linux-kernel - Re: [PATCH]: exec: avoid propagating PF_NO

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Message-ID: <20131128143411.GA10872@redhat.com>
Date:	Thu, 28 Nov 2013 15:34:11 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Tejun Heo <htejun@...il.com>, zhang.yi20@....com.cn,
	lkml <linux-kernel@...r.kernel.org>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>,
	Ingo Molnar <mingo@...hat.com>
Subject: Re: [PATCH]: exec: avoid propagating PF_NO_SETAFFINITY into
	userspace child

On 11/28, Peter Zijlstra wrote:
>
> On Thu, Nov 28, 2013 at 02:31:52PM +0100, Oleg Nesterov wrote:
> > I _guess_ usermodehelper_init() should use WQ_SYSFS then, and in this case
> > the user can write to wq_cpumask_store somewhere in /sys/.
>
> WTF is that and why are we creating alternative affinity interfaces when
> sched_setaffinity() is a prefectly fine one?

Because there is no a simple workqueue/thread connection, I guess.

And I do not understand why do you dislike this.

For example. Please note that with the new design we can even kill
khelper_wq and the ugly kmod_thread_locker hack (just in case, I am not
saying that the patch which added kmod_thread_locker was ugly ;).

We can just use one of the system_ WQ_UNBOUND workqueues which has
the "large enough" max_active.

Oleg.

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