Re: [Xen-devel] [Minios-devel] [PATCH MINI-OS v2] xenbus: notify the other end when necessary

[Samuel Thibault <samuel.thibault@xxxxxxxxxxxx>]

Wei Liu, le Mon 26 Oct 2015 13:55:31 +0000, a écrit :
> On Mon, Oct 26, 2015 at 01:52:47PM +0100, Samuel Thibault wrote:
> > Wei Liu, le Mon 26 Oct 2015 12:47:56 +0000, a écrit :
> > > -            if (xenstore_buf->rsp_prod - xenstore_buf->rsp_cons < 
> > > sizeof(msg))
> > > +            if (xenstore_buf->rsp_prod - xenstore_buf->rsp_cons < 
> > > sizeof(msg)) {
> > > +                notify_remote_via_evtchn(start_info.store_evtchn);
> > >                  break;
> > > +            }
> > 
> > >              if (xenstore_buf->rsp_prod - xenstore_buf->rsp_cons <
> > > -                    sizeof(msg) + msg.len)
> > > +                    sizeof(msg) + msg.len) {
> > > +                notify_remote_via_evtchn(start_info.store_evtchn);
> > 
> > Actually thinking...  In principle we should not need these two
> > notifications: we have already notified last time we consumed a message.
> > Notifying again shouldn't be bringing anything new.  Do you actually see
> > a difference with these?
> > 
> 
> Yes. The ring still gets stalled somehow without those two
> notifications.

Ok...  This is still very worrying.  The more I'm thinking about it,
the more I believe we shouldn't *have* to do this.  Which version of
the xenstore are you testing with, exactly?  I guess that while we
investigate this oddness we can apply this fix to stable trees, so as to
be safer than sorry.

Samuel

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