[Devel] Re: [PATCH 1/15] Move exit_task_namespaces()

[Pavel Emelyanov]

Oleg Nesterov wrote:
> On 08/06, Pavel Emelyanov wrote:
>> Oleg Nesterov wrote:
>>> On 08/06, Pavel Emelyanov wrote:
>>>> Oleg Nesterov wrote:
>>>>> On 08/06, Pavel Emelyanov wrote:
>>>>>> Oleg Nesterov wrote:
>>>>>>> On 07/26, Pavel Emelyanov wrote:
>>>>>>>> The reason to release namespaces after reparenting is that when task
>>>>>>>> exits it may send a signal to its parent (SIGCHLD), but if the parent
>>>>>>>> has already exited its namespaces there will be no way to decide what
>>>>>>>> pid to dever to him - parent can be from different namespace.
>>>>>>> I almost forgot about this one...
>>>>>>>
>>> I guess I missed something stupid and simple...
>> In other words. Let task X live in init_pid_ns, task Y is his child and 
>> lives
>> int another namespace. task X and task Y both die. This will happen:
>>
>> 1. Task X call exit_task_namespaces() 
>>   and sets its nsproxy to NULL
> 
> Ah, got it, thanks. So the problem is not namespace itself (parent's or
> child's), there are still valid (even if different but related).
> 
> We just can't get ->parent->nsproxy. I was greatly confused by the "parent
> can be from different namespace" above. We have exactly same problem if
> namespaces are not differ.
> 
> IOW, the problem is: we can't clear ->nsproxy (exit_task_namespaces) until
> we get rid of ->children. This have nothing to do with different namespace.

No. If the parent is always in the same namespace we do not need to
get its nsproxy :) Problem is exactly in that the parent's namespace
is to be known.

> Oleg.
> 
>