From: Tejun Heo <htejun@gmail.com>
To: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
Cc: akpm@linux-foundation.org, mhocko@suse.cz,
kamezawa.hiroyu@jp.fujitsu.com, liwanp@linux.vnet.ibm.com,
lizefan@huawei.com, cgroups@vger.kernel.org, linux-mm@kvack.org
Subject: Re: [PATCH] cgroup: Don't drop the cgroup_mutex in cgroup_rmdir
Date: Fri, 20 Jul 2012 12:49:20 -0700 [thread overview]
Message-ID: <20120720194920.GB21218@google.com> (raw)
In-Reply-To: <1342706972-10912-1-git-send-email-aneesh.kumar@linux.vnet.ibm.com>
On Thu, Jul 19, 2012 at 07:39:32PM +0530, Aneesh Kumar K.V wrote:
> From: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
>
> 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 <aneesh.kumar@linux.vnet.ibm.com>
So, umm, let's not do this at this point. Please just fix memcg such
that it doesn't fail ->pre_destroy() and drop
subsys->__DEPRECATED_clear_css_refs. cgroup core won't give away new
references during or after pre_destroy that way and memcg is the ONLY
subsystem needing the deprecated behavior so it's rather
counter-productive to implement work-around at this point.
Nacked-And-Please-Drop-The-DEPRECATED-Behavior-by: Tejun Heo <tj@kernel.org>
Thanks.
--
tejun
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next prev parent reply other threads:[~2012-07-20 19:49 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20120718212637.133475C0050@hpza9.eem.corp.google.com>
2012-07-19 11:39 ` + hugetlb-cgroup-simplify-pre_destroy-callback.patch added to -mm tree Michal Hocko
2012-07-19 12:21 ` Aneesh Kumar K.V
2012-07-19 12:38 ` Michal Hocko
2012-07-19 13:48 ` Aneesh Kumar K.V
2012-07-19 14:09 ` [PATCH] cgroup: Don't drop the cgroup_mutex in cgroup_rmdir Aneesh Kumar K.V
2012-07-19 16:50 ` Tejun Heo
2012-07-20 15:45 ` Peter Zijlstra
2012-07-20 20:05 ` Tejun Heo
2012-07-20 22:07 ` Glauber Costa
2012-07-27 6:15 ` Li Zefan
2012-07-30 18:25 ` Tejun Heo
2012-07-20 7:51 ` Michal Hocko
2012-07-20 19:49 ` Tejun Heo [this message]
2012-07-20 1:05 ` + hugetlb-cgroup-simplify-pre_destroy-callback.patch added to -mm tree Kamezawa Hiroyuki
2012-07-20 1:20 ` Kamezawa Hiroyuki
2012-07-20 8:01 ` Michal Hocko
2012-07-20 8:08 ` Kamezawa Hiroyuki
2012-07-20 8:06 ` Michal Hocko
2012-07-20 19:18 ` Aneesh Kumar K.V
2012-07-20 19:56 ` Tejun Heo
2012-07-21 2:14 ` Kamezawa Hiroyuki
2012-07-21 2:46 ` Tejun Heo
2012-07-21 4:05 ` Kamezawa Hiroyuki
2012-07-22 17:34 ` Tejun Heo
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