From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Li Zefan <lizefan-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Cc: shyju pv <shyju.pv-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>,
Sanil kumar <sanil.kumar-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>,
Masanari Iida
<standby24x7-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>,
LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org,
levinsasha928-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
Subject: Re: [PATCH] cgroup: fix dentry still in use bug when dropping css refs after umount
Date: Mon, 16 Jul 2012 09:45:27 -0700 [thread overview]
Message-ID: <20120716164527.GB30872@google.com> (raw)
In-Reply-To: <4FFB8F39.9030209-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Hello,
On Tue, Jul 10, 2012 at 10:11:05AM +0800, Li Zefan wrote:
> Right, but that should be safe. The css objects of the root cgroup are
> allocated at boot, and won't be destroyed at umount.
>
> Furthermore when a cgroup hierarchy is going to be unmounted, those css's
> will be made to point to a cgroup named dummytop in rebind_subsystems(),
> and there's a syncronize_rcu() in the end of the function, so accessing
> css->cgroup is always safe.
>
> In this case, dummytop->dentry is NULL, and that's safe too, because
> cgroup_path() is aware of this case.
I see. Thanks for the explanation.
--
tejun
WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj@kernel.org>
To: Li Zefan <lizefan@huawei.com>
Cc: shyju pv <shyju.pv@huawei.com>,
Sanil kumar <sanil.kumar@huawei.com>,
Masanari Iida <standby24x7@gmail.com>,
LKML <linux-kernel@vger.kernel.org>,
Cgroups <cgroups@vger.kernel.org>,
viro@zeniv.linux.org.uk, levinsasha928@gmail.com
Subject: Re: [PATCH] cgroup: fix dentry still in use bug when dropping css refs after umount
Date: Mon, 16 Jul 2012 09:45:27 -0700 [thread overview]
Message-ID: <20120716164527.GB30872@google.com> (raw)
In-Reply-To: <4FFB8F39.9030209@huawei.com>
Hello,
On Tue, Jul 10, 2012 at 10:11:05AM +0800, Li Zefan wrote:
> Right, but that should be safe. The css objects of the root cgroup are
> allocated at boot, and won't be destroyed at umount.
>
> Furthermore when a cgroup hierarchy is going to be unmounted, those css's
> will be made to point to a cgroup named dummytop in rebind_subsystems(),
> and there's a syncronize_rcu() in the end of the function, so accessing
> css->cgroup is always safe.
>
> In this case, dummytop->dentry is NULL, and that's safe too, because
> cgroup_path() is aware of this case.
I see. Thanks for the explanation.
--
tejun
next prev parent reply other threads:[~2012-07-16 16:45 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-06-30 7:07 [PATCH] cgroup: fix dentry still in use bug when dropping css refs after umount Li Zefan
2012-06-30 7:07 ` Li Zefan
2012-06-30 14:34 ` Masanari Iida
[not found] ` <4FEEA5CB.8070809-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2012-07-03 17:03 ` Tejun Heo
2012-07-03 17:03 ` Tejun Heo
[not found] ` <20120703170317.GB555-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-07-03 22:52 ` Tejun Heo
2012-07-03 22:52 ` Tejun Heo
[not found] ` <20120703225218.GF555-hpIqsD4AKlfQT0dZR+AlfA@public.gmane.org>
2012-07-04 6:19 ` Li Zefan
2012-07-04 6:19 ` Li Zefan
[not found] ` <4FF3E063.5010604-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2012-07-08 6:35 ` Tejun Heo
2012-07-08 6:35 ` Tejun Heo
[not found] ` <20120708063536.GB19021-RcKxWJ4Cfj1J2suj2OqeGauc2jM2gXBXkQQo+JxHRPFibQn6LdNjmg@public.gmane.org>
2012-07-10 2:11 ` Li Zefan
2012-07-10 2:11 ` Li Zefan
[not found] ` <4FFB8F39.9030209-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
2012-07-16 16:45 ` Tejun Heo [this message]
2012-07-16 16:45 ` Tejun Heo
[not found] ` <4ff55c60.27da440a.65ec.ffff83dfSMTPIN_ADDED@mx.google.com>
[not found] ` <4ff55c60.27da440a.65ec.ffff83dfSMTPIN_ADDED-ATjtLOhZ0NVl57MIdRCFDg@public.gmane.org>
2012-07-07 23:46 ` [PATCH 1/2] Revert "cgroup: superblock can't be released with active dentries" 'Tejun Heo'
2012-07-07 23:46 ` 'Tejun Heo'
[not found] ` <20120707234634.GC16783-RcKxWJ4Cfj1J2suj2OqeGauc2jM2gXBXkQQo+JxHRPFibQn6LdNjmg@public.gmane.org>
2012-07-07 23:46 ` [PATCH 2/2] cgroup: fix cgroup hierarchy umount race 'Tejun Heo'
2012-07-07 23:46 ` 'Tejun Heo'
[not found] ` <20120707234659.GD16783-RcKxWJ4Cfj1J2suj2OqeGauc2jM2gXBXkQQo+JxHRPFibQn6LdNjmg@public.gmane.org>
2012-07-14 12:08 ` Al Viro
2012-07-14 12:08 ` Al Viro
[not found] ` <20120714120852.GK22927-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2012-07-16 16:44 ` 'Tejun Heo'
2012-07-16 16:44 ` 'Tejun Heo'
2012-07-04 5:56 ` [PATCH] cgroup: fix dentry still in use bug when dropping css refs after umount Li Zefan
2012-07-04 5:56 ` Li Zefan
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