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From: Jung-uk Kim <jkim@FreeBSD.org>
To: John Baldwin <jhb@freebsd.org>
Date: Tue, 15 Mar 2011 17:14:14 -0400
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Cc: svn-src-head@freebsd.org, svn-src-all@freebsd.org,
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Subject: Re: svn commit: r219676 - head/sys/x86/x86
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On Tuesday 15 March 2011 05:01 pm, John Baldwin wrote:
> On Tuesday, March 15, 2011 3:47:20 pm Jung-uk Kim wrote:
> > Author: jkim
> > Date: Tue Mar 15 19:47:20 2011
> > New Revision: 219676
> > URL: http://svn.freebsd.org/changeset/base/219676
> >
> > Log:
> >   Do not let machdep.tsc_freq modify tsc_freq itself.  It is bad
> > for i386 as it does not operate atomically.  Actually, it serves
> > no purpose.
> >
> >   Noticed by:	bde
>
> Ouch,  please revert!   We have depended on this for testing to
> workaround BIOS issues (e.g. the USB SMI# handler firing at a bad
> time during boot causing the TSC frequency to be calculated
> incorrectly).  I agree it's a hack that this works, but it has
> actually proven useful in the past.

You can still change timecounter frequency.  Can you please explain 
why you need to change tsc_freq directly?

Jung-uk Kim