From: Michal Hocko <mhocko-AlSwsSmVLrQ@public.gmane.org>
To: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org,
cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
Subject: Re: [PATCH 1/8] cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs
Date: Wed, 31 Oct 2012 21:08:59 +0100 [thread overview]
Message-ID: <20121031200859.GE1271@dhcp22.suse.cz> (raw)
In-Reply-To: <1351712650-23709-2-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
On Wed 31-10-12 12:44:03, Tejun Heo wrote:
[...]
> local_irq_save/restore() from cgroup_clear_css_refs() are replaced
> with local_irq_disable/enable() for simplicity. This is safe as
> cgroup_rmdir() is always called with IRQ enabled. Note that this IRQ
> switching is necessary to make CSS deactivation and CSS_REMOVED
> assertion atomic against css_tryget() and will be removed by future
> changes.
local_irq_disable doesn't guarantee atomicity, because other CPUs will
see the change in steps so this is a bit misleading. The real reason
AFAICS is that we do not want to hang in css_tryget from IRQ context
(does this really happen btw.?) which would interrupt cgroup_rmdir
between we add CSS_DEACT_BIAS and the group is marked CGRP_REMOVED.
Or am I still missing the point?
[...]
--
Michal Hocko
SUSE Labs
WARNING: multiple messages have this Message-ID (diff)
From: Michal Hocko <mhocko@suse.cz>
To: Tejun Heo <tj@kernel.org>
Cc: lizefan@huawei.com, hannes@cmpxchg.org, bsingharora@gmail.com,
kamezawa.hiroyu@jp.fujitsu.com,
containers@lists.linux-foundation.org, cgroups@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/8] cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs
Date: Wed, 31 Oct 2012 21:08:59 +0100 [thread overview]
Message-ID: <20121031200859.GE1271@dhcp22.suse.cz> (raw)
In-Reply-To: <1351712650-23709-2-git-send-email-tj@kernel.org>
On Wed 31-10-12 12:44:03, Tejun Heo wrote:
[...]
> local_irq_save/restore() from cgroup_clear_css_refs() are replaced
> with local_irq_disable/enable() for simplicity. This is safe as
> cgroup_rmdir() is always called with IRQ enabled. Note that this IRQ
> switching is necessary to make CSS deactivation and CSS_REMOVED
> assertion atomic against css_tryget() and will be removed by future
> changes.
local_irq_disable doesn't guarantee atomicity, because other CPUs will
see the change in steps so this is a bit misleading. The real reason
AFAICS is that we do not want to hang in css_tryget from IRQ context
(does this really happen btw.?) which would interrupt cgroup_rmdir
between we add CSS_DEACT_BIAS and the group is marked CGRP_REMOVED.
Or am I still missing the point?
[...]
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2012-10-31 20:08 UTC|newest]
Thread overview: 110+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-31 19:44 [PATCHSET RESEND v2] cgroup: simplify cgroup removal path Tejun Heo
2012-10-31 19:44 ` Tejun Heo
2012-10-31 19:44 ` [PATCH 4/8] cgroup: deactivate CSS's and mark cgroup dead before invoking ->pre_destroy() Tejun Heo
[not found] ` <1351712650-23709-5-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-10-31 21:23 ` Michal Hocko
2012-10-31 21:23 ` Michal Hocko
[not found] ` <20121031212359.GC5286-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2012-10-31 21:27 ` Tejun Heo
2012-10-31 21:27 ` Tejun Heo
[not found] ` <20121031212725.GA2945-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2012-11-01 8:58 ` Michal Hocko
2012-11-01 8:58 ` Michal Hocko
2012-11-02 10:05 ` Kamezawa Hiroyuki
2012-11-02 10:05 ` Kamezawa Hiroyuki
2012-11-05 5:37 ` Li Zefan
2012-11-05 5:37 ` Li Zefan
2012-10-31 19:44 ` [PATCH 8/8] cgroup: make ->pre_destroy() return void Tejun Heo
[not found] ` <1351712650-23709-9-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-10-31 21:23 ` Michal Hocko
2012-10-31 21:23 ` Michal Hocko
2012-11-02 10:24 ` Kamezawa Hiroyuki
2012-11-02 10:24 ` Kamezawa Hiroyuki
2012-11-02 10:24 ` Kamezawa Hiroyuki
2012-11-05 5:41 ` Li Zefan
2012-11-05 5:41 ` Li Zefan
[not found] ` <1351712650-23709-1-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-10-31 19:44 ` [PATCH 1/8] cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs Tejun Heo
2012-10-31 19:44 ` Tejun Heo
[not found] ` <1351712650-23709-2-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-10-31 20:08 ` Michal Hocko [this message]
2012-10-31 20:08 ` Michal Hocko
[not found] ` <20121031200859.GE1271-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2012-10-31 20:11 ` Tejun Heo
2012-10-31 20:11 ` Tejun Heo
[not found] ` <CAOS58YPbYoMJ1+3uRfK_ZERyZoaby=FPW7uTpp8dVOSgYC8Mrw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-10-31 20:14 ` Michal Hocko
2012-10-31 20:14 ` Michal Hocko
[not found] ` <20121031201415.GG1271-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2012-10-31 20:24 ` Tejun Heo
2012-10-31 20:24 ` Tejun Heo
[not found] ` <20121031202400.GT2945-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2012-10-31 20:49 ` Michal Hocko
2012-10-31 20:49 ` Michal Hocko
2012-10-31 20:49 ` Michal Hocko
2012-11-02 10:01 ` Kamezawa Hiroyuki
2012-11-02 10:01 ` Kamezawa Hiroyuki
2012-10-31 20:12 ` Michal Hocko
2012-10-31 20:12 ` Michal Hocko
[not found] ` <20121031201227.GF1271-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2012-10-31 20:14 ` Tejun Heo
2012-10-31 20:14 ` Tejun Heo
2012-10-31 20:14 ` Tejun Heo
[not found] ` <CAOS58YOHjLyKFeah+h+qOrAWvfi1O5eL7m-AMbqAdcP=EOFb6g-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2012-10-31 21:23 ` Michal Hocko
2012-10-31 21:23 ` Michal Hocko
2012-11-05 5:34 ` Li Zefan
2012-11-05 5:34 ` Li Zefan
2012-11-05 5:34 ` Li Zefan
2012-10-31 19:44 ` [PATCH 2/8] cgroup: kill CSS_REMOVED Tejun Heo
2012-10-31 19:44 ` Tejun Heo
[not found] ` <1351712650-23709-3-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-11-02 10:02 ` Kamezawa Hiroyuki
2012-11-02 10:02 ` Kamezawa Hiroyuki
2012-11-02 10:02 ` Kamezawa Hiroyuki
2012-11-05 5:33 ` Li Zefan
2012-11-05 5:33 ` Li Zefan
2012-11-05 5:33 ` Li Zefan
2012-10-31 19:44 ` Tejun Heo
2012-10-31 19:44 ` [PATCH 3/8] cgroup: use cgroup_lock_live_group(parent) in cgroup_create() Tejun Heo
2012-10-31 19:44 ` Tejun Heo
[not found] ` <1351712650-23709-4-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-11-02 10:03 ` Kamezawa Hiroyuki
2012-11-02 10:03 ` Kamezawa Hiroyuki
2012-11-05 5:36 ` Li Zefan
2012-11-05 5:36 ` Li Zefan
2012-11-05 5:36 ` Li Zefan
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 19:44 ` [PATCH 5/8] cgroup: remove CGRP_WAIT_ON_RMDIR, cgroup_exclude_rmdir() and cgroup_release_and_wakeup_rmdir() Tejun Heo
2012-10-31 19:44 ` Tejun Heo
[not found] ` <1351712650-23709-6-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-11-02 10:20 ` Kamezawa Hiroyuki
2012-11-02 10:20 ` Kamezawa Hiroyuki
2012-11-02 10:20 ` Kamezawa Hiroyuki
2012-11-05 5:40 ` Li Zefan
2012-11-05 5:40 ` Li Zefan
2012-11-05 5:40 ` Li Zefan
2012-10-31 19:44 ` [PATCH 6/8] memcg: make mem_cgroup_reparent_charges non failing Tejun Heo
2012-10-31 19:44 ` Tejun Heo
[not found] ` <1351712650-23709-7-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-11-02 10:21 ` Kamezawa Hiroyuki
2012-11-02 10:21 ` Kamezawa Hiroyuki
2012-10-31 19:44 ` [PATCH 7/8] hugetlb: do not fail in hugetlb_cgroup_pre_destroy Tejun Heo
2012-10-31 19:44 ` Tejun Heo
[not found] ` <1351712650-23709-8-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-11-02 10:23 ` Kamezawa Hiroyuki
2012-11-02 10:23 ` Kamezawa Hiroyuki
2012-11-02 10:23 ` Kamezawa Hiroyuki
2012-10-31 19:44 ` [PATCH 8/8] cgroup: make ->pre_destroy() return void Tejun Heo
2012-11-05 17:30 ` [PATCHSET RESEND v2] cgroup: simplify cgroup removal path Tejun Heo
2012-11-05 17:30 ` Tejun Heo
[not found] ` <20121105173024.GA19354-9pTldWuhBndy/B6EtB590w@public.gmane.org>
2012-11-05 18:39 ` Michal Hocko
2012-11-05 18:39 ` Michal Hocko
2012-11-05 17:30 ` Tejun Heo
-- strict thread matches above, loose matches on Subject: below --
2012-10-31 18:16 [PATCHSET " Tejun Heo
[not found] ` <1351707391-22287-1-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-10-31 18:16 ` [PATCH 1/8] cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs Tejun Heo
2012-10-31 18:16 ` Tejun Heo
[not found] ` <1351707391-22287-2-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-10-31 19:02 ` Michal Hocko
2012-10-31 19:02 ` Michal Hocko
2012-10-31 4:22 [PATCHSET] cgroup: simplify cgroup removal path Tejun Heo
[not found] ` <1351657365-25055-1-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-10-31 4:22 ` [PATCH 1/8] cgroup: kill cgroup_subsys->__DEPRECATED_clear_css_refs Tejun Heo
2012-10-31 4:22 ` Tejun Heo
[not found] ` <1351657365-25055-2-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2012-10-31 13:21 ` Glauber Costa
2012-10-31 13:21 ` Glauber Costa
2012-10-31 13:21 ` Glauber Costa
[not found] ` <509125D9.8070100-bzQdu9zFT3WakBO8gow8eQ@public.gmane.org>
2012-10-31 16:38 ` Tejun Heo
2012-10-31 16:38 ` Tejun Heo
2012-10-31 14:37 ` Michal Hocko
2012-10-31 14:37 ` Michal Hocko
2012-10-31 14:37 ` Michal Hocko
[not found] ` <20121031143751.GA22809-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2012-10-31 16:41 ` Tejun Heo
2012-10-31 16:41 ` Tejun Heo
[not found] ` <20121031164123.GD2945-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2012-10-31 16:48 ` Michal Hocko
2012-10-31 16:48 ` Michal Hocko
[not found] ` <20121031164855.GI22809-2MMpYkNvuYDjFM9bn6wA6Q@public.gmane.org>
2012-10-31 17:22 ` Tejun Heo
2012-10-31 17:22 ` Tejun Heo
2012-10-31 16:41 ` Tejun Heo
2012-11-02 9:23 ` Kamezawa Hiroyuki
2012-11-02 9:23 ` Kamezawa Hiroyuki
2012-11-02 9:23 ` Kamezawa Hiroyuki
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