Re: [PATCH] cgroup: fix a race condition in manipulatingtsk->cg_list

From: Andrew Morton
Date: Thu Apr 17 2008 - 01:17:23 EST


On Thu, 17 Apr 2008 13:04:47 +0800 Li Zefan <lizf@xxxxxxxxxxxxxx> wrote:

> >
> > Yes, that looks like it could be the same one - great. But this
> > corruption can only be triggered the first time you cat a tasks file
> > after a reboot, right? That would partly explain why it was hard to
> > reproduce (at least, I had trouble).
> >
>
> Right. I was lucky to trigger this and thus knew how to reproduce.
>
> > My only thought about the downside of this is that an exiting task
> > that gets stuck somewhere between setting PF_EXITING and calling
> > cgroup_exit() won't show up in its cgroup's tasks file, since we'll
> > enable cgroup links but skip it. I guess that's not a big deal.
> >
>
> Agree. I think it won't be a problem.
>
> > Maybe it would be better to not do a cgroup_exit() until we're
> > unhashed, so that cgroup_enable_task_cg_list() can't find the exiting
> > task?

So we won't be doing what Paul suggested?
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