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Subject: Re: [tip:sched/core] cpu: Remove incorrect BUG_ON
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
To: Oleg Nesterov <oleg@redhat.com>
Cc: linux-tip-commits@vger.kernel.org, linux-kernel@vger.kernel.org,
        hpa@zytor.com, mingo@redhat.com, tglx@linutronix.de, mingo@elte.hu
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Date: Tue, 23 Nov 2010 18:16:08 +0100
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On Tue, 2010-11-23 at 16:08 +0100, Oleg Nesterov wrote:
> > Ah,. uhm,. you mean, not do anything at all?
> >
> > Dunno, really, let me try and read the code there.
> 
> Thanks. This is very minor of course, but it would be nice to
> undestand the reason. To me it looks unneeded, but I don't trust
> myself.  (snippets from my previous email below).
> 
> 
I think because the call to __cpu_die (-> native_cpu_die) relies on the
remote cpu running the idle thread, and the CPU_DEAD notifier callback
wants to run with the guarantee the remote cpu is in fact dead as a
doornail.