From: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
To: Frederic Weisbecker <fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
Cc: Containers
<containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>,
LKML <linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>,
Mandeep Singh Baines
<msb-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>,
Cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
Paul Menage <paul-inf54ven1CmVyaH7bEyXVA@public.gmane.org>
Subject: Re: [PATCH 2/2 v3] cgroup: Drop task_lock(parent) on cgroup_fork()
Date: Wed, 21 Dec 2011 11:16:24 -0800 [thread overview]
Message-ID: <20111221191624.GK9213@google.com> (raw)
In-Reply-To: <1324494199-23928-3-git-send-email-fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
On Wed, Dec 21, 2011 at 08:03:19PM +0100, Frederic Weisbecker wrote:
> We don't need to hold the parent task_lock() on the
> parent in cgroup_fork() because we are already synchronized
> against the two places that may change the parent css_set
> concurrently:
>
> - cgroup_exit(), but the parent obviously can't exit concurrently
> - cgroup migration: we are synchronized against threadgroup_lock()
>
> So we can safely remove the task_lock() there.
>
> Signed-off-by: Frederic Weisbecker <fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> Cc: Tejun Heo <tj-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> Cc: Li Zefan <lizf-BthXqXjhjHXQFUHtdCDX3A@public.gmane.org>
> Cc: Containers <containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>
> Cc: Cgroups <cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu-+CUm20s59erQFUHtdCDX3A@public.gmane.org>
> Cc: Oleg Nesterov <oleg-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
> Cc: Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
> Cc: Paul Menage <paul-inf54ven1CmVyaH7bEyXVA@public.gmane.org>
> Cc: Mandeep Singh Baines <msb-F7+t8E8rja9g9hUCZPvPmw@public.gmane.org>
Applied both patches to cgroup/for-3.3 and pushed out to linux-next.
Thank you.
--
tejun
WARNING: multiple messages have this Message-ID (diff)
From: Tejun Heo <tj@kernel.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Li Zefan <lizf@cn.fujitsu.com>,
LKML <linux-kernel@vger.kernel.org>,
Containers <containers@lists.linux-foundation.org>,
Cgroups <cgroups@vger.kernel.org>,
KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>,
Oleg Nesterov <oleg@redhat.com>,
Andrew Morton <akpm@linux-foundation.org>,
Paul Menage <paul@paulmenage.org>,
Mandeep Singh Baines <msb@chromium.org>
Subject: Re: [PATCH 2/2 v3] cgroup: Drop task_lock(parent) on cgroup_fork()
Date: Wed, 21 Dec 2011 11:16:24 -0800 [thread overview]
Message-ID: <20111221191624.GK9213@google.com> (raw)
In-Reply-To: <1324494199-23928-3-git-send-email-fweisbec@gmail.com>
On Wed, Dec 21, 2011 at 08:03:19PM +0100, Frederic Weisbecker wrote:
> We don't need to hold the parent task_lock() on the
> parent in cgroup_fork() because we are already synchronized
> against the two places that may change the parent css_set
> concurrently:
>
> - cgroup_exit(), but the parent obviously can't exit concurrently
> - cgroup migration: we are synchronized against threadgroup_lock()
>
> So we can safely remove the task_lock() there.
>
> Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
> Cc: Tejun Heo <tj@kernel.org>
> Cc: Li Zefan <lizf@cn.fujitsu.com>
> Cc: Containers <containers@lists.linux-foundation.org>
> Cc: Cgroups <cgroups@vger.kernel.org>
> Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com>
> Cc: Oleg Nesterov <oleg@redhat.com>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Paul Menage <paul@paulmenage.org>
> Cc: Mandeep Singh Baines <msb@chromium.org>
Applied both patches to cgroup/for-3.3 and pushed out to linux-next.
Thank you.
--
tejun
next prev parent reply other threads:[~2011-12-21 19:16 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-12-21 19:03 [PATCH 0/2 v3] cgroup: Remove useless task_lock() Frederic Weisbecker
2011-12-21 19:03 ` Frederic Weisbecker
[not found] ` <1324494199-23928-1-git-send-email-fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2011-12-21 19:03 ` [PATCH 1/2 v3] cgroup: Remove unnecessary task_lock before fetching css_set on migration Frederic Weisbecker
2011-12-21 19:03 ` Frederic Weisbecker
2011-12-21 19:03 ` [PATCH 2/2 v3] cgroup: Drop task_lock(parent) on cgroup_fork() Frederic Weisbecker
2011-12-21 19:03 ` Frederic Weisbecker
[not found] ` <1324494199-23928-3-git-send-email-fweisbec-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
2011-12-21 19:16 ` Tejun Heo [this message]
2011-12-21 19:16 ` Tejun Heo
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