From: Claudio Scordino <cloud.of.andor@gmail.com>
To: john stultz <johnstul@us.ibm.com>
Subject: Re: Bug: timer going backward on a dual core
Date: Sun, 30 Oct 2005 23:13:01 +0100
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Cc: kernelnewbies@nl.linux.org, linux-kernel@vger.kernel.org
References: <200510282109.42054.cloud.of.andor@gmail.com> <200510282339.16196.cloud.of.andor@gmail.com> <1130535889.27168.423.camel@cog.beaverton.ibm.com>
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> > > > > > We have a dual-core AMD64 with the new kernel 2.6.14 and the
> > > > > > timer goes backward...
> > > > > >
> > > > > >
> > > > > > CONFIGURATION:
> > > > > >
> > > > > > Kernel: 2.6.14
> > > > > > Distribution: Gentoo Linux 2005.0
> > > > > > Processor: Athlon 64 x2 4200+ (dual core)
> > > > > > Motherboard: Abit KN8
> > > > > > Memory: 1GB PC3200
> > > > > >
> > > > > >
> > > > > > PROBLEM:
> > > > > >
> > > > > > gettimeofday goes backward and returns values that are not
> > > > > > monotonic, giving values that are smaller than values returned
> > > > > > before.
> > > > > >
> > > > > > The system has been tested with timer as PIT, PIT/TSC and PM and
> > > > > > the problem occurs with all the configurations.
> > > > > >
> > > > > > Here is the config file that we used for the PM configuration.
> > > > > >
> > > > > > Any suggestion ?
> > > > >
> > > > > Booting w/ idle=poll tends to work around this issue. You might
> > > > > check with your motherboard vendor for an updated BIOS that
> > > > > supports HPET or the ACPI PM timer.
> > > >
> > > > We already updated the BIOS with the latest version.
> > > >
> > > > Also the booting command idle=poll doesn't work.
> > >
> > > Hmm. Not sure then. Is this a new regression on the same hardware?
> >
> > Yes, we tried with idle=poll and the problem occurred again.
>
> Sorry for the confusion, I meant if the problem is new to 2.6.14, or if
> it also happened with 2.6.13?

Sorry, I didn't understand. It happened also with the old versions of the 
kernel. The only temporary solution that we've found is to disable one 
processor :(

>
> > > Would you mind filing a bug (http://bugzilla.kernel.org )on this and
> > > attaching your config and dmesg there?
> >
> > Sure.
>
> Please assign it to me or add me to the cc list.

Done.

Thanks,

                Claudio
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