Re: [PATCH] Update comment on find_task_by_pid_ns

Oleg Nesterov
2010-02-08T17:17:37Z

On 02/08, Thomas Gleixner wrote:
>
> On Mon, 8 Feb 2010, Oleg Nesterov wrote:
>
> > IOW, if we change copy_process()
> >
> > --- kernel/fork.c
> > +++ kernel/fork.c
> > @@ -1304,8 +1304,11 @@ static struct task_struct *copy_process(
> > return p;
> >
> > bad_fork_free_pid:
> > - if (pid != &init_struct_pid)
> > + if (pid != &init_struct_pid) {
> > + read_lock(&tasklist_lock);
> > free_pid(pid);
> > + read_unlock(&tasklist_lock);
> > + }
> > bad_fork_cleanup_io:
> > if (p->io_context)
> > exit_io_context(p);
> >
> > then find_task_by_pid_ns/etc could be used under tasklist safely even
> > with PREEMPT_RCU.
>
> We try to get rid of the read_lock sites of tasklist_lock, so please
> let's not think about adding more :)

Yes, yes, I agree. I didn't mean this patch makes sense.

Oleg.