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Date: Wed, 6 Jun 2018 17:03:10 +0200
From: Peter Zijlstra <peterz@infradead.org>
To: Oleg Nesterov <oleg@redhat.com>
Cc: "Kohli, Gaurav" <gkohli@codeaurora.org>, tglx@linutronix.de,
        mpe@ellerman.id.au, mingo@kernel.org, bigeasy@linutronix.de,
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        Neeraj Upadhyay <neeraju@codeaurora.org>,
        Will Deacon <will.deacon@arm.com>
Subject: Re: [PATCH v1] kthread/smpboot: Serialize kthread parking against
 wakeup
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On Wed, Jun 06, 2018 at 03:51:16PM +0200, Oleg Nesterov wrote:
> In particular, I think that kthread_park() on a parked kthread
> must not be possible.

It happens though; I put in a WARN and someone triggered it -- although
I could not reproduce :/