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From: Daniel Phillips <phillips@bonn-fries.net>
To: yodaiken@fsmlabs.com, Daniel Phillips <phillips@bonn-fries.net>
Subject: Re: 2.4.18 Preempt Freezeups
Date: Sun, 17 Mar 2002 02:14:14 +0100
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Cc: yodaiken@fsmlabs.com, Robert Love <rml@tech9.net>,
        Mikael Pettersson <mikpe@csd.uu.se>,
        linux kernel <linux-kernel@vger.kernel.org>
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On March 17, 2002 02:13 am, yodaiken@fsmlabs.com wrote:
> On Sun, Mar 17, 2002 at 01:33:04AM +0100, Daniel Phillips wrote:
> > On March 16, 2002 01:40 am, yodaiken@fsmlabs.com wrote:
> > > 
> > > Without preempt:
> > > 	x = movefrom processor register;
> 		// if preemption is on, we can be preempted and restart
> 		// on another processor so x will be wrong
> > >         do_something with x
> > > 
> > > is safe in SMP
> > > With [preempt] it requires a lock.
> > 
> > It must be a trick question.  Why would it?
> 
> See comment.

Which processor register were you thinking of?  Surely not anything in the 
general register set, and otherwise, it's just another example of per-cpu 
data.  It needs to be protected, and the protection is lightweight.

-- 
Daniel
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