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From: Tejun Heo <tj@kernel.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: containers@lists.linux-foundation.org, lizf@cn.fujitsu.com,
	linux-kernel@vger.kernel.org,
	linux-pm@lists.linux-foundation.org, paul@paulmenage.org,
	kamezawa.hiroyu@jp.fujitsu.com
Subject: Re: [PATCH 6/6] cgroup: kill subsys->can_attach_task(), pre_attach() and attach_task()
Date: Thu, 1 Sep 2011 20:22:21 +0900	[thread overview]
Message-ID: <20110901112221.GA2752__2676.7247509726$1314929367$gmane$org@htj.dyndns.org> (raw)
In-Reply-To: <20110831134220.GB20598@somewhere>

Hello,

On Wed, Aug 31, 2011 at 03:42:24PM +0200, Frederic Weisbecker wrote:
> My task counter subsystem patchset brings a cancel_attach_task() callback
> that cancels can_attach_task() effects.
> 
> I thought that rebased on top of your patch it's going to be merged inside
> cancel_attach() but OTOH we can't cancel the effect of failed migration
> on a thread that way.
> 
> May be we need to keep a cancel_attach_task() just for that purpose?

We can do that but I think that becomes a bit too complex and fragile.
That path won't be traveled unless it races against exit.  Bugs will
be difficult to detect and reproduce.  In this respect, the current
code already seems racy.  ->can_attach (or other methods in the attach
path) and ->exit can race each other and I don't think all subsystems
handle that properly.

IMHO the right thing to do here is simplifying synchronization rules
so that nothing else happens while migration is in progress.

Thanks.

-- 
tejun

  parent reply	other threads:[~2011-09-01 11:22 UTC|newest]

Thread overview: 82+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-08-25 22:43 [PATCHSET] cgroup: introduce cgroup_taskset and consolidate subsys methods, take#2 Tejun Heo
2011-08-25 22:43 ` [PATCH 1/6] cgroup: subsys->attach_task() should be called after migration Tejun Heo
2011-08-25 22:43 ` Tejun Heo
2011-08-26  4:12   ` KAMEZAWA Hiroyuki
2011-08-26  4:12   ` KAMEZAWA Hiroyuki
     [not found]   ` <1314312192-26885-2-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2011-08-26  4:12     ` KAMEZAWA Hiroyuki
2011-08-25 22:43 ` [PATCH 2/6] cgroup: improve old cgroup handling in cgroup_attach_proc() Tejun Heo
2011-08-26  4:13   ` KAMEZAWA Hiroyuki
     [not found]   ` <1314312192-26885-3-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2011-08-26  4:13     ` KAMEZAWA Hiroyuki
2011-08-26  4:13   ` KAMEZAWA Hiroyuki
2011-08-25 22:43 ` Tejun Heo
2011-08-25 22:43 ` [PATCH 3/6] cgroup: introduce cgroup_taskset and use it in subsys->can_attach(), cancel_attach() and attach() Tejun Heo
2011-08-26  2:38   ` Matt Helsley
     [not found]   ` <1314312192-26885-4-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2011-08-26  2:38     ` Matt Helsley
2011-08-26  4:16     ` KAMEZAWA Hiroyuki
2011-08-26  2:38   ` Matt Helsley
2011-08-26  2:48     ` Matt Helsley
2011-08-26  2:48     ` Matt Helsley
2011-08-26  6:40     ` Tejun Heo
     [not found]     ` <20110826023818.GC3457-52DBMbEzqgQ/wnmkkaCWp/UQ3DHhIser@public.gmane.org>
2011-08-26  2:48       ` Matt Helsley
2011-08-26  6:40       ` Tejun Heo
2011-08-26 15:54       ` Paul Menage
2011-08-26  6:40     ` Tejun Heo
2011-08-26 15:54     ` Paul Menage
2011-08-26 15:54     ` Paul Menage
2011-08-26  4:16   ` KAMEZAWA Hiroyuki
2011-08-26  4:16   ` KAMEZAWA Hiroyuki
2011-08-25 22:43 ` Tejun Heo
2011-08-25 22:43 ` [PATCH 4/6] cgroup: don't use subsys->can_attach_task() or ->attach_task() Tejun Heo
2011-08-25 22:43 ` Tejun Heo
     [not found]   ` <1314312192-26885-5-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2011-08-26  4:18     ` KAMEZAWA Hiroyuki
2011-08-26  4:18   ` KAMEZAWA Hiroyuki
2011-08-26  4:18   ` KAMEZAWA Hiroyuki
2011-08-25 22:43 ` [PATCH 5/6] cgroup, cpuset: don't use ss->pre_attach() Tejun Heo
2011-08-25 22:43 ` Tejun Heo
     [not found]   ` <1314312192-26885-6-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2011-08-26  4:19     ` KAMEZAWA Hiroyuki
2011-08-26  4:19   ` KAMEZAWA Hiroyuki
2011-08-26  4:19   ` KAMEZAWA Hiroyuki
2011-08-25 22:43 ` [PATCH 6/6] cgroup: kill subsys->can_attach_task(), pre_attach() and attach_task() Tejun Heo
2011-08-26  4:20   ` KAMEZAWA Hiroyuki
2011-08-26  4:20   ` KAMEZAWA Hiroyuki
2011-08-30 20:10   ` Frederic Weisbecker
2011-08-31  7:03     ` Tejun Heo
2011-08-31 13:42       ` Frederic Weisbecker
2011-08-31 13:42       ` Frederic Weisbecker
2011-09-01 11:22         ` Tejun Heo
2011-09-01 11:22         ` Tejun Heo [this message]
2011-09-01 11:22         ` Tejun Heo
     [not found]           ` <20110901112221.GA2752-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2011-09-01 12:58             ` Frederic Weisbecker
2011-09-01 12:58           ` Frederic Weisbecker
2011-09-01 12:58           ` Frederic Weisbecker
     [not found]       ` <20110831070313.GA29179-9pTldWuhBndy/B6EtB590w@public.gmane.org>
2011-08-31 13:42         ` Frederic Weisbecker
     [not found]     ` <20110830201030.GC15953-oHC15RC7JGTpAmv0O++HtFaTQe2KTcn/@public.gmane.org>
2011-08-31  7:03       ` Tejun Heo
2011-08-31  7:03     ` Tejun Heo
     [not found]   ` <1314312192-26885-7-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2011-08-26  4:20     ` KAMEZAWA Hiroyuki
2011-08-30 20:10     ` Frederic Weisbecker
2011-08-30 20:10   ` Frederic Weisbecker
2011-08-25 22:43 ` Tejun Heo
     [not found] ` <1314312192-26885-1-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2011-08-25 22:43   ` [PATCH 1/6] cgroup: subsys->attach_task() should be called after migration Tejun Heo
2011-08-25 22:43   ` [PATCH 2/6] cgroup: improve old cgroup handling in cgroup_attach_proc() Tejun Heo
2011-08-25 22:43   ` [PATCH 3/6] cgroup: introduce cgroup_taskset and use it in subsys->can_attach(), cancel_attach() and attach() Tejun Heo
2011-08-25 22:43   ` [PATCH 4/6] cgroup: don't use subsys->can_attach_task() or ->attach_task() Tejun Heo
2011-08-25 22:43   ` [PATCH 5/6] cgroup, cpuset: don't use ss->pre_attach() Tejun Heo
2011-08-25 22:43   ` [PATCH 6/6] cgroup: kill subsys->can_attach_task(), pre_attach() and attach_task() Tejun Heo
2011-08-25 22:48   ` [PATCHSET] cgroup: introduce cgroup_taskset and consolidate subsys methods, take#2 Tejun Heo
2011-08-26  8:05   ` Li Zefan
2011-08-25 22:48 ` Tejun Heo
2011-08-25 22:48 ` Tejun Heo
2011-08-26  8:05 ` Li Zefan
2011-08-26  8:05 ` Li Zefan
2011-08-26 14:09   ` Tejun Heo
2011-08-26 14:56     ` Paul Menage
2011-08-26 14:56     ` Paul Menage
     [not found]     ` <20110826140900.GF2632-Gd/HAXX7CRxy/B6EtB590w@public.gmane.org>
2011-08-26 14:56       ` Paul Menage
2011-08-26 14:09   ` Tejun Heo
     [not found]   ` <4E5753D3.9080500-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
2011-08-26 14:09     ` Tejun Heo
  -- strict thread matches above, loose matches on Subject: below --
2011-08-23 22:19 [PATCHSET] cgroup: introduce cgroup_taskset and consolidate subsys methods Tejun Heo
2011-08-23 22:20 ` [PATCH 6/6] cgroup: kill subsys->can_attach_task(), pre_attach() and attach_task() Tejun Heo
2011-08-23 22:20 ` Tejun Heo
2011-08-25  9:45   ` Paul Menage
     [not found]   ` <1314138000-2049-7-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2011-08-25  9:45     ` Paul Menage
2011-08-25  9:45   ` Paul Menage
     [not found] ` <1314138000-2049-1-git-send-email-tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
2011-08-23 22:20   ` Tejun Heo

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