the key difference between posix draft 4 threads and the final posix threads specification, aside from a number of functions being interruptible where others are not, is thread cancellation. dce/rpc utilises thread cancellation to propagate signals across the "remote" of rpc, such that for example a client application terminating a thread results in its corresponding thread on the server also being terminated in the same way. unfortunately, the final posix specification does not include such sophisticated cancellation methodology, and, given the difficulties that the unix vendors had in correctly implementing the posix threads specification, it is not surprising that it was removed.