From some other StackOverflow answers, seems mutex is needed if you need to guard a property or function from concurrent coroutine execution. However, I happened to look at the source code of StateFlow.kt today and noticed:
This property is thread-safe and can be safely updated from concurrent coroutines without external synchronization.
Looking further into the implementation, all it has are a few traditional synchronized blocks without mutexes.
So the question is, does @Synchronized or synchronized keyword(s) work on Kotlin coroutines? The forum discussions mostly indicate they do not, but the official StateFlow implementation suggests otherwise.
They work, but Mutex's should be preferred because they can suspend, which avoids blocking a thread the way synchronized would.
To make something truly thread-safe, such as StateFlow's value property, which can be set from any thread inside or outside of a coroutine, traditional synchronization is required.