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RE: [Xen-devel] A bug in Xenbus driver

To: Jeremy Fitzhardinge <jeremy@xxxxxxxx>
Subject: RE: [Xen-devel] A bug in Xenbus driver
From: "Jun Zhu (Intern)" <Jun.Zhu@xxxxxxxxxx>
Date: Thu, 26 Aug 2010 09:25:30 +0100
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Thread-topic: [Xen-devel] A bug in Xenbus driver

Sorry for my description. "Does not report correctly" is not the problem of 
xenbus read. 
I mean that in the xenstore/xs.c code, when using another thread (#ifdef 
USE_PTHREAD) to receive responses from xenbus, if this thread exits 
incorrectly, the listener should be noticed, or the listener will wait for 
response for ever.  

Jun Zhu
Citrix Systems UK

From: Jeremy Fitzhardinge [jeremy@xxxxxxxx]
Sent: Wednesday, August 25, 2010 3:19 PM
To: Jun Zhu (Intern)
Cc: xen-devel@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Xen-devel] A bug in Xenbus driver

 On 08/25/2010 11:57 AM, Jun Zhu (Intern) wrote:
> This bug makes the read_buffer not be cleared most of the time. If the 
> xenstore client uses PTHREAD to create a thread to receive reply message, the 
> problem will incur. The new thread can not read what it wants to read, since 
> the list is not empty.

This still puzzles me.  The bug you found means that
partially-successful reads will not be reported correctly, but
completely successful and completely unsuccessful reads should be OK.
So if you're seeing a problem as a result, it still indicates there's
something wrong with what you're passing to read().


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