Re: [RFC][PATCH 0/4] Object creation with a specified id

[Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>]

Oren Laadan wrote:
> 
> Pavel Emelyanov wrote:
>> Oren Laadan wrote:
>>> Nadia Derbey wrote:
>>>> Oren Laadan wrote:
>>>>> Nadia.Derbey-6ktuUTfB/bM@public.gmane.org wrote:
>>>>>
>>>>>> A couple of weeks ago, a discussion has started after Pierre's 
>>>>>> proposal for
>>>>>> a new syscall to change an ipc id (see thread
>>>>>> http://lkml.org/lkml/2008/1/29/209).
>>>>>>
>>>>>>
>>>>>> Oren's suggestion was to force an object's id during its creation, 
>>>>>> rather
>>>>>> than 1. create it, 2. change its id.
>>>>>>
>>>>>> So here is an implementation of what Oren has suggested.
>>>>>>
>>>>>> 2 new files are defined under /proc/self:
>>>>>>   . next_ipcid --> next id to use for ipc object creation
>>>>>>   . next_pids --> next upid nr(s) to use for next task to be forked
>>>>>>                   (see patch #2 for more details).
>>>>> Generally looks good. One meta-comment, though:
>>>>>
>>>>> I wonder why you use separate files for separate resources, 
>>>> That would be needed in a situation wheere we don't care about next, 
>>>> say, ipc id to be created but we need a predefined pid. But I must admit 
>>>> I don't see any pratical application to it.
>>> exactly; why set the next-ipc value so far in advance ?  I think it's
>>> better (and less confusing) if we require that setting the next-id value
>>> be done right before the respective syscall.
>> And race with some other syscall caller? This will only work if the next-ipc-id
>> and the next-pid are on a task_struct. Are they (at least supposed to be such)?
> 
> yes. that's the first detail I looked for in the patch :)

OK :) I just remembered some talks about using last_pid for pid allocations
and just wanted to be sure.