From mboxrd@z Thu Jan  1 00:00:00 1970
From: "H. Peter Anvin" <hpa-YMNOUZJC4hwAvxtiuMwx3w@public.gmane.org>
Subject: Re: [PATCH 11/11][v15]: Document sys_eclone
Date: Sun, 04 Jul 2010 21:10:42 -0700
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To: Matt Helsley <matthltc-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>
Cc: Randy Dunlap <randy.dunlap-QHcLZuEGTsvQT0dZR+AlfA@public.gmane.org>, Serge Hallyn <serge.hallyn-Z7WLFzj8eWMS+FvcfC7Uqw@public.gmane.org>, Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>, Albert Cahalan <acahalan-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>, Containers <containers-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org>, Nathan Lynch <nathanl-V7BBcbaFuwjMbYB6QlFGEg@public.gmane.org>, Dan Smith <danms-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>, Sukadev Bhattiprolu <sukadev-23VcF4HTsmIX0ybBhKVfKdBPR1lH4CV8@public.gmane.org>, Roland McGrath <roland-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
List-Id: containers.vger.kernel.org

On 07/04/2010 04:39 PM, Matt Helsley wrote:
>>
>> 1. can you implement it for i386 (register starved) using eclone?
> 
> That's a very good question. I'm going to punt on a direct answer for
> now. Instead,  I wonder if it's even worth enabling vfork through eclone.
> vfork is rarely used, is supported by the "old" clone syscall, and any
> old code adapted to use eclone for vfork would need significant
> changes because of vfork's specialness. (A consequence of the way vfork
> borrows page tables and must avoid clobbering parent's registers..)
> 

vfork is its own system call for a reason.  We used to do it with
sys_clone, and it turned out to be a mess.  Doing it in a separate
system call -- even though the internals are largely the same -- is cleaner.

	-hpa
-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.