Re: [PATCH 4/5] pidfd: add CLONE_WAIT_PID

[Christian Brauner]

On Thu, Jul 25, 2019 at 12:30:48PM +0200, Oleg Nesterov wrote:
> On 07/24, Jann Horn wrote:
> >
> > --- a/kernel/fork.c
> > +++ b/kernel/fork.c
> > @@ -1902,6 +1902,10 @@ static __latent_entropy struct task_struct *copy_process(
> >         delayacct_tsk_init(p);  /* Must remain after dup_task_struct() */
> >         p->flags &= ~(PF_SUPERPRIV | PF_WQ_WORKER | PF_IDLE);
> >         p->flags |= PF_FORKNOEXEC;
> > +       if (!(clone_flags & CLONE_THREAD))
> > +               p->flags &= ~PF_PF_WAIT_PID;
> > +       if (clone_flags & CLONE_WAIT_PID)
> > +               p->flags |= PF_PF_WAIT_PID;
> 
> agreed, but then the "if (!thread_group_leader(tsk))" block in de_thread()
> should also copy PF_PF_WAIT_PID.
> 
> > An alternative would be to not use p->flags at all, but instead make
> > this a property of the signal_struct - since the property is shared by
> > all threads, that might make more sense?
> 
> I tend to agree.

Hm, ok. That's two people that prefer to make this a flag in
signal_struct. Ok, let me adapt the patch.

Thanks!
Christian