Re: [Xen-devel] [PATCH MINI-OS] xenbus: notify the other end when necessary

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2015-11-02 at 15:00 +0000, Wei Liu wrote:
> On Mon, Nov 02, 2015 at 12:14:50PM +0000, Ian Campbell wrote:
> > On Mon, 2015-10-26 at 09:47 +0000, Wei Liu wrote:
> > > The xenbus thread didn't send notification to other end when it
> > > expected
> > > more data or consumed responses, which led to stalling the ring from
> > > time to time.
> > > 
> > > This is the culprit that guest was less responsive when using stubdom
> > > because the device model was stalled.
> > > 
> > > Fix this by sending notification to the other end at the right
> > > places.
> > 
> > Could any of this code benefit from using the various macros in ring.h
> > which produce or consume entries on the ring and return a _notify bit?
> > 
> 
> The bug is it doesn't send notification at all. The existing code in
> Linux doesn't seem to care about mitigating notifications -- xenbus is
> supposed to exchange small amount of information anyway so whether a few
> more notifications are sent is not essential. I think it would be better
> if we follow something that works at this stage.
> 
> The use of ring macro can be considered an improvement but not
> essential to fix the bug. It can be considered as improvement in the
> future.

My reason for suggesting it was more that we trust that those macros are
already correct, compared with needing to reason from scratch about the
open coded version used in this code which is what appeared to be going on.

Ian.

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