Re: [Xen-devel] xenbus stress testing

To:	James Harper <james.harper@xxxxxxxxxxxxxxxx>, Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>
Subject:	Re: [Xen-devel] xenbus stress testing
From:	Keir Fraser <keir@xxxxxxx>
Date:	Fri, 18 Feb 2011 13:08:30 +0000
Cc:	xen-devel@xxxxxxxxxxxxxxxxxxx
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On 18/02/2011 12:42, "James Harper" <james.harper@xxxxxxxxxxxxxxxx> wrote:

>> You need to think about memory barriers and/or volatile.  Simply
>> "snapshotting" with an ordinary assignment doesn't work.
>> 
>> I don't know how this is done in Windows but the Linux kernel has a
>> clear explanation of the problem and how it's solved in Linux.  Look
>> in the kernel source tree in Documentation/memory-barriers.txt.
>> 
> 
> I issue a barrier (KeMemoryBarrier() which is a compiler and a memory
> barrier) after copying rsp_prod, eg:
> 
> rsp_prod = ring->rsp_prod;
> KeMemoryBarrier();
> Access the actual ring buffer
> 
> Is there anything else required?

Should be okay. That's basically what all other xenstore clients are doing.

 -- Keir



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Re: [Xen-devel] xenbus stress testing