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Date: Sun, 28 Aug 2011 20:21:24 +0200
From: Oleg Nesterov <oleg@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: rjw@sisk.pl, paul@paulmenage.org, linux-kernel@vger.kernel.org,
        arnd@arndb.de
Subject: Re: [PATCH 08/16] freezer: use dedicated lock instead of
	task_lock() + memory barrier
Message-ID: <20110828182124.GE27032@redhat.com>
References: <1313763382-12341-1-git-send-email-tj@kernel.org> <1313763382-12341-9-git-send-email-tj@kernel.org> <20110828175116.GA27032@redhat.com>
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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.