From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751858AbcFVWqf (ORCPT ); Wed, 22 Jun 2016 18:46:35 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:46313 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752452AbcFVWmA (ORCPT ); Wed, 22 Jun 2016 18:42:00 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Tejun Heo , Vladimir Davydov , Johannes Weiner , Michal Hocko , Andrew Morton , Linus Torvalds Subject: [PATCH 4.4 44/75] memcg: add RCU locking around css_for_each_descendant_pre() in memcg_offline_kmem() Date: Wed, 22 Jun 2016 15:41:06 -0700 Message-Id: <20160622223502.242549598@linuxfoundation.org> X-Mailer: git-send-email 2.9.0 In-Reply-To: <20160622223500.055133765@linuxfoundation.org> References: <20160622223500.055133765@linuxfoundation.org> User-Agent: quilt/0.64 MIME-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-15 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 4.4-stable review patch. If anyone has any objections, please let me know. ------------------ From: Tejun Heo commit 3a06bb78ceeceacc86a1e31133a7944013f9775b upstream. memcg_offline_kmem() may be called from memcg_free_kmem() after a css init failure. memcg_free_kmem() is a ->css_free callback which is called without cgroup_mutex and memcg_offline_kmem() ends up using css_for_each_descendant_pre() without any locking. Fix it by adding rcu read locking around it. mkdir: cannot create directory `65530': No space left on device =============================== [ INFO: suspicious RCU usage. ] 4.6.0-work+ #321 Not tainted ------------------------------- kernel/cgroup.c:4008 cgroup_mutex or RCU read lock required! [ 527.243970] other info that might help us debug this: [ 527.244715] rcu_scheduler_active = 1, debug_locks = 0 2 locks held by kworker/0:5/1664: #0: ("cgroup_destroy"){.+.+..}, at: [] process_one_work+0x165/0x4a0 #1: ((&css->destroy_work)#3){+.+...}, at: [] process_one_work+0x165/0x4a0 [ 527.248098] stack backtrace: CPU: 0 PID: 1664 Comm: kworker/0:5 Not tainted 4.6.0-work+ #321 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.9.1-1.fc24 04/01/2014 Workqueue: cgroup_destroy css_free_work_fn Call Trace: dump_stack+0x68/0xa1 lockdep_rcu_suspicious+0xd7/0x110 css_next_descendant_pre+0x7d/0xb0 memcg_offline_kmem.part.44+0x4a/0xc0 mem_cgroup_css_free+0x1ec/0x200 css_free_work_fn+0x49/0x5e0 process_one_work+0x1c5/0x4a0 worker_thread+0x49/0x490 kthread+0xea/0x100 ret_from_fork+0x1f/0x40 Link: http://lkml.kernel.org/r/20160526203018.GG23194@mtj.duckdns.org Signed-off-by: Tejun Heo Acked-by: Vladimir Davydov Acked-by: Johannes Weiner Cc: Michal Hocko Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds Signed-off-by: Greg Kroah-Hartman --- mm/memcontrol.c | 3 +++ 1 file changed, 3 insertions(+) --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -3661,6 +3661,7 @@ static void memcg_deactivate_kmem(struct * ordering is imposed by list_lru_node->lock taken by * memcg_drain_all_list_lrus(). */ + rcu_read_lock(); /* can be called from css_free w/o cgroup_mutex */ css_for_each_descendant_pre(css, &memcg->css) { child = mem_cgroup_from_css(css); BUG_ON(child->kmemcg_id != kmemcg_id); @@ -3668,6 +3669,8 @@ static void memcg_deactivate_kmem(struct if (!memcg->use_hierarchy) break; } + rcu_read_unlock(); + memcg_drain_all_list_lrus(kmemcg_id, parent->kmemcg_id); memcg_free_cache_id(kmemcg_id);