linux-kernel - Re: [Regression] Negative time on Acer Ferrari One with current -git

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Message-Id: <201005222320.01506.rjw@sisk.pl>
Date:	Sat, 22 May 2010 23:20:01 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Thomas Gleixner <tglx@...utronix.de>,
	John Stultz <johnstul@...ibm.com>
Cc:	Linus Torvalds <torvalds@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [Regression] Negative time on Acer Ferrari One with current -git

On Saturday 22 May 2010, Rafael J. Wysocki wrote:
> On Saturday 22 May 2010, Thomas Gleixner wrote:
> > On Sat, 22 May 2010, Thomas Gleixner wrote:
> > 
> > > On Sat, 22 May 2010, Rafael J. Wysocki wrote:
> > > > On Saturday 22 May 2010, Thomas Gleixner wrote:
> > > > 
> > > > > Also which clocksource is used ?
> > > > 
> > > > hpet
> > > 
> > > Hmm, there is only one hpet related commit sin .34:  30a564be9d
> > > and I can hardly see how this should be related.
> > 
> > Does the problem persist if you disable HPET on the kernel command line ?
> 
> I didn't try that, but I bisected it in the meantime which lead to:
> 
> commit 64ce4c2f5252f25798117fa80a027993163d6d84
> Author: John Stultz <johnstul@...ibm.com>
> Date:   Thu Mar 11 14:04:47 2010 -0800
> 
>     time: Clean up warp_clock()
> 
>     warp_clock() currently accesses timekeeping internal state directly, which
>     is unnecessary.  Convert it to use the proper timekeeping interfaces.
> 
>     Signed-off-by: John Stultz <johnstul@...ibm.com>
>     Cc: Ingo Molnar <mingo@...e.hu>
>     Signed-off-by: Andrew Morton <akpm@...ux-foundation.org>
>     Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> 
> So I don't think it's an hpet issue. :-)
> 
> I'm now going to revert that commit and see what happens.

After reverting commit 64ce4c2f above things work again.

To be precise, I reverted both commit 64ce4c2f and commit 6a867a3 (time: 
Remove xtime_cache), but since the symptoms continued to apprear after
reverting the latter alone, it's quite clear that commit 64ce4c2f breaks things
on this box.

Thanks,
Rafael
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