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

[Pavel Emelianov]

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
this can happen, so I believe application are (have to be) somehow
prepared to this.

> C.
>