linux-kernel - Re: [PATCH] apm-emulation: use wait_event_freezable() instead of freezer_[do_not

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Message-ID: <20110818173511.GB6910@redhat.com>
Date:	Thu, 18 Aug 2011 19:35:11 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	Jiri Kosina <jkosina@...e.cz>, linux-kernel@...r.kernel.org,
	Russell King <linux@....linux.org.uk>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Paul Mundt <lethal@...ux-sh.org>
Subject: Re: [PATCH] apm-emulation: use wait_event_freezable() instead of
	freezer_[do_not_]count()

Hi Tejun,

The patch looks fine even if I know nothing about this code.

But I have a bit off-topic question,

On 08/18, Tejun Heo wrote:
>
> vfork is moving away from freezer_[do_not_]count() one way or the
> other

Yes, I think we should do this in any case.

> Use wait_event_freezable() instead.
>
> The only annoyance is that wait_event_freezable() wakes up with
> -ERESTART if there are pending signals

IOW, we do not have wait_event_freezable_uninterruptible/etc.

Perhaps we can introduce TASK_FREEZABLE ? It should be used along
with TASK_UNINTERRUPTIBLE (like TASK_WAKEKILL). freeze_task() can
use TASK_INTERRUPTIBLE | FREEZABLE for wake_up.

vfork() can use FREEZABLE too (although this is not needed in the
long term, we should teach it to sleep in TASK_INTERRUPTIBLE).

But I feel you are going to reimplement freezer completely, in this
case please ignore.

Oleg.

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