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Date: Wed, 04 Jun 2008 18:20:18 +0900
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: "Paul Menage" <menage@google.com>
Subject: Re: [PATCH] cgroup: list_for_each cleanup
Cc: kosaki.motohiro@jp.fujitsu.com, linux-kernel@vger.kernel.org,
       "Li Zefan" <lizf@cn.fujitsu.com>
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References: <20080604172812.941C.KOSAKI.MOTOHIRO@jp.fujitsu.com> <6599ad830806040211t31d86c57o6836f7cc34faf7f7@mail.gmail.com>
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> > -       while (!list_empty(&release_list)) {
> > +
> > +       list_for_each_entry_safe(cgrp, saved_cgrp, &release_list,
> > +                                release_list) {
> >                char *argv[3], *envp[3];
> >                int i;
> >                char *pathbuf;
> > -               struct cgroup *cgrp = list_entry(release_list.next,
> > -                                                   struct cgroup,
> > -                                                   release_list);
> > +
> 
> I don't think that list_for_each_entry_safe() is still safe when we've
> dropped release_list_lock. saved_cgroup could end up pointing to a
> cgroup that's freed while we're forking the usermode helper.

Ah, you are right.
I'll drop this portion and resend patch.

Thanks.