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Date: Fri, 22 Oct 2010 14:57:08 -0700
From: Matt Helsley <matthltc@us.ibm.com>
To: Matt Helsley <matthltc@us.ibm.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>, containers@lists.linux-foundation.org,
        LKML <linux-kernel@vger.kernel.org>,
        Stephane Eranian <eranian@google.com>,
        "akpm >> Andrew Morton" <akpm@linux-foundation.org>,
        Paul Menage <menage@google.com>
Subject: Re: [PATCH 5/7] cgroups: Make freezer subsystem bindable
Message-ID: <20101022215708.GM10119@count0.beaverton.ibm.com>
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On Fri, Oct 22, 2010 at 01:57:55PM -0700, Matt Helsley wrote:
> On Fri, Oct 22, 2010 at 04:11:41PM +0800, Li Zefan wrote:
> > To make it bindable, we need to thaw all processes when unbinding
> > the freezer subsystem from a cgroup hierarchy.
> > 
> > Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>
> 
> Based on experience using cgroups and questions we've fielded in the
> past on IRC I'd say users will really appreciate this.
> 
> We're planning to use the freezer in checkpoint/restart. Since
> checkpoint requires the tasks to remain frozen for the duration of
> the syscall we add a kernel-internal freezer subsystem interface
> which prevents the cgroup from thawing. So we'll need some way to
> "block" unbinding for that as well.

And in case you're curious here are the portions of the checkpoint/restart
tree which implement the above:

http://www.linux-cr.org/git/?p=linux-cr.git;a=commitdiff;h=a584c1c6b729a544c76cbb173ce62ffb6575b1d3
http://www.linux-cr.org/git/?p=linux-cr.git;a=commitdiff;h=34869146ecd662352c0024e0769ec77e643fb1e1

Cheers,
	-Matt Helsley