netdev - [PATCH 0/2] (Was: pppd service crash in linux-3.13.6)

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Message-ID: <20140317180416.GA15708@redhat.com>
Date:	Mon, 17 Mar 2014 19:04:16 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Peter Hurley <peter@...leysoftware.com>,
	Andrew Morton <akpm@...ux-foundation.org>
Cc:	Sree Harsha Totakura <sreeharsha@...akura.in>,
	linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Jeff Dike <jdike@...toit.com>, Ingo Molnar <mingo@...e.hu>
Subject: [PATCH 0/2] (Was: pppd service crash in linux-3.13.6)

On 03/15, Peter Hurley wrote:
>
> On 03/14/2014 05:04 PM, Oleg Nesterov wrote:
>>
>> But it can't even know who called call_usermodehelper(). Besides,
>> cgroup_release_agent() uses UMH_WAIT_EXEC, so the caller can continue
>> and disappear completely before the usermode process has any chance
>> to do something.
>
> I'm just hypothesizing potential breakage, since the order of teardown
> is sensitive to changes, and I didn't do a complete audit of all the
> possibilities.

Yes, I understand your concerns. Still I do not see how cgroup_exit()
can depend on tty/namespace.

> If you feel strongly about moving disassociate_tty(), I won't object.

It is not that I feel really strongly... just in looks better to me.
If nothing else:

	1. If we actually can not do disassociate_ctty() before, say,
	   cgroup_exit(), then we should understand and document the
	   reason.

	2. task_work_add() can have more users in drivers/tty which
	   can be triggered by disassociate_tty() paths. So I think
	   it would be nice to call it before task_work_exit().

2/2 is offtopic and hopefully trivial.

Oleg.

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