[Boost-users] [Asio] io_service and queuing priority

I have a program that uses an io_service to queue and execute function calls sequentially within its own thread. Other threads call io_service::post to queue small tasks, but every so often a large task is posted to the io_service. In my case, this large task is time-sensitive and must take priority over all other tasks. Is there a way to push that large task to the front of the io_service's queue, so I can guarantee it gets completed as soon as possible? A simpler way of asking my question: is it possible to prioritize an io_service queue? How? -- Dylan