[PATCH v2] /proc/pid/status: show all sets of pid according to ns

[Richard Weinberger]

Am 29.05.2014 11:41, schrieb Pavel Emelyanov:
> On 05/29/2014 01:21 PM, Richard Weinberger wrote:
>> Am 29.05.2014 11:07, schrieb Pavel Emelyanov:
>>> On 05/29/2014 09:59 AM, Vasily Kulikov wrote:
>>>> On Wed, May 28, 2014 at 23:27 +0400, Pavel Emelyanov wrote:
>>>>> On 05/28/2014 10:28 PM, Vasily Kulikov wrote:
>>>>>> On Wed, May 28, 2014 at 16:44 +0400, Pavel Emelyanov wrote:
>>>>>> It will be simplier
>>>>>> to parse the file -- if 'ns_ids' file contains some ID then this ID for
>>>>>> every ns can be obtained regardless of the specific ID name (SID, PID,
>>>>>> PGID, etc.).
>>>>>
>>>>> True, but given a task PID how to determine which pid namespaces it lives in
>>>>> to get the idea of how PIDs map to each other? Maybe we need some explicit
>>>>> API for converting (ID, NS1, NS2) into (ID)?
>>>>
>>>> AFAIU the idea of the patch is to add a new debugging information which
>>>> can be trivially obtained via 'cat /proc/...':
>>>
>>> I agree, but this ability will be very useful by checkpoint-restore project
>>> too and I'd really appreciate if the API we have for that would be scalable
>>> enough. Per-task proc file works for me, but how about sid-s and pgid-s?
>>
>> What kind of information does CRIU need?
> 
> We need to know what pid namespaces a task lives in and how pid, sid and
> pgid look in all of them. A short example with pids only

So use case is to checkpoint/restore nested containers? :)

Thanks,
//richard