adjustment we do
> 		 * when we go busy again does not account too much ticks.
> 		 */
> 		if (ts->tick_stopped) {
> 			touch_softlockup_watchdog();
> 			ts->idle_jiffies++;
> 		}
> 
> Or does this happen on the sleep path?  If so, wouldn't the right fix 
> to be this on the wakeup path?

yep, i guess this would do the trick. David, could you try it perhaps 
(let me know if i should make a patch for you).

	Ingo
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