netdev - [PATCH 1/3] don't attach a task to a dead cgroup

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Message-Id: <1334875758-20939-2-git-send-email-glommer@parallels.com>
Date:	Thu, 19 Apr 2012 19:49:16 -0300
From:	Glauber Costa <glommer@...allels.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	<netdev@...r.kernel.org>, <cgroups@...r.kernel.org>,
	Li Zefan <lizefan@...wei.com>,
	<kamezawa.hiroyu@...fujitsu.com>,
	David Miller <davem@...emloft.net>, <devel@...nvz.org>,
	Glauber Costa <glommer@...allels.com>
Subject: [PATCH 1/3] don't attach a task to a dead cgroup

Not all external callers of cgroup_attach_task() test to
see if the cgroup is still live - the internal callers at
cgroup.c does.

With this test in cgroup_attach_task, we can assure that
no tasks are ever moved to a cgroup that is past its
destruction point and was already marked as dead.

Signed-off-by: Glauber Costa <glommer@...allels.com>
CC: Tejun Heo <tj@...nel.org>
CC: Li Zefan <lizefan@...wei.com>
CC: Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
---
 kernel/cgroup.c |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index b61b938..932c318 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -1927,6 +1927,9 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk)
 	struct cgroup_taskset tset = { };
 	struct css_set *newcg;
 
+	if (cgroup_is_removed(cgrp))
+		return -ENODEV;
+
 	/* @tsk either already exited or can't exit until the end */
 	if (tsk->flags & PF_EXITING)
 		return -ESRCH;
-- 
1.7.7.6

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