linux-kernel - Re: [ANNOUNCE] 2.6.29.6-rt23

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Date:	Fri, 10 Jul 2009 17:17:26 -0700
From:	Fernando Lopez-Lezcano <nando@...ma.Stanford.EDU>
To:	Thomas Gleixner <tglx@...utronix.de>
Cc:	nando@...ma.Stanford.EDU, LKML <linux-kernel@...r.kernel.org>,
	rt-users <linux-rt-users@...r.kernel.org>,
	Ingo Molnar <mingo@...e.hu>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Carsten Emde <ce@...g.ch>,
	Clark Williams <williams@...hat.com>,
	Frank Rowand <frank.rowand@...sony.com>,
	Robin Gareus <robin@...eus.org>,
	Gregory Haskins <ghaskins@...ell.com>,
	Philippe Reynes <philippe.reynes@...smpp.fr>,
	Will Schmidt <will_schmidt@...t.ibm.com>,
	Darren Hart <dvhltc@...ibm.com>, Jan Blunck <jblunck@...e.de>,
	Sven-Thorsten Dietrich <sdietrich@...ell.com>,
	Jon Masters <jcm@...hat.com>
Subject: Re: [ANNOUNCE] 2.6.29.6-rt23

On Fri, 2009-07-10 at 20:29 +0200, Thomas Gleixner wrote:
> On Fri, 10 Jul 2009, Fernando Lopez-Lezcano wrote:
> > On Thu, 2009-07-09 at 20:25 +0200, Thomas Gleixner wrote:
> > > We are pleased to announce the next update to our new preempt-rt
> > > series.
> > >  
> > >      - update to 2.6.29.6
> > >  
> > >      - compile fixes (Wu Zhangjin)
> > > 
> > >      - powerpc highmem fix
> > > 
> > >      - hwlat smp_processor_id() fix (Carsten)
> > > 
> > >      - ktime_get* speedups (Martin)
> > 
> > I'm getting slightly weird behavior from rt23 in an intel quad core
> > machine (my T61 laptop is fine), rt22 was fine. It is some timer issue,
> > if I type continuously I get (every few seconds) repeated keys. Nothing
> > in the logs, nothing in dmesg that is (significantly) different from an
> > rt22 boot. 
> 
> Hmm. The only change which touches timer related stuff is the ktime*
> speedups. Can you please apply the revert patch below and check
> whether that changes anything? If not, then we need to look at the
> 2.6.29.5 -> .6 delta.

The bad behavior is gone with the patch reverted. 

But life is not so simple :-) 

I rebooted into the newer kernel and the problem was gone. Then I
rebooted into the older (unreverted) kernel and the problem was not
there either! Sigh. Then I powered down the machine, powered up in the
older kernel and the problem was there. Powered down, powered up in the
newer kernel and the problem was gone. Warm boot into the older kernel
and the problem is _not_ there. So it would seem there's something
getting screwed up at the hardware level that the reverted patch
"fixes"...

When the problem happens it is very obvious. And also affects the
screensaver, of course. I don't see it in my laptop and on another P4
based machine running fc11 (as opposed to fc10 in the others) and a
different build. 

Thanks!
-- Fernando


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