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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20131128133947.GR10022@twins.programming.kicks-ass.net>
Date:	Thu, 28 Nov 2013 14:39:47 +0100
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
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 Thu, Nov 28, 2013 at 02:31:52PM +0100, Oleg Nesterov wrote:
> On 11/28, Peter Zijlstra wrote:
> >
> > On Thu, Nov 28, 2013 at 12:45:42PM +0100, Oleg Nesterov wrote:
> > > It has? khelper is a workqueue thread, this flag is set by create_worker().
> > >
> > > And it does kernel_thread() (not kthread_create()) so the child gets this
> > > flag too.
> >
> > Urgh, but that's still completely wrong. khelper is a singlethread
> > workqueue, those should be unbound and therefore should not have this
> > flag set at all.
> 
> Well. This is debatable, but I leave this to you and Tejun ;)

How can that be debatable? I don't see a single argument in favour of
doing that; its plain ridiculous.

> > In fact, I know people want to set affinity on khelper
> 
> This is not that simple. Note that khelper itself is the rescuer thread,
> it doesn't not process the works. There are other kworker/u* threads which
> run the work queued on khelper_wq. There is a pool of threads.

That's just fucked. WTF does singlethreaded mean then?

A single parent process for all usermode helpers makes so much sense;
not doing it is just weird.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/