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Re: [PATCH v2 6/6] stop_machine: kill stop_cpus_lock and lg_double_lock/unlock()

From	Peter Zijlstra <peterz@infradead.org>
Newsgroups	linux.kernel
Subject	Re: [PATCH v2 6/6] stop_machine: kill stop_cpus_lock and lg_double_lock/unlock()
Date	2015-08-02 00:40 +0200
Message-ID	<pSNBD-1yt-1@gated-at.bofh.it> (permalink)
References	<pOLoJ-JK-9@gated-at.bofh.it> <pOLoK-JK-21@gated-at.bofh.it> <pS41Q-2wU-13@gated-at.bofh.it> <pSCGe-2sX-11@gated-at.bofh.it>
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On Sat, Aug 01, 2015 at 12:57:18PM +0200, Oleg Nesterov wrote:

> > > +	if (stop_work_pending(stopper1) != stop_work_pending(stopper2))
> > > +		goto unlock;
> >
> > You could DoS/false positive this by running stop_one_cpu() in a loop,
> > and thereby 'always' having work pending on one but not the other.
> 
> IIRC no. I am pretty sure stop_one_cpu() doesn't use stopper->stop_work,
> only stop_machine() does.

Urgh, I missed you were testing the cpu_stopper::stop_work not the
cpu_stopper::works list.


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Re: [PATCH v2 6/6] stop_machine: kill stop_cpus_lock and  lg_double_lock/unlock() Oleg Nesterov <oleg@redhat.com> - 2015-08-01 13:00 +0200
  Re: [PATCH v2 6/6] stop_machine: kill stop_cpus_lock and  lg_double_lock/unlock() Peter Zijlstra <peterz@infradead.org> - 2015-08-02 00:40 +0200

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