On Tue, 24 Aug 2010 10:14:25 +0900
Daisuke Nishimura <nishimura@xxxxxxxxxxxxxxxxx> wrote:
> > > > @@ -723,6 +729,11 @@ static inline bool mem_cgroup_is_root(st
> > > > return (mem == root_mem_cgroup);
> > > > }
> > > >
> > > > +static inline bool mem_cgroup_is_rootid(unsigned short id)
> > > > +{
> > > > + return (id == 1);
> > > > +}
> > > > +
> > > It might be better to add
> > >
> > > BUG_ON(newid->id != 1)
> > >
> > > in cgroup.c::cgroup_init_idr().
> > >
> >
> > Why ??
> >
> Just to make sure that the root css has id==1. mem_cgroup_is_rootid() make
> use of the fact.
> I'm sorry if I miss something.
>
Hmm. The function allocating ID does
4530 static struct css_id *get_new_cssid(struct cgroup_subsys *ss, int depth)
4531 {
==
4546 spin_lock(&ss->id_lock);
4547 /* Don't use 0. allocates an ID of 1-65535 */
4548 error = idr_get_new_above(&ss->idr, newid, 1, &myid);
4549 spin_unlock(&ss->id_lock);
==
and allocates ID above "1", always.
Adding BUG_ON(newid->id != 1) will mean that we doubt the bitmap function and
consider possibility that new->id == 0.
But, we're 100% sure that it never happens.
I don't think adding a comment is a right thing to do.
Thanks,
-Kame
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