Re: [Xen-devel] mapped memory delay?

[Christopher Clark <christopher.w.clark@xxxxxxxxx>]

Are you running this on a single processor core?

If not, it sounds to me like a cache coherency issue - you'll need a
write memory barrier after writing to the req_prod.  If you're using
the ring macros from io/ring.h this should be already taken care of
for you in the push macros.

c.


On Fri, 18 Feb 2005 16:44:30 -0500 (EST), Xin Zhao
<zhaoxin@xxxxxxxxxxxxxx> wrote:
> I ran into the following problem:
> 
> I setup a shared ring page and an event channel between two domains (dom0
> and one domU), DomU increases req_prod by one and notify the dom0 via the
> event channel, dom0 then check req_prod pointer and process the request in
> the shared ring. But I noticed that sometimes dom0 get the irq triggered
> by the notification event, but the req_prod remains the same. This
> situation only happened occasionally. Why? Because the req_prod is saved
> in the shared, mapped page, I suspect that there is a delay of updates
> between two domains. Is that true? If so, how to handle this problem?
> 
> Your advice is highly appreciated!
> 
> -x
> 
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