From mboxrd@z Thu Jan  1 00:00:00 1970
From: =?ISO-8859-1?Q?Roger_Pau_Monn=E9?= <roger.pau@citrix.com>
Subject: Re: RING_HAS_UNCONSUMED_REQUESTS oddness
Date: Wed, 12 Mar 2014 11:48:29 +0100
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To: Ian Campbell <Ian.Campbell@citrix.com>, Zoltan Kiss <zoltan.kiss@citrix.com>
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On 12/03/14 11:28, Ian Campbell wrote:
> On Tue, 2014-03-11 at 23:24 +0000, Zoltan Kiss wrote:
>> On 11/03/14 15:44, Ian Campbell wrote:
> 
>>> Is it the case that this macro considers a request to be unconsumed if
>>> the *response* to a request is outstanding as well as if the request
>>> itself is still on the ring?
>> I don't think that would make sense. I think everywhere where this macro 
>> is called the caller is not interested in pending request (pending means 
>> consumed but not responded)
> 
> It might be interested in such pending requests in some of the
> pathological cases I allude to in the next paragraph though?
> 
> For example if the ring has unconsumed requests but there are no slots
> free for a response, it would be better to treat it as no unconsumed
> requests until space opens up for a response, otherwise something else
> just has to abort the processing of the request when it notices the lack
> of space.

Yes, I think this is true at least for blkback, when blkback starts
processing a request it assumes that a response slot will be available
in order to write the response when the request has finished processing.

Roger.