Yes, that's not well developed. However, it is the reason TS mutexes are shareable. If there is a resource shared between continuations the TS approach is to have those continuations share the same mutex leading to natural rescheduling for lock contention. In addition, that TS mutexes are recusive makes it so that if you can arrange for all of the continuations sharing a resource to be on the same ET_NET thread then locking is effectively cost free, yet remains robust in the cases where there is actual lock contention.
Because of the proxy (pass-through) nature of I/O in TS, it's quite difficult to keep shared resources on the same thread if outbound sessions are shared across threads. It is also problematic in the case of scheduling to and from different thread pools (although Fei's work should address to a large extent).
