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Date: Wed, 9 Nov 2016 08:58:36 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Oleg Nesterov <oleg@redhat.com>
cc: Andy Lutomirski <luto@amacapital.net>,
        Roman Pen <roman.penyaev@profitbricks.com>,
        Andy Lutomirski <luto@kernel.org>,
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        Chunming Zhou <David1.Zhou@amd.com>,
        Alex Deucher <alexander.deucher@amd.com>
Subject: Re: [PATCH 1/2] kthread: don't use to_live_kthread() in
 kthread_stop()
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On Mon, 31 Oct 2016, Oleg Nesterov wrote:

> kthread_stop() had to use to_live_kthread() simply because it was not
> possible to access kthread->exited after the exiting kthread clears
> task_struct->vfork_done. Now that to_kthread() is always valid we can
> do wake_up_process() + wait_for_completion() unconditionally, we don't
> care if it has already passed complete_vfork_done() or even dead.
> 
> The exiting kthread can get the spurious wakeup after mm_release() but
> this is possible without this change too and this is fine, do_task_dead()
> ensures that this can't make any harm.
> 
> Note: we can even change this function to use task_work_add() and avoid
> ->vfork_done altogether, probably we will do this later.
> 
> Signed-off-by: Oleg Nesterov <oleg@redhat.com>

Reviewed-by: Thomas Gleixner <tglx@linutronix.de>