Date: Fri, 17 Mar 2006 02:11:55 +0100 (MET)
From: "Michael Kerrisk" <mtk-manpages@gmx.net>
To: Linus Torvalds <torvalds@osdl.org>
Cc: akpm@osdl.org, ebiederm@xmission.com, linux-kernel@vger.kernel.org,
       janak@us.ibm.com, viro@ftp.linux.org.uk, hch@lst.de, ak@muc.de,
       paulus@samba.org
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Subject: =?ISO-8859-1?Q?Re:_[PATCH]_unshare:_Cleanup_up_the_sys=5Funshare_interfac?=
 =?ISO-8859-1?Q?e_before_we_are_committed.?=
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Linus,

> On Fri, 17 Mar 2006, Michael Kerrisk wrote:
> > > 
> > > My personal opinion is that having a different set of flags is more 
> > > confusing 
> > 
> > How is it confusing?  And who is it confusing for?
> 
> It's confusing because
>  - it's just more flags to keep track of

Agreed, there is a "confusion cost" to that.

>  - it's all the same issues that clone() has

At the moment, but possibly not in the future (if one day
usnhare() needs a flag that has no analogue in clone()).

>  - it's an opportunity for future incoherence

Not sure what future incoherence you mean here.  Anyway,
we inject some incoherence *now* (some unshare() flags reverse
their clone() counterparts, one does not).

> > It will potentially require kernel developers to think for just 
> > a moment about what is going on.  But why care about them -- 
> > they don't have to *use* this interface; userland programmers do.
> 
> All the confusion is equally a userland issue, don't try to just enforce 
> your own opinions as somehow being "facts" by repeating them over 
> and over again.

I'm not trying to do that.  I've repeated my statements 
because I haven't seen any clear counterarguments.  I have a
particular opinion about what constitutes confusion, and it
comes from a perspective that focuses on the kernel-userland 
interface.  I agree that it does create some "confusion cost"
for userland programmers to add new flags.  But _in my opinion_
that cost is outweighed by the greater "confusion costs" that
I have described.  Eric seemed to agree.  Unfortunately for my
argument, you and Janak don't ;-).

Cheers,

Michael

-- 
Michael Kerrisk
maintainer of Linux man pages Sections 2, 3, 4, 5, and 7 

Want to help with man page maintenance?  
Grab the latest tarball at
ftp://ftp.win.tue.nl/pub/linux-local/manpages/, 
read the HOWTOHELP file and grep the source 
files for 'FIXME'.
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