[Devel] Re: [PATCH 11/13] Changes to show virtual ids to user

[Eric W. Biederman]

Pavel Emelianov <xemul at openvz.org> writes:

> Pavel Emelianov wrote:
>> Cedric Le Goater wrote:
>>> Hello !
>>>
>>>>>> The worst case I can see with pid == 0.  Is that it would be a bug
>>>>>> that we can fix later.  For other cases it would seem to be a user
>>>>>> space API thing that we get stuck with for all time.
>>>>> We cannot trust userspace application to expect some pid other than
>>>>> positive. All that we can is either use some always-absent pid or
>>>>> send the signal as SI_KERNEL.
>>>>>
>>>>> Our experience show that making decisions like above causes random
>>> <>> applications failures that are hard (or even impossible) to debug.
>>>
>>>> Ok.  So I guess I see what you are proposing is picking an arbitrary
>>>> pid, say pid == 2, and reserving that in all pid namespaces and using
>>>> it when we have a pid that does not map to a specific namespace. I'm
>>>> fine with that.
>>>>
>>>> All I care about is that we have a solution, preferably simple,
>>>> to the non-mapped pid problem.
>>> Pavel, are you against using pid == 0 and setting si_code to SI_KERNEL ? 
>> 
>> I think I am. A quick grep through the code revealed one place where
>
> Sorry. I have misprinted. I meant "I think I am *NOT*". My bad :(
>
>> this can happen, so I believe application are (have to be) somehow
>> prepared to this.

Where was this.  I'd like to follow your complete line of thinking.

Eric