[Devel] Re: [RFC][PATCH] Make access to taks's nsproxy liter

[Oleg Nesterov]

On 08/08, Serge E. Hallyn wrote:
>
> Quoting Pavel Emelyanov (xemul at openvz.org):
> > +void switch_task_namespaces(struct task_struct *p, struct nsproxy *new)
> > +{
> > +	struct nsproxy *ns;
> > +
> > +	might_sleep();
> > +
> > +	ns = p->nsproxy;
> > +	if (ns == new)
> > +		return;
> > +
> > +	if (new)
> > +		get_nsproxy(new);
> > +	rcu_assign_pointer(p->nsproxy, new);
> > +
> > +	if (ns && atomic_dec_and_test(&ns->count)) {
> > +		/*
> > +		 * wait for others to get what they want from this
> > +		 * nsproxy. cannot release this nsproxy via the
> > +		 * call_rcu() since put_mnt_ns will want to sleep
> > +		 */
> > +		synchronize_rcu();
> > +		free_nsproxy(ns);
> > +	}
> > +}
> 
> Also a comment above switch_task_namespaces() that it must be called
> with task_lock held.

Heh, indeed, sys_unshare() does this. might_sleep() won't be happy.

Oleg.

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