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Date: Mon, 23 Mar 2015 09:55:23 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Wanpeng Li <wanpeng.li@linux.intel.com>, Juri Lelli <juri.lelli@arm.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH RESEND v10] sched/deadline: support dl task migration
 during cpu hotplug
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On Mon, Mar 23, 2015 at 08:25:04AM +0100, Ingo Molnar wrote:
> > >> >> >> +			if (cpu >= nr_cpu_ids) {
> > >> >> >> +				if (dl_bandwidth_enabled()) {
> > >> >> >> +					/*
> > >> >> >> +					 * Fail to find any suitable cpu.
> > >> >> >> +					 * The task will never come back!
> > >> >> >> +					 */
> > >> >> >> +					WARN_ON(1);
> > >> >> >
> > >> >> > Can this condition happen to users with a non-buggy kernel?

> I still haven't seen a satisfactory answer to this question. Please 
> don't resend patches without clearing questions raised during review.

So I had a look on Friday, it _should_ not happen, but it does due to a
second bug Juri is currently chasing down.