From: Ben Blum <bblum@andrew.cmu.edu>
Date: Wed, 2 Nov 2011 20:38:07 +0000 (-0700)
Subject: cgroups: don't attach task to subsystem if migration failed
X-Git-Tag: v3.2-rc1~82^2~39
X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=77ceab8ea590d7dc6c8f055ce43dfebd74428107;p=pandora-kernel.git

cgroups: don't attach task to subsystem if migration failed

If a task has exited to the point it has called cgroup_exit() already,
then we can't migrate it to another cgroup anymore.

This can happen when we are attaching a task to a new cgroup between the
call to ->can_attach_task() on subsystems and the migration that is
eventually tried in cgroup_task_migrate().

In this case cgroup_task_migrate() returns -ESRCH and we don't want to
attach the task to the subsystems because the attachment to the new cgroup
itself failed.

Fix this by only calling ->attach_task() on the subsystems if the cgroup
migration succeeded.

Reported-by: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Ben Blum <bblum@andrew.cmu.edu>
Acked-by: Paul Menage <paul@paulmenage.org>
Cc: Li Zefan <lizf@cn.fujitsu.com>
Cc: Tejun Heo <tj@kernel.org>
Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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