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

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Message-ID: <20131128150055.GA11956@redhat.com>
Date:	Thu, 28 Nov 2013 16:00:55 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <htejun@...il.com>
Cc:	Peter Zijlstra <peterz@...radead.org>, 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, Tejun Heo wrote:
>
> * Is WQ_RESCUER actually necessary?  If not, WQ_RESCUER will be
>   dropped and the task bearing the name of the workqueue will no
>   longer exist.

WQ_MEM_RECLAIM, I guess. Probably not...

> * Is ordered execution necessary?  If not, it can be converted to
>   alloc_workqueue() or just to use system_wq.

I think no. This is the reason for kmod_thread_locker hack.

> khelper is special as its attributes get inherited to its children,
> so, yeah, we probably wanna keep that one's cpumask set to all.

And btw. Note ____call_usermodehelper()->set_cpus_allowed_ptr(cpu_all_mask).

Even if we change the affinity of the "khelper" worker threads this
won't restrict the user-space helpers.

I think this set_cpus_allowed_ptr() should die in any case?

Oleg.

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