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Date: Fri, 6 Nov 2009 10:54:07 +0000
From: Jamie Lokier <jamie@shareable.org>
Subject: Re: [Qemu-devel] [PATCH 0/4] net-bridge: rootless bridge support for
	qemu
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To: Avi Kivity <avi@redhat.com>
Cc: Mark McLoughlin <markmc@redhat.com>, Anthony Liguori <aliguori@us.ibm.com>, Arnd Bergmann <arndbergmann@googlemail.com>, Arnd Bergmann <arnd@arndb.de>, Juan Quintela <quintela@redhat.com>, Dustin Kirkland <kirkland@canonical.com>, qemu-devel@nongnu.org, Michael Tsirkin <mst@redhat.com>

Avi Kivity wrote:
> >I know this has been discussed before, but isn't this why there are 
> >things like vfork()? 
> 
> vfork() doesn't work with threads - it requires that the calling process 
> be halted until exec() is called.

On Linux (NPTL), vfork() is good for this.  It only halts the calling
thread.  Other threads continue to run, and when the vfork'd thread
called exec*(), it doesn't affect the other threads.  Of course this
behaviour isn't portable, but then again, neither is KVM.

(Forget what I said elsewhere about Glibc using clone() to spawn
processes.  It's just Glibc's very complicated way of implementing
fork(), and doesn't share the parent's memory).

-- Jamie