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


Nadia Derbey wrote:
> Nick Andrew wrote:
>> On Fri, Apr 04, 2008 at 04:51:29PM +0200, Nadia.Derbey@bull.net wrote:
>>
>>> . echo "LONG XX" > /proc/self/next_id
>>> next object to be created will have an id set to XX
>>> . echo "LONG<n> X0 ... X<n-1>" > /proc/self/next_id
>>> next object to be created will have its ids set to XX0, ... X<n-1>
>>> This is particularly useful for processes that may have several
>>> ids if
>>> they belong to nested namespaces.
>>
>>
>> How do you handle race conditions, i.e. you specify the ID for the
>> next object to be created, and then some other thread goes and creates
>> an object before your thread creates one?
>>
>> Nick.
>
>
> Sorry for not answering earlier, I just saw your e-mail!

[I too managed to miss that message].

>
> It's true that the way I've done things, the "create_with_id" doesn't
> take into account multi-threaded apps, since "self" is related to the
> thread group leader.
>
> May be using something like /proc/self/task/<my_tid>/next_id would be
> better, but I have to think more about it...

That /proc/self links to /proc/TGID slipped my mind. Definitely must
be done on a per-thread basis (and /proc/<TGID>/task/<PID>/next_id
will do the trick).

Oren.

>
> Regards,
> Nadia


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