On 06/25, Andy Lutomirski wrote: > > On Tue, Jun 25, 2013 at 2:52 PM, Cyrill Gorcunov <gorcu...@gmail.com> wrote: > > On Tue, Jun 25, 2013 at 02:36:31PM -0700, Andy Lutomirski wrote: > >> On Tue, Jun 25, 2013 at 1:17 PM, Oleg Nesterov <o...@redhat.com> wrote: > >> > On 06/26, Cyrill Gorcunov wrote: > >> >> > >> >> On Tue, Jun 25, 2013 at 12:51:45PM -0700, Andy Lutomirski wrote: > >> >> > This is currently only available if CONFIG_CHECKPOINT_RESTORE, which > >> >> > is hidden under CONFIG_EXPERT. It's generally useful functionality, > >> >> > though, so expose it unconditionally. > >> >> > > >> >> > Cc: Cyrill Gorcunov <gorcu...@openvz.org> > >> >> > Signed-off-by: Andy Lutomirski <l...@amacapital.net> > >> >> Acked-by: Cyrill Gorcunov <gorcu...@openvz.org> > >> > > >> > I didn't see the patch but I guess it is trivial and I agree with intent > >> > ;) > >> > >> The patch works, but "children" is only listed under task/<tid>, not > >> under /proc/<pid>. Is that intentional? Fixing it would be a > >> one-liner. > > > > Yeah, it's intentional. Here some explanations from Oleg (check out > > the whole thread, it's not that big https://lkml.org/lkml/2011/12/9/220) > > in short this might require some more code, but i'll re-check tomorrow. > > This is a little strange. It looks like ppid (in status) shows the > tgid,
Yes, > but the actual real_parent can refer to a thread (as opposed to > a thread group leader), Yes. This is mostly the internal implementation detail. And probably it would be nice to move ->children from task_struct to signal_struct. However. See __WNOTHREAD in man waitpid. I think this is the only (historical) reason. Otherwise the real_parent's tid doesn't matter, the parent is always the whole process, not sub-thread. > and task/tid/children respects that. Well, it should respect if you want to restart and keep __WNOTHREAD working. But there is another reason. It is not trivial to list all children under /proc/<pid>, and the fix would not be a one-liner ;) You need to fight with the exiting sub-threads and reparenting. > So the > tree that you get by following task/tid/ children won't be quite the > same as the tree you get by following ppid. Not sure I understand... but in any case, yes you need to read /proc/pid/task/*/children to construct the tree. > I wonder if the ptid should be added to status. Is there anything > (other than task/tid/children) Perhaps, I dunno. Better yet, we should kill __WNOTHREAD ;) I am wondering if it is still used. Oleg. -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
