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From: Alok Kataria <akataria@vmware.com>
To: Ingo Molnar <mingo@elte.hu>
Cc: the arch/x86 maintainers <x86@kernel.org>,
	LKML <linux-kernel@vger.kernel.org>,
	Zach Amsden <zach@vmware.com>
Subject: Re: x86, vmi: TSC going backwards check in vmi clocksource
Date: Thu, 19 Feb 2009 10:03:58 -0800	[thread overview]
Message-ID: <1235066638.23293.7.camel@alok-dev1> (raw)
In-Reply-To: <20090219111822.GN2354@elte.hu>

On Thu, 2009-02-19 at 03:18 -0800, Ingo Molnar wrote:
> * Alok Kataria <akataria@vmware.com> wrote:
> 
> > From: Alok N Kataria <akataria@vmware.com>
> > 
> > Similar to the check for TSC going backwards in the TSC 
> > clocksource, we also need this check for VMI clocksource.
> 
> ok. Precisely what kind of bug/symptoms does this fix?

If the read CYCLES_REAL counter value is less than the cycle_last value,
it may result in time jumps.
I also saw some messages about  process being stuck for more than
120sec, which was traced back to this.

Thanks,
Alok
> 
> 	Ingo


  reply	other threads:[~2009-02-19 18:04 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-02-18 20:33 x86, vmi: TSC going backwards check in vmi clocksource Alok Kataria
2009-02-19 11:18 ` Ingo Molnar
2009-02-19 18:03   ` Alok Kataria [this message]
2009-02-19 18:11     ` Ingo Molnar
2009-02-20 17:58 ` Ingo Molnar
2009-02-20 18:23   ` Alok Kataria
2009-02-20 18:31     ` Ingo Molnar

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