Race condition between post and unsubscribe

[Brady Hahn]

In multi-threaded applications, it's currently possible for calls to unsubscribe to complete while event dispatch is ongoing. This could end up being problematic, such an example could be a cleanup routine that runs immediately after unsubscribe and invalidates objects referenced by an event callback. In these situations, a synchronous ListenerList implementation would be necessary, implemented using either a mutex or read-write lock depending on the setup.

Currently, all ListenerList usages are backed by CopyOnWriteListenerList, which is hard-coded into EventManager.

Extensibility

• Configurable ListenerList implementation via EventBusBuilder

ListenerList

• Single-threaded implementation
• Mutex wrapper
• Read-write lock wrapper