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Subject: Re: Using sched_clock for mmio-trace
From: Thomas Gleixner <tglx@linutronix.de>
Reply-To: tglx@linutronix.de
To: Andi Kleen <andi@firstfloor.org>
Cc: "Frank Ch. Eigler" <fche@redhat.com>, Jeff Muizelaar <jeff@infidigm.net>,
       linux-kernel@vger.kernel.org
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Date: Sat, 17 Feb 2007 16:19:58 +0100
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On Sat, 2007-02-17 at 15:56 +0100, Andi Kleen wrote:
> > This is one of the reasons why we don't just use good old
> > do_gettimeofday(), since it takes locks and can lead to lock recursion
> > if parts of itself are probed.
> 
> do_gettimeofday doesn't take locks.
> 
> Only restriction is that you can't single step it with long 
> pauses between instructions.

Err, it uses read side of xtime lock, so you can not call it from a
place which write locks xtime lock.

	tglx