RE: [Xen-devel] xenbus stress testing

["James Harper" <james.harper@xxxxxxxxxxxxxxxx>]

> 
> On Fri, Feb 18, Paul Durrant wrote:
> 
> > How do you propose to lock against another VM updating a counter in shared
> memory?
> 
> I thought xenstore uses the same ringbuffer as defined by
> DEFINE_RING_TYPES(). But reading the code in
> include/xen/interface/io/xs_wire.h shows it has its own logic.
> 
> And reading further in xenpaging code, which I had in mind while I wrote
> the mail, shows there is a separate spinlock.
> 
> I can imagine that even if a lock exists, a VM crashing while holding
> the lock can stall all other VMs. So its probably not the best idea.
> 

It's also inefficient when a perfectly good lock free method exists.

James

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