linux-kernel - Re: [patch 1/4] Ignore stolen time in the softlockup watchdog

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Message-Id: <20070424113222.ed2e1314.akpm@linux-foundation.org>
Date:	Tue, 24 Apr 2007 11:32:22 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
Cc:	Ingo Molnar <mingo@...e.hu>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	virtualization@...ts.osdl.org, Prarit Bhargava <prarit@...hat.com>,
	Eric Dumazet <dada1@...mosbay.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	john stultz <johnstul@...ibm.com>,
	Zachary Amsden <zach@...are.com>,
	James Morris <jmorris@...ei.org>,
	Dan Hecht <dhecht@...are.com>,
	Paul Mackerras <paulus@...ba.org>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Chris Lalancette <clalance@...hat.com>,
	Rick Lindsley <ricklind@...ibm.com>, Andi Kleen <ak@...e.de>
Subject: Re: [patch 1/4] Ignore stolen time in the softlockup watchdog

On Tue, 24 Apr 2007 11:16:09 -0700 Jeremy Fitzhardinge <jeremy@...p.org> wrote:

> Andrew Morton wrote:
> > I said that because the damn thing went away when I was hunting it down
> > because I lost the config and was unable to remember the right combination
> > of debug settings.  Fortunately it later came back so I took care to
> > preserve the config.
> >   
> 
> sched_clock doesn't *do* anything except flap interrupts.

Well, it _is_ mysterious.

Did you try to locate the code which failed?  I got lost in macros and
include files, and gave up very very easily.  Stop hiding, Ingo.

> Oh, wait, have
> you got Andi's bugfixed version of the sched_clock patch?  The first
> version did a local_save_flags rather than a local_irq_save.

I have whatever I pulled from firstfloor over the weekend.  It's in
rc7-mm1.  No, it doesn't use local_save_flags.

> >> Hm, is it caused by using sched_clock() to generate the printk
> >> timestamps while generating the lock test output?
> >>     
> >
> > Conceivably.  What does that locking API test do?
> >   
> 
> Didn't make a difference here.  Building your config now.
> 
> > I was using printk timestamps and netconsole at the time.
> >   
> 
> Ah, great, now you're going to make me setup netconsole...
> 

That's a doddle.

On test system, boot with

netconsole=4444@<test-system-ip-addr>/eth0,<udp-port-no>@<workstation-ip-addr>/<workstation-mac-addr>

On workstation:

sudo netcat -u -l -p <udp-port-no> | tee -a ~/.log/log-<test-system-hostname>
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