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Date: Tue, 25 Oct 2016 18:17:25 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Roman Penyaev <roman.penyaev@profitbricks.com>
Cc: Andy Lutomirski <luto@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>,
        Tejun Heo <tj@kernel.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 1/1] kthread: allocate kthread structure using
        kmalloc
Message-ID: <20161025161725.GB13257@redhat.com>
References: <20161025110508.9052-1-roman.penyaev@profitbricks.com> <20161025140333.GB4326@redhat.com> <20161025154301.GA12015@redhat.com> <CAJrWOzArjn5-byFx1y9VLT9phnQBTQpWAhX96RVigRsF0h2pOQ@mail.gmail.com>
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Roman, I need to run away, just one note.

On 10/25, Roman Penyaev wrote:
>
> On Tue, Oct 25, 2016 at 5:43 PM, Oleg Nesterov <oleg@redhat.com> wrote:
>
> So in particular I do not understand this comment from the patch above
> where you abuse 'current->set_child_tid':
>
>  * This is the ugly but simple hack we will hopefully remove soon.
>
> how you are going to avoid this abuse of set_child_tid?

please ignore this comment. It actually reflects my desire to kill
struct kthread. If we won't do this, we can (ab)use this or another member
in task_struct.

> or vfork_done?
> because vfork_done is not only for waking up (yes, I totally agree, we
> can reuse task_work), it is also for getting a private data (like
> workqueue uses it):  task_struct->vfork_done->kthread->data.

kthreads simply should not use ->vfork_done at all. to_kthread() can
use the same pointer.

Oleg.