Re: Documentation for CLONE_NEWPID

Pavel Emelyanov
2008-11-25T15:54:51Z

>>> +A PID namespace provides an isolated environment for PIDs:
>>> +PIDs in a new namespace start at 1,
>>> +somewhat like a standalone system, and calls to
>>> +.BR fork (2),
>>> +.BR vfork (2),
>>> +or
>>> +.BR clone (2)
>>> +will produce processes whose PIDs within the namespace
>>> +are only guaranteed to be unique within that namespace.
>> Well, I'm not sure I understood correctly what was meant here, but after
>
> I've simplified that sentence somewhat. Now it just reads:
>
> A PID namespace provides an isolated environment for
> PIDs: PIDs in a new namespace start at 1, somewhat like
> a standalone system, and calls to fork(2), vfork(2), or
> clone(2) will produce processes with PIDs that are
> unique within the namespace.

OK, thanks.

>> we have a namespace each task has two pids. And _all_ of them are unique
>> in corresponding namespaces.
>
> And I already make that point lower down in the text (see ***), but
> now I extended the sentence there a little.
>
> [...]
>
> *** Here's where I make the point about each process having multiple PIDs"
>
>>> +The existence of a namespace hierarchy means that each process
>>> +may now have multiple PIDs:
>>> +one for each namespace in which it is visible.
>
> I added some words here:
>
> "each of these PIDs is unique within the corresponding namespace".

Correct.

>>> +(A call to
>>> +.BR getpid (2)
>>> +always returns the PID associated with the namespace in which
>>> +the process was created.)
>> I don't thinks it's a good example - the getpid cannot be called
>> for other process other than current :)
>
> It wasn't meant as an example. The point was, with a process
> potentially being a member of multiple namespaces, the reader might
> wonder: what does getpid(2) return? This sentence was intended to
> clarify that. With that explanation, does this sentence now seem
> okay?

Yes, but I'd change "was created" into "lives in". From my POV this
sounds more clear. I do not insist however :)

> [...]
>
> Cheers,
>
> Michael