linux-kernel - Re: Documentation for CLONE

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Message-ID: <492C1FCB.1080405@openvz.org>
Date:	Tue, 25 Nov 2008 18:54:51 +0300
From:	Pavel Emelyanov <xemul@...nvz.org>
To:	mtk.manpages@...il.com
CC:	Kir Kolyshkin <kir@...nvz.org>, linux-man@...r.kernel.org,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: Documentation for CLONE_NEWPID

>>> +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
> 

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