From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx163.postini.com [74.125.245.163]) by kanga.kvack.org (Postfix) with SMTP id 944F46B0044 for ; Thu, 19 Jul 2012 10:09:58 -0400 (EDT) Received: from /spool/local by e28smtp05.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Thu, 19 Jul 2012 19:39:55 +0530 Received: from d28av05.in.ibm.com (d28av05.in.ibm.com [9.184.220.67]) by d28relay05.in.ibm.com (8.13.8/8.13.8/NCO v10.0) with ESMTP id q6JE9qTV65994762 for ; Thu, 19 Jul 2012 19:39:52 +0530 Received: from d28av05.in.ibm.com (loopback [127.0.0.1]) by d28av05.in.ibm.com (8.14.4/8.13.1/NCO v10.0 AVout) with ESMTP id q6JJeNFi013710 for ; Fri, 20 Jul 2012 05:40:27 +1000 From: "Aneesh Kumar K.V" Subject: [PATCH] cgroup: Don't drop the cgroup_mutex in cgroup_rmdir Date: Thu, 19 Jul 2012 19:39:32 +0530 Message-Id: <1342706972-10912-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com> In-Reply-To: <87ipdjc15j.fsf@skywalker.in.ibm.com> References: <87ipdjc15j.fsf@skywalker.in.ibm.com> Sender: owner-linux-mm@kvack.org List-ID: To: akpm@linux-foundation.org, mhocko@suse.cz, kamezawa.hiroyu@jp.fujitsu.com, liwanp@linux.vnet.ibm.com, htejun@gmail.com, lizefan@huawei.com, cgroups@vger.kernel.org, linux-mm@kvack.org Cc: "Aneesh Kumar K.V" From: "Aneesh Kumar K.V" We dropped cgroup mutex, because of a deadlock between memcg and cpuset. cpuset took hotplug lock followed by cgroup_mutex, where as memcg pre_destroy did lru_add_drain_all() which took hotplug lock while already holding cgroup_mutex. The deadlock is explained in 3fa59dfbc3b223f02c26593be69ce6fc9a940405 But dropping cgroup_mutex in cgroup_rmdir also means tasks could get added to cgroup while we are in pre_destroy. This makes error handling in pre_destroy complex. So move the unlock/lock to memcg pre_destroy callback. Core cgroup will now call pre_destroy with cgroup_mutex held. Signed-off-by: Aneesh Kumar K.V --- kernel/cgroup.c | 3 +-- mm/memcontrol.c | 11 ++++++++++- 2 files changed, 11 insertions(+), 3 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 7981850..01c67f4 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -4151,7 +4151,6 @@ again: mutex_unlock(&cgroup_mutex); return -EBUSY; } - mutex_unlock(&cgroup_mutex); /* * In general, subsystem has no css->refcnt after pre_destroy(). But @@ -4171,10 +4170,10 @@ again: ret = cgroup_call_pre_destroy(cgrp); if (ret) { clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags); + mutex_unlock(&cgroup_mutex); return ret; } - mutex_lock(&cgroup_mutex); parent = cgrp->parent; if (atomic_read(&cgrp->count) || !list_empty(&cgrp->children)) { clear_bit(CGRP_WAIT_ON_RMDIR, &cgrp->flags); diff --git a/mm/memcontrol.c b/mm/memcontrol.c index e8ddc00..9bd56ee 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -4993,9 +4993,18 @@ free_out: static int mem_cgroup_pre_destroy(struct cgroup *cont) { + int ret; struct mem_cgroup *memcg = mem_cgroup_from_cont(cont); - return mem_cgroup_force_empty(memcg, false); + cgroup_unlock(); + /* + * we call lru_add_drain_all, which end up taking + * mutex_lock(&cpu_hotplug.lock), But cpuset have + * the reverse order. So drop the cgroup lock + */ + ret = mem_cgroup_force_empty(memcg, false); + cgroup_lock(); + return ret; } static void mem_cgroup_destroy(struct cgroup *cont) -- 1.7.10 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org