linux-kernel - Re: [PATCH v3 1/1] kthread: allocate kthread structure using kmalloc

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Message-ID: <20161025154301.GA12015@redhat.com>
Date:   Tue, 25 Oct 2016 17:43:02 +0200
From:   Oleg Nesterov <oleg@...hat.com>
To:     Roman Pen <roman.penyaev@...fitbricks.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, Tejun Heo <tj@...nel.org>,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] kthread: allocate kthread structure using
        kmalloc

On 10/25, Oleg Nesterov wrote:
>
> On 10/25, Roman Pen wrote:
> >
> > This patch avoids allocation of kthread structure on a stack, and simply
> > uses kmalloc.
>
> Oh. I didn't even read this patch, but I have to admit I personally do not
> like it. I can be wrong, but imo this is the step to the wrong direction.

And after I tried to actually read it I dislike it even more, sorry Roman.
Starting from the fact it moves kthread_create_info into struct kthread.

> struct kthread is already bloated, we should not bloat it more. Instead
> we should kill it. And to_kthread() too, at least in its current form.

Yes, but even if we can't or do not want to do this, even if we want to
kmalloc struct kthread, I really think it should not be refcounted
separately from task_struct.

something like the patch in http://marc.info/?l=linux-kernel&m=146715459127804

Either way to_live_kthread() must go away. Currently we can't avoid it
because we abuse vfork_done, but as I already said we no longer need this.

Oleg.