Message-ID: <Pine.LNX.4.58.0710271203170.28617@gandalf.stny.rr.com>
Date:	Sat, 27 Oct 2007 12:05:44 -0400 (EDT)
From:	Steven Rostedt <rostedt@...dmis.org>
To:	Rui Nuno Capela <rncbc@...bc.org>
cc:	linux-rt-users@...r.kernel.org, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	Gregory Haskins <ghaskins@...ell.com>
Subject: Re: 2.6.23-rt4 (was 2.6.23-rt1 trouble)

--

On Sat, 27 Oct 2007, Rui Nuno Capela wrote:

> > On Mon, October 15, 2007 11:49, Rui Nuno Capela wrote:
> >>
> >> I am experiencing some highly annoying but intermitent freezing on a
> >> pentium4 2.80G HT/SMT box, when doing normal desktop work with 2.6.23-rt1.
> >>
> >>
> >> The same crippling behavior does not occur on a Core 2 Due T7200 2.0G
> >> SMP, so I suspect it's something due specific to the SMT scheduling
> >> support (Hyper-Threading). But can't tell for sure, obviously :)
> >>
> >
> > I was wrong. After several trials the same behavior also occurs on the
> > Core2 Duo T7200. It just took longer to show its nasty.
> >
> >
> >> The symptoms are noticeable primarily as some X/GUI intermitent freezing,
> >> sometimes only one application, then several and ultimately the whole X
> >> desktop becomes completely unresponsive. It looks like scheduling

When things start to freeze, could you capture the output of a sysrq-t.


> >> problems. There is this hint that switching to a spare console terminal
> >> (via Ctrl+Alt+Fn) might cause later recovery. But its just a question of
> >> some more time for it just happens again and again, one after another,
> >> several applications becoming temporarily frozen and just by luck the
> >> system gets back to normal, probably due to some incidental shake-up :)
> >> but there are other times that nothing seems to help with no alternative
> >> to the power-reset switch.
> >>
> >> I could not find any evidence on dmesg or in the system logs, of any
> >> apparent trouble. No BUGs, no oops, no panics, no nothing. It just
> >> freezes, this and that, now and then. It just makes it all unworkable
> >> and obviously subject to ditching.
> >>
> >> Again, this only happens on this P4/HT box. On a Core2 Duo laptop, with
> >> same 2.6.23-rt1 with the very same kernel configuration, it does not show
> >> any illness and is running quite fine.
> >>
> >
> > False. It used to run fine, until the creeps happen first time :(
> >
> >
> >> Remember one report I had about a similar freezing behavior? Now it's
> >> happening the other way around: the core2 is OK, the pentium4 is KO.
> >>
> >
> > Now it applies to all 2.6.23-rt1 images I could test upon.
> >
> >
> >> One naive suspicion goes like the new rcu-preempt code is to blame, since
> >> I don't remember having this or any other trouble with 2.6.23-rc8-rt1.
> >>
> >
> > Not be sure anymore, but this seems to be still a valid assumption.
> >
>
> just to let you know that still the same trouble persists with 2.6.23.1-rt4
>
> .config can be found here:
>    http://www.rncbc.org/datahub/config-2.6.23.1-rt4.0
>

I have a P4HT laptop (unfortunately with no serial). I use it as one of my
main machines, so it will suck for me when it freezes ;-). I'll take your
config and try it out.

I'll most likely do this on Monday since process Wife has the highest
priority over the weekend ;-)

-- Steve

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