linux-kernel - Re: [PATCH 12/16] freezer: clean up freeze

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Date:	Mon, 29 Aug 2011 09:28:00 +0200
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	rjw@...k.pl, paul@...lmenage.org, linux-kernel@...r.kernel.org,
	arnd@...db.de
Subject: Re: [PATCH 12/16] freezer: clean up freeze_processes() failure path

Hello,

On Sun, Aug 28, 2011 at 08:09:01PM +0200, Oleg Nesterov wrote:
> This was copied from cancel_, yes. but what this
> recalc_sigpending_and_wake() can or should do?
>
> It looks simply pointless. It can't clear TIF_SIGPENDING,
> it can only do the unneeded/spurious wake_up(INTERRUPTIBLE).

Yeah, I just copied it over.  It seems it got confused between
recalc_sigpending() and recalc_sigpending_and_wake() where the latter
can't clear TIF_SIGPENDING.  The signallable freezable kthread seems
quite fragile.  Once TIF_SIGPENDING is set, the only way for it to be
cleared for a kthread is going through refrigerator and if freezing
gets canceled before that happens, the kthread will have stuck
TIF_SIGPENDING failing interruptible sleeps.  We'll probably should
move recalc_sigpending() to the top of refrigerator.

But that said, I don't see any in-kernel user of
set_freezable_with_signal().  Rafael, is there scheduled to be some
new user of this API?  It would be awesome if we can drop it.

Thanks.

-- 
tejun
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