Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755219AbYKFBVl (ORCPT ); Wed, 5 Nov 2008 20:21:41 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753116AbYKFBVd (ORCPT ); Wed, 5 Nov 2008 20:21:33 -0500 Received: from cn.fujitsu.com ([222.73.24.84]:53752 "EHLO song.cn.fujitsu.com" rhost-flags-OK-FAIL-OK-OK) by vger.kernel.org with ESMTP id S1753095AbYKFBVc (ORCPT ); Wed, 5 Nov 2008 20:21:32 -0500 Message-ID: <491245F1.5070707@cn.fujitsu.com> Date: Thu, 06 Nov 2008 09:18:41 +0800 From: Li Zefan User-Agent: Thunderbird 2.0.0.9 (X11/20071115) MIME-Version: 1.0 To: Andrew Morton CC: Matt Helsley , Cedric Le Goater , "Serge E. Hallyn" , Paul Menage , LKML , Linux Containers Subject: [PATCH -v2] freezer_cg: disable writing freezer.state of root cgroup Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2575 Lines: 78 With this change, control file 'freezer.state' doesn't exist in root cgroup, making root cgroup unfreezable. I think it's reasonable to disallow freeze tasks in the root cgroup. And then we can avoid fork overhead when freezer subsystem is compiled but not used. Also make writing invalid value to freezer.state returns EINVAL rather than EIO. This is more consistent with other cgroup subsystem. Signed-off-by: Li Zefan --- patch is based on freezer_cg-remove-task_lock-from-freezer_fork.patch --- Documentation/cgroups/freezer-subsystem.txt | 3 +++ kernel/cgroup_freezer.c | 11 ++++++++++- 2 files changed, 13 insertions(+), 1 deletions(-) diff --git a/Documentation/cgroups/freezer-subsystem.txt b/Documentation/cgroups/freezer-subsystem.txt index c50ab58..91572b9 100644 --- a/Documentation/cgroups/freezer-subsystem.txt +++ b/Documentation/cgroups/freezer-subsystem.txt @@ -54,6 +54,9 @@ freezer.state. Writing "FROZEN" to the state file will freeze all tasks in the cgroup. Subsequently writing "THAWED" will unfreeze the tasks in the cgroup. Reading will return the current state. +Note freezer.state doesn't exist in root cgroup, which means root cgroup +is unfreezable. + * Examples of usage : # mkdir /containers/freezer diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c index 6605907..cf3fce9 100644 --- a/kernel/cgroup_freezer.c +++ b/kernel/cgroup_freezer.c @@ -192,6 +192,13 @@ static void freezer_fork(struct cgroup_subsys *ss, struct task_struct *task) */ freezer = task_freezer(task); + /* + * The root cgroup is unfreezable, so we can skip the + * following check. + */ + if (!freezer->css.cgroup->parent) + return; + spin_lock_irq(&freezer->lock); BUG_ON(freezer->state == CGROUP_FROZEN); @@ -335,7 +342,7 @@ static int freezer_write(struct cgroup *cgroup, else if (strcmp(buffer, freezer_state_strs[CGROUP_FROZEN]) == 0) goal_state = CGROUP_FROZEN; else - return -EIO; + return -EINVAL; if (!cgroup_lock_live_group(cgroup)) return -ENODEV; @@ -354,6 +361,8 @@ static struct cftype files[] = { static int freezer_populate(struct cgroup_subsys *ss, struct cgroup *cgroup) { + if (!cgroup->parent) + return 0; return cgroup_add_files(cgroup, ss, files, ARRAY_SIZE(files)); } -- 1.5.4.rc3 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/