[boost] [asio] global timer cancellation?

Hi, I've got various objects that make use of the asio deadline timer to schedule events. The problem is that there isn't a central repository of timer references that I can walk to cancel them when shutting down asio. I'd like to be able to just tell asio to cancel any pending work and have the thread(s) return. Is this possible? I came across the io_service::work class but haven't yet found an example of how it works. Thanks, Brian