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

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

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)?