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 12:05:24 +0100
Message-ID: <20110218110524.GA10012@aepfle.de>
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To: James Harper <james.harper@bendigoit.com.au>
Cc: xen-devel@lists.xensource.com, Ian Jackson <Ian.Jackson@eu.citrix.com>
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On Fri, Feb 18, James Harper wrote:

> I think I have found the error and it was probably a 1 in a million race
> so stress testing might not have helped anyway. My code went:
> 
> len = min(ring->rsp_prod - ring->rsp_cons, msg_size)
> 
> and the ASSERT was hit because len was > msg_size, and the only possible
> way I can ever see that happening is if ring->rsp_prod changed between
> the if in the min() and the assignment. I'm now snapshotting rsp_prod to
> a local variable at the start. Kind of embarrassing really as plenty of
> example code exists.

Why is there no lock to protect the ring accesses?

Olaf