Messages in this thread | | | Date | Tue, 17 Jan 2012 21:57:25 +0400 | From | Cyrill Gorcunov <> | Subject | Re: [RFC] fs, proc: Introduce /proc/<pid>/task/<tid>/children entry v6 |
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On Tue, Jan 17, 2012 at 06:40:49PM +0100, Oleg Nesterov wrote: ... > > > > > > But this is not enough. exit_ptrace() can do list_move() without > > > changing ->real_parent. > > > > > > I'll try to think. At first glance we can rely on EXIT_DEAD, but > > > I'd like to avoid this, I think EXIT_DEAD should die. > > > > Ouch! Thanks for catching this Oleg. I'll try to come with something > > to show as well. > > Do you see another approach? I don't, so I'd suggest to check > "task->exit_state != EXIT_DEAD" instead of !list_empty(). >
Well, I thought what if I can find another way without EXIT_DEAD but seems there is no luck.
> Just in case, we can also check "start->exit_state == 0" instead > of "task->real_parent == start" with the same effect, up to you. >
real_parent == start somehow more informative for me so if you allow (and noone against) I would leave the current form.
> It would be nice to add the comment explaining these checks... >
Yeah, I'll add ones. Sure.
> And I forgot to mention, the comment below > > > + /* > > + * We might miss some freshly created children > > + * here, but it was never promised to be > > + * accurate. > > + */ > > + if (list_is_last(&task->sibling, &start->children)) > > + goto out; > > looks misleading. Contrary to the slow path, we can't miss the > freshly forked child here, copy_process() does list_add_tail(). >
Ah, crap, indeed!
> But the slow path obviously can skip much more than needed and > miss children (freshly forked or not), probably it would be better > to move the comment down and remove the "freshly created" part. > > What do you think? > >
Yeah, thanks a lot, Oleg. I'll update it an post for review (I hope to finish it tonight ;)
Cyrill
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