[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] /proc/xen/xenbus supports watch?
On Tue, 2005-09-13 at 10:42 +0100, Christian Limpach wrote: > On 9/9/05, Rusty Russell <rusty@xxxxxxxxxxxxxxx> wrote: > > On Thu, 2005-09-08 at 11:38 +0100, Christian Limpach wrote: > > > On 9/8/05, NAHieu <nahieu@xxxxxxxxx> wrote: > > > > Anybody (Christian?) could please tell me if we can get the support > > > > for registering watch with /proc/xen/xenbus? (..OK, I know that we > > > > will change it this /proc stuff to a device soon) > > > > > > > > So far we can only do read/write/rm. I really miss the xen watch > > > > feature. > > > > At the moment, the xenbus device is a simple hack which grabs the lock > > on all store communication on open, and drops it on close. It's not > > really a general mechanism for tools in domUs to communicate with the > > store. > > Could we reduce the time we hold the lock to from before we call > xb_write until both data->bytes_left and data->awaiting_reply are 0 > again? I think this would work except for transactions, how do you > feel about supporting multiple transactions per connection? Should we > at least extend the interface now so that we can add concurrent > transaction support later, i.e. transaction start returning a handle > and all operations taking a handle argument? I think if we want to do this we should actually introduce a new mechanism for communications. There's no reason why a domain can't introduce more pages for xenstore communication beyond the one it is given to start with, is there? (OK, unintroduce needs to take a shared page instead/as well as a domid). So when someone opens the xenbus dev, we introduce a new page to the domain and the xenstored uses that for comms. When closed, the page is released. This actually simplifies the xenbus_dev driver a lot: now it's just a dumb pass-through since we don't have to worry about the userspace program blowing chunks all over the kernel's comms mechanism. I'll hack something up and see what you think... Rusty. -- A bad analogy is like a leaky screwdriver -- Richard Braakman _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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