From: Li Zefan <lizefan@huawei.com>
To: Tejun Heo <htejun@gmail.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>,
akpm@linux-foundation.org, mhocko@suse.cz,
kamezawa.hiroyu@jp.fujitsu.com, liwanp@linux.vnet.ibm.com,
cgroups@vger.kernel.org, linux-mm@kvack.org,
glommer@parallels.com
Subject: Re: [PATCH] cgroup: Don't drop the cgroup_mutex in cgroup_rmdir
Date: Fri, 27 Jul 2012 14:15:12 +0800 [thread overview]
Message-ID: <501231F0.8050505@huawei.com> (raw)
In-Reply-To: <20120720200542.GD21218@google.com>
On 2012/7/21 4:05, Tejun Heo wrote:
> Hey, Peter.
>
> On Fri, Jul 20, 2012 at 05:45:40PM +0200, Peter Zijlstra wrote:
>>> So, Peter, why does cpuset mangle with cgroup_mutex? What guarantees
>>> does it need? Why can't it work on "changed" notification while
>>> caching the current css like blkcg does?
>>
>> I've no clue sorry.. /me goes stare at this stuff.. Looks like something
>> Paul Menage did when he created cgroups. I'll have to have a hard look
>> at all that to untangle this. Not something obvious to me.
>
> Yeah, it would be great if this can be untangled. I really don't see
> any other reasonable way out of this circular locking mess. If cpuset
> needs stable css association across certain period, the RTTD is
> caching the css by holding its ref and synchronize modifications to
> that cache, rather than synchronizing cgroup operations themselves.
>
The cgroup core was extracted from cpuset, so they are deeply tangled.
There are several issues to resolve with regard to removing cgroup lock from cpuset.
- there are places that the cgroup hierarchy is travelled. This should be
easy, as cpuset can be made to maintain its hierarchy.
- cpuset disallows clearing cpuset.mems/cpuset.cpus if the cgroup is not empty,
which can be guaranteed only by cgroup lock.
- cpuset disallows a task be attached to a cgroup with empty cpuset.mems/cpuset.cpus,
which again can be guarantted only by cgroup lock.
- cpuset may move tasks from a cgroup to another cgroup (Glauber mentioned this).
- maybe other cases I overlooked..
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next prev parent reply other threads:[~2012-07-27 6:18 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 [this message]
2012-07-30 18:25 ` Tejun Heo
2012-07-20 7:51 ` Michal Hocko
2012-07-20 19:49 ` Tejun Heo
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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