From: Kamezawa Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
To: Tejun Heo <tj@kernel.org>
Cc: lizefan@huawei.com, hannes@cmpxchg.org, mhocko@suse.cz,
bsingharora@gmail.com, containers@lists.linux-foundation.org,
cgroups@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 4/8] cgroup: deactivate CSS's and mark cgroup dead before invoking ->pre_destroy()
Date: Fri, 02 Nov 2012 18:43:47 +0900 [thread overview]
Message-ID: <509395D3.2070708@jp.fujitsu.com> (raw)
In-Reply-To: <1351657365-25055-5-git-send-email-tj@kernel.org>
(2012/10/31 13:22), Tejun Heo wrote:
> Because ->pre_destroy() could fail and can't be called under
> cgroup_mutex, cgroup destruction did something very ugly.
>
> 1. Grab cgroup_mutex and verify it can be destroyed; fail otherwise.
>
> 2. Release cgroup_mutex and call ->pre_destroy().
>
> 3. Re-grab cgroup_mutex and verify it can still be destroyed; fail
> otherwise.
>
> 4. Continue destroying.
>
> In addition to being ugly, it has been always broken in various ways.
> For example, memcg ->pre_destroy() expects the cgroup to be inactive
> after it's done but tasks can be attached and detached between #2 and
> #3 and the conditions that memcg verified in ->pre_destroy() might no
> longer hold by the time control reaches #3.
>
> Now that ->pre_destroy() is no longer allowed to fail. We can switch
> to the following.
>
> 1. Grab cgroup_mutex and fail if it can't be destroyed; fail
> otherwise.
>
> 2. Deactivate CSS's and mark the cgroup removed thus preventing any
> further operations which can invalidate the verification from #1.
>
> 3. Release cgroup_mutex and call ->pre_destroy().
>
> 4. Re-grab cgroup_mutex and continue destroying.
>
> After this change, controllers can safely assume that ->pre_destroy()
> will only be called only once for a given cgroup and, once
> ->pre_destroy() is called, the cgroup will stay dormant till it's
> destroyed.
>
> Signed-off-by: Tejun Heo <tj@kernel.org>
Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
Ok, cgroup_lock_live_group() will work synchronously against attach_task().
I welcome this.
next prev parent reply other threads:[~2012-11-02 9:44 UTC|newest]
Thread overview: 61+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-31 4:22 [PATCHSET] cgroup: simplify cgroup removal path Tejun Heo
2012-10-31 4:22 ` [PATCH 1/8] cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs Tejun Heo
2012-10-31 13:21 ` Glauber Costa
2012-10-31 16:38 ` Tejun Heo
2012-10-31 14:37 ` Michal Hocko
2012-10-31 16:41 ` Tejun Heo
2012-10-31 16:48 ` Michal Hocko
2012-10-31 17:22 ` Tejun Heo
2012-11-02 9:23 ` Kamezawa Hiroyuki
2012-10-31 4:22 ` [PATCH 2/8] cgroup: kill CSS_REMOVED Tejun Heo
2012-10-31 15:39 ` Michal Hocko
2012-10-31 16:57 ` Tejun Heo
2012-10-31 17:06 ` Glauber Costa
2012-10-31 17:10 ` Tejun Heo
2012-10-31 17:19 ` Glauber Costa
2012-10-31 17:25 ` Tejun Heo
2012-10-31 17:38 ` Glauber Costa
2012-10-31 17:44 ` Tejun Heo
2012-10-31 17:39 ` Glauber Costa
2012-10-31 19:16 ` Michal Hocko
2012-10-31 19:33 ` Tejun Heo
2012-11-02 9:30 ` Kamezawa Hiroyuki
2012-10-31 4:22 ` [PATCH 3/8] cgroup: use cgroup_lock_live_group(parent) in cgroup_create() Tejun Heo
2012-10-31 15:55 ` Michal Hocko
2012-10-31 17:04 ` Tejun Heo
2012-11-01 9:16 ` Michal Hocko
2012-11-01 14:52 ` Tejun Heo
2012-11-01 15:05 ` Michal Hocko
2012-11-01 15:15 ` Michal Hocko
2012-11-01 15:43 ` Tejun Heo
2012-11-02 9:37 ` Kamezawa Hiroyuki
2012-10-31 4:22 ` [PATCH 4/8] cgroup: deactivate CSS's and mark cgroup dead before invoking ->pre_destroy() Tejun Heo
2012-10-31 13:42 ` Glauber Costa
2012-10-31 16:05 ` Michal Hocko
2012-11-02 9:43 ` Kamezawa Hiroyuki [this message]
2012-10-31 4:22 ` [PATCH 5/8] cgroup: remove CGRP_WAIT_ON_RMDIR, cgroup_exclude_rmdir() and cgroup_release_and_wakeup_rmdir() Tejun Heo
2012-10-31 16:27 ` Michal Hocko
2012-10-31 17:16 ` Tejun Heo
2012-11-02 9:53 ` Kamezawa Hiroyuki
2012-10-31 4:22 ` [PATCH 6/8] memcg: make mem_cgroup_reparent_charges non failing Tejun Heo
2012-11-02 9:54 ` Kamezawa Hiroyuki
2012-10-31 4:22 ` [PATCH 7/8] hugetlb: do not fail in hugetlb_cgroup_pre_destroy Tejun Heo
2012-11-02 9:56 ` Kamezawa Hiroyuki
2012-10-31 4:22 ` [PATCH 8/8] cgroup: make ->pre_destroy() return void Tejun Heo
2012-10-31 13:57 ` Vivek Goyal
2012-10-31 16:28 ` Michal Hocko
2012-11-02 9:57 ` Kamezawa Hiroyuki
2012-10-31 13:49 ` [PATCHSET] cgroup: simplify cgroup removal path Glauber Costa
2012-10-31 17:18 ` Tejun Heo
2012-10-31 17:24 ` Glauber Costa
2012-10-31 17:26 ` Tejun Heo
2012-10-31 17:33 ` Glauber Costa
2012-10-31 16:31 ` Michal Hocko
2012-10-31 16:35 ` Tejun Heo
-- strict thread matches above, loose matches on Subject: below --
2012-10-31 18:16 [PATCHSET v2] " Tejun Heo
2012-10-31 18:16 ` [PATCH 4/8] cgroup: deactivate CSS's and mark cgroup dead before invoking ->pre_destroy() Tejun Heo
2012-10-31 19:44 [PATCHSET RESEND v2] cgroup: simplify cgroup removal path Tejun Heo
2012-10-31 19:44 ` [PATCH 4/8] cgroup: deactivate CSS's and mark cgroup dead before invoking ->pre_destroy() Tejun Heo
2012-10-31 21:23 ` Michal Hocko
2012-10-31 21:27 ` Tejun Heo
2012-11-01 8:58 ` Michal Hocko
2012-11-02 10:05 ` Kamezawa Hiroyuki
2012-11-05 5:37 ` Li Zefan
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