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Date: Sun, 30 Oct 2011 18:18:46 +0100
From: Lennart Poettering <mzxreary@0pointer.de>
To: Li Zefan <lizf@cn.fujitsu.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>,
        Paul Menage <paul@paulmenage.org>, Kay Sievers <kay.sievers@vrfy.org>,
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Subject: Re: A =?utf-8?Q?Plumber=E2=80=99?=
	=?utf-8?Q?s?= Wish List for Linux
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On Tue, 25.10.11 13:40, Li Zefan (lizf@cn.fujitsu.com) wrote:

> > cgroups provides us with all of that, though the last two items only in
> > a suboptimal way: notification of cgroups running empty is ugly, since
> > it is done by spawning a usermode helper (we'd prefer a netlink msg or
> > so), and the process killing is a bit racy.
> 
> How about using eventfd? You can create an eventfd for the specific "tasks"
> file, and when the cgroup gets empty (no task in it), you'll get a notification.
> 
> It should be easy to implement, since cgroup already supports eventfd-based
> API.

I am quite convinced that using eventfd() like this is quite ugly. The
current evetnfd() logic is not recursive anyway, hence wouldn't help us
much.

Lennart

-- 
Lennart Poettering - Red Hat, Inc.