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Date:      Wed, 9 May 2007 15:43:32 -0400
From:      John Baldwin <jhb@freebsd.org>
To:        "Attilio Rao" <attilio@freebsd.org>
Cc:        Perforce Change Reviews <perforce@freebsd.org>, Rui Paulo <rpaulo@freebsd.org>
Subject:   Re: PERFORCE change 119371 for review
Message-ID:  <200705091543.33002.jhb@freebsd.org>
In-Reply-To: <3bbf2fe10705091233t405121d2qda9a058ecf4124bc@mail.gmail.com>
References:  <200705062110.l46LAZqE011583@repoman.freebsd.org> <200705091457.39167.jhb@freebsd.org> <3bbf2fe10705091233t405121d2qda9a058ecf4124bc@mail.gmail.com>

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On Wednesday 09 May 2007 03:33:11 pm Attilio Rao wrote:
> 2007/5/9, John Baldwin <jhb@freebsd.org>:
> > On Sunday 06 May 2007 05:10:35 pm Rui Paulo wrote:
> > > http://perforce.freebsd.org/chv.cgi?CH=119371
> > >
> > > Change 119371 by rpaulo@rpaulo_epsilon on 2007/05/06 21:10:15
> > >
> > >       We don't need any scheduler support because:
> > >       1) msrtemp is a child of cpu - this implies that every
> > >          rdmsr/cpuid instruction will be executed on that CPU.
> >
> > No, that isn't true.  You do need to use sched_bind() for that so you are
> > really on the desired CPU when you read the MSR.
> 
> I think he just needs msr of the cpu where curthread is executed, so
> any scheduler lock should be needed.
> If he needs to know msr of a particular CPU he really needs so, but it
> doesn't seem the case.

The sysctl is per-CPU, so he needs the msr from a specific CPU in the sysctl 
handler.  I.e., it's like dev.cpu.0.temp or some such.

-- 
John Baldwin



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