From mboxrd@z Thu Jan  1 00:00:00 1970
From: Olaf Hering <olaf@aepfle.de>
Subject: Re: xenbus stress testing
Date: Fri, 18 Feb 2011 13:01:10 +0100
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To: Paul Durrant <Paul.Durrant@citrix.com>
Cc: James Harper <james.harper@bendigoit.com.au>, Ian Jackson <Ian.Jackson@eu.citrix.com>, "xen-devel@lists.xensource.com" <xen-devel@lists.xensource.com>
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On Fri, Feb 18, Paul Durrant wrote:

> How do you propose to lock against another VM updating a counter in shared memory?

I thought xenstore uses the same ringbuffer as defined by
DEFINE_RING_TYPES(). But reading the code in
include/xen/interface/io/xs_wire.h shows it has its own logic.

And reading further in xenpaging code, which I had in mind while I wrote
the mail, shows there is a separate spinlock.

I can imagine that even if a lock exists, a VM crashing while holding
the lock can stall all other VMs. So its probably not the best idea.

Olaf