linux-kernel - Re: [PATCH 08/16] freezer: use dedicated lock instead of task

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Message-ID: <20110828182124.GE27032@redhat.com>
Date:	Sun, 28 Aug 2011 20:21:24 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	rjw@...k.pl, paul@...lmenage.org, linux-kernel@...r.kernel.org,
	arnd@...db.de
Subject: Re: [PATCH 08/16] freezer: use dedicated lock instead of
	task_lock() + memory barrier

On 08/28, Oleg Nesterov wrote:
>
> Off-topic, but fake_signal_wake_up() is not safe if the caller
> try_to_freeze_cgroup(). Unlike try_to_freeze_tasks() (which holds
> tasklist) we can race with the exiting thread, ->sighand can be
> NULL.

Although with PF_NOFREEZE in do_exit() from 6/16, this race is only
theoretical.

And, forgot to mention, __thaw_task() looks racy too, but i think
this recalc_sigpending_and_wake() can simply go away.

Oleg.

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