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Date:   Wed, 6 Jun 2018 17:22:45 +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,
        linux-kernel@vger.kernel.org, linux-arm-msm@vger.kernel.org,
        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:
> On 06/05, Peter Zijlstra wrote:
> >
> > Also, I think we still need TASK_PARKED as a special state for that.
> 
> I think it would be nice to kill the TASK_PARKED state altogether. But I don't
> know how. I'll try to look at this code later, but I am not sure I will find a
> way to cleanup it...

So the nice thing about having TASK_PARKED is that it guarantees no
spurious wakeups. You know the thread will not wake up while it's CPU is
gone.

We could possibly re-purpose TASK_STOPPED (because kernel threads don't
do that) but that seems dodgy at best.