On 09/01, Oleg Nesterov wrote:
>
> On 08/31, sukadev@xxxxxxxxxx wrote:
> >
> > +static struct pid_namespace *get_task_pid_ns(struct task_struct *tsk)
> > +{
> > + struct pid *pid;
> > + struct pid_namespace *ns;
> > +
> > + pid = get_task_pid(tsk, PIDTYPE_PID);
> > + ns = get_pid_ns(pid_active_ns(pid));
> > + put_pid(pid);
> > +
> > + return ns;
> > +}
>
> Hmm. Firstly, we don't need this for the "current", but all users of this func
> also do get_task_pid_ns(current).
>
> Also, we don't need get/put_pid. rcu locks are enough,
>
> rcu_read_lock();
> ns = get_pid_ns(pid_active_ns(task_pid(tks)));
> rcu_read_unlock();
>
> However, do we really need this complications right now? Currently, we use
> this "compare namespaces" helpers only when we know that "struct pid" is
> stable. We are sending the signal to that task, it must be pid_alive(), and
> we either locked the task itself, or we hold tasklist.
(forgot to mention)
Otherwise, it is not safe to use "tsk" in get_task_pid_ns(), so I don't think
these get/put pid/pid_ns games make too much sense.
Oleg.
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