From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: + cgroup_freezer-fix-can_attach-to-prohibit-moving-from-to-freezing-frozen-cgroups.patch added to -mm tree Date: Thu, 12 Aug 2010 12:32:32 -0700 Message-ID: <201008121932.o7CJWW90008583@imap1.linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from smtp1.linux-foundation.org ([140.211.169.13]:49628 "EHLO smtp1.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753158Ab0HLTco (ORCPT ); Thu, 12 Aug 2010 15:32:44 -0400 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: mm-commits@vger.kernel.org Cc: tomasz.buchert@inria.fr, lizf@cn.fujitsu.com, matthltc@us.ibm.com, menage@google.com The patch titled cgroup_freezer: fix can_attach() to prohibit moving from/to freezing/frozen cgroups has been added to the -mm tree. Its filename is cgroup_freezer-fix-can_attach-to-prohibit-moving-from-to-freezing-frozen-cgroups.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** See http://userweb.kernel.org/~akpm/stuff/added-to-mm.txt to find out what to do about this The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: cgroup_freezer: fix can_attach() to prohibit moving from/to freezing/frozen cgroups From: Tomasz Buchert It is possible to move a task from its cgroup even if this group is 'FREEZING'. This results in a nasty bug - the moved task will become frozen OUTSIDE its original cgroup and will remain in a permanent 'D' state. This patch allows to migrate the task only between THAWED cgroups. This behavior was observed and easily reproduced on a single core laptop. Notice that reproducibility depends highly on the machine used. Program and instructions how to reproduce the bug can be fetched from: http://pentium.hopto.org/~thinred/repos/linux-misc/freezer_bug.c Signed-off-by: Tomasz Buchert Cc: Matt Helsley Cc: Paul Menage Cc: Li Zefan Signed-off-by: Andrew Morton --- kernel/cgroup_freezer.c | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) diff -puN kernel/cgroup_freezer.c~cgroup_freezer-fix-can_attach-to-prohibit-moving-from-to-freezing-frozen-cgroups kernel/cgroup_freezer.c --- a/kernel/cgroup_freezer.c~cgroup_freezer-fix-can_attach-to-prohibit-moving-from-to-freezing-frozen-cgroups +++ a/kernel/cgroup_freezer.c @@ -173,24 +173,25 @@ static int freezer_can_attach(struct cgr /* * Anything frozen can't move or be moved to/from. - * - * Since orig_freezer->state == FROZEN means that @task has been - * frozen, so it's sufficient to check the latter condition. */ - if (is_task_frozen_enough(task)) + freezer = cgroup_freezer(new_cgroup); + if (freezer->state != CGROUP_THAWED) return -EBUSY; - freezer = cgroup_freezer(new_cgroup); - if (freezer->state == CGROUP_FROZEN) + rcu_read_lock(); + if (__cgroup_freezing_or_frozen(task)) { + rcu_read_unlock(); return -EBUSY; + } + rcu_read_unlock(); if (threadgroup) { struct task_struct *c; rcu_read_lock(); list_for_each_entry_rcu(c, &task->thread_group, thread_group) { - if (is_task_frozen_enough(c)) { + if (__cgroup_freezing_or_frozen(c)) { rcu_read_unlock(); return -EBUSY; } _ Patches currently in -mm which might be from tomasz.buchert@inria.fr are cgroup_freezer-unnecessary-test-in-cgroup_freezing_or_frozen.patch cgroup_freezer-fix-can_attach-to-prohibit-moving-from-to-freezing-frozen-cgroups.patch cgroup_freezer-update_freezer_state-does-incorrect-state-transitions.patch