4.2
Coordinate coroutines with synchronization primitives analogous to those the standard library provides to threads. These classes are very similar to those provided in the standard library's asyncio package.
Warning
Note that these primitives are not actually thread-safe and cannot be used in place of those from the standard library's threading module--they are meant to coordinate Tornado coroutines in a single-threaded app, not to protect shared objects in a multithreaded app.