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SubjectRe: 2.4.18 Preempt Freezeups
Date
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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