linux-kernel - Re: [PATCH 6/9] cgroup_freezer: make freezer->state mask of flags

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Message-ID: <20121108143952.GD12973@htj.dyndns.org>
Date:	Thu, 8 Nov 2012 06:39:52 -0800
From:	Tejun Heo <tj@...nel.org>
To:	Michal Hocko <mhocko@...e.cz>
Cc:	lizefan@...wei.com, 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 6/9] cgroup_freezer: make freezer->state mask of flags

Hello, Michal.

On Thu, Nov 08, 2012 at 11:39:28AM +0100, Michal Hocko wrote:
> On Sat 03-11-12 01:38:32, Tejun Heo wrote:
> > freezer->state was an enum value - one of THAWED, FREEZING and FROZEN.
> > As the scheduled full hierarchy support requires more than one
> > freezing condition, switch it to mask of flags.  If FREEZING is not
> > set, it's thawed.  FREEZING is set if freezing or frozen.  If frozen,
> > both FREEZING and FROZEN are set.  Now that tasks can be attached to
> > an already frozen cgroup, this also makes freezing condition checks
> > more natural.
> > 
> > This patch doesn't introduce any behavior change.
> > 
> > Signed-off-by: Tejun Heo <tj@...nel.org>
> 
> I think it would be nicer to use freezer_state_flags enum rather than
> unsigned int for the state. I would even expect gcc to complain about
> that but it looks like -fstrict-enums is c++ specific (so long enum
> safety).

But if you use it as flag bits, the resulting value no longer is
inside the defined enum values.  Isn't that weird?

Thanks.

-- 
tejun
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