linux-kernel - Re: [PATCH 8/9] cgroup_freezer: add ->post_create() and ->pre

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Date:	Thu, 08 Nov 2012 13:48:25 +0900
From:	Kamezawa Hiroyuki <kamezawa.hiroyu@...fujitsu.com>
To:	Tejun Heo <tj@...nel.org>
CC:	lizefan@...wei.com, mhocko@...e.cz, rjw@...k.pl,
	containers@...ts.linux-foundation.org, cgroups@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-pm@...r.kernel.org,
	fweisbec@...il.com
Subject: Re: [PATCH 8/9] cgroup_freezer: add ->post_create() and ->pre_destroy()
 and track online state

(2012/11/03 17:38), Tejun Heo wrote:
> A cgroup is online and visible to iteration between ->post_create()
> and ->pre_destroy().  This patch introduces CGROUP_FREEZER_ONLINE and
> toggles it from the newly added freezer_post_create() and
> freezer_pre_destroy() while holding freezer->lock such that a
> cgroup_freezer can be reilably distinguished to be online.  This will
> be used by full hierarchy support.
> 
> ONLINE test is added to freezer_apply_state() but it currently doesn't
> make any difference as freezer_write() can only be called for an
> online cgroup.
> 
> Adjusting system_freezing_cnt on destruction is moved from
> freezer_destroy() to the new freezer_pre_destroy() for consistency.
> 
> This patch doesn't introduce any noticeable behavior change.
> 
> Signed-off-by: Tejun Heo <tj@...nel.org>
> ---
>   kernel/cgroup_freezer.c | 42 ++++++++++++++++++++++++++++++++++++++++--
>   1 file changed, 40 insertions(+), 2 deletions(-)
> 
> diff --git a/kernel/cgroup_freezer.c b/kernel/cgroup_freezer.c
> index b8ad93c..4f12d31 100644
> --- a/kernel/cgroup_freezer.c
> +++ b/kernel/cgroup_freezer.c
> @@ -23,6 +23,7 @@
>   #include <linux/seq_file.h>
>   
>   enum freezer_state_flags {
> +	CGROUP_FREEZER_ONLINE	= (1 << 0), /* freezer is fully online */

Could you explain what 'online' means here again, rather than changelog ?
BTW, 'online' is a shared concept, between post_create() and pre_destroy(), among
developpers ? Is it new ?

Anyway, the patch itself is simple.

Reviewed-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>


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