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Message-ID: <alpine.DEB.1.00.0803062111560.26462@chino.kir.corp.google.com>
Date: Thu, 6 Mar 2008 21:14:26 -0800 (PST)
From: David Rientjes <rientjes@...gle.com>
To: Balbir Singh <balbir@...ux.vnet.ibm.com>
cc: Paul Menage <menage@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>,
Pavel Emelianov <xemul@...nvz.org>,
Hugh Dickins <hugh@...itas.com>,
Sudhir Kumar <skumar@...ux.vnet.ibm.com>,
YAMAMOTO Takashi <yamamoto@...inux.co.jp>, lizf@...fujitsu.com,
linux-kernel@...r.kernel.org, taka@...inux.co.jp,
linux-mm@...ck.org,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
Subject: Re: [PATCH] Add cgroup support for enabling controllers at boot
time
On Fri, 7 Mar 2008, Balbir Singh wrote:
> >> +static int __init cgroup_disable(char *str)
> >> +{
> >> + int i;
> >> + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
> >> + struct cgroup_subsys *ss = subsys[i];
> >> + if (!strcmp(str, ss->name)) {
> >> + ss->disabled = 1;
> >> + break;
> >> + }
> >> + }
> >> +}
> >> +__setup("cgroup_disable=", cgroup_disable);
> >
> > This doesn't handle spaces very well, so isn't it possible for the name of
> > a current or future cgroup subsystem to be specified after cgroup_disable=
> > on the command line and have it disabled by accident?
> >
>
> How do you distinguish that from the user wanting to disable the controller on
> purpose? My understanding is that after parsing cgroup_disable=, the rest of the
> text is passed to cgroup_disable to process further. You'll find that all the
> __setup() code in the kernel is implemented this way.
>
Since the command line is logically delimited by spaces, you can
accidently disable a subsystem if its name appears in any of your kernel
options following your cgroup_disable= option. So if you're absolutely
confident that it wouldn't happen (for instance, if there's no logical
reason that a cgroup subsystem name should appear anywhere besides
cgroup_disable on the command line), then there's no objection.
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