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SubjectRe: [PATCH 6/9] cgroup_freezer: make freezer->state mask of flags
Hello, Kamezawa.

On Thu, Nov 08, 2012 at 02:00:34PM +0900, Kamezawa Hiroyuki wrote:
> (2012/11/08 13:42), Tejun Heo wrote:
> >Hello, Kame.
> >
> >On Thu, Nov 08, 2012 at 01:37:50PM +0900, Kamezawa Hiroyuki wrote:
> >>How about
> >>enum {
> >> __CGROUP_FREEZING,
> >> __CGROUP_FROZEN,
> >>};
> >>
> >>#define CGROUP_FREEZER_STATE_MASK 0x3
> >>#define CGROUP_FREEZER_STATE(state) ((state) & CGROUP_FREEZER_STATE_MASK)
> >>#define CGROUP_THAW(state) (CGROUP_FREEZER_STATE(state) == 0)
> >>#define CGROUP_FREEZING(state) (CGROUP_FREEZER_STATE(state) == __CGROUP_FREEZING)
> >>#define CGROUP_FROZEN(state)\
> >> (CGROUP_FREEZER_STATE(state) == (__CGROUP_FREEZING | __CGROUP_FROZEN))
> >
> >I think it's a bit overdone and we have cases where we test for
> >FREEZING regardless of FROZEN and cases where test for FREEZING &&
> >!FROZEN. We can have, say, CGROUP_FREZING() and then
> >CGROUP_FREEZING_BUT_NOT_FROZEN(), but it feels more like obfuscation
> >than anything else.
> >
>
> Hm, then, I'm glad if I can see what combinations of flags are valid and
> meanings of them in source code comments.

Ooh, the following comment is added by a later patch when the whole
thing is complete.

/*
* A cgroup is freezing if any FREEZING flags are set. FREEZING_SELF is
* set if "FROZEN" is written to freezer.state cgroupfs file, and cleared
* for "THAWED". FREEZING_PARENT is set if the parent freezer is FREEZING
* for whatever reason. IOW, a cgroup has FREEZING_PARENT set if one of
* its ancestors has FREEZING_SELF set.
*/

Thanks.

--
tejun


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