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Date: Fri, 18 Sep 2009 23:15:34 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Wu Fei <at.wufei@gmail.com>, Ingo Molnar <mingo@elte.hu>,
       "Eric W. Biederman" <ebiederm@xmission.com>, arjan@infradead.org,
       jeremy@goop.org, mschmidt@redhat.com, mingo@redhat.com, hpa@zytor.com,
       linux-kernel@vger.kernel.org, tj@kernel.org, tglx@linutronix.de,
       Andrew Morton <akpm@linux-foundation.org>,
       linux-tip-commits@vger.kernel.org,
       Rusty Russell <rusty@rustcorp.com.au>
Subject: Re: [PATCH 0/1] kthreads: simplify !kthreadd_task logic, kill
	kthreadd_task_init_done
Message-ID: <20090918211534.GB19351@redhat.com>
References: <20090901135925.GA9083@elte.hu> <20090901145526.GA31317@redhat.com> <20090901165235.GA9105@redhat.com> <m13a76xnbw.fsf@fess.ebiederm.org> <20090902091340.GA5173@redhat.com> <20090904073749.GB20598@elte.hu> <20090918163241.GA8556@desktop> <20090918185425.GA16620@redhat.com> <alpine.LFD.2.01.0909181217270.4950@localhost.localdomain> <20090918211218.GA19351@redhat.com>
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On 09/18, Oleg Nesterov wrote:
>
> But personally I still can't understand what happens. If we were
> preempted somewhere before "kthreadd_task = find_task_by_pid_ns()"
> initialization, then schedule_debug() should complain? rest_init()
> runs under preempt_disable().

Ah. CONFIG_PREEMPT_VOLUNTARY means !CONFIG_PREEMPT, and Ingo mentioned
that SMP is disabled, this also means lock_kernel() is noop.

Oleg.