Re: [Xen-devel] [PATCH] cxenstored: correct calculation of data/space in the ring

[Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx>]

Andrew Cooper writes ("Re: [PATCH] cxenstored: correct calculation of 
data/space in the ring"):
> On 16/11/15 18:01, Ian Jackson wrote:
> > Wei Liu writes ("[PATCH] cxenstored: correct calculation of data/space in 
> > the ring"):
> >> The cxenstored implementation can't handle cross ring boundary read and
> >> write. It gets aways with buggy behaviour because upper layer won't
> >> sleep when short-write or short-read occurs.
> > I don't understand why you think this is a bug.
> 
> It is exactly the same bug as I fixed in c/s 8a2c11f8
> 
> The short reads/writes themselves aren't inherently a problem.  They are
> genuine signals that the server should wait for the client to
> produce/consume more data.
> 
> However, the low level functions erroneously return a short read/write
> when hitting the ring boundary when there is actually more space/data. 
> This causes a protocol stall as the server incorrectly believes that the
> client has the next action to perform.

If I understand Wei correctly you are contradicting him.  The `upper
layer' in question is inside the C xenstored so there is no protocol
stall.

(I haven't peered at the code...)

Ian.

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