Comment by pron
6 days ago
Nice post!
A minor point:
> monitors are incompatible with coroutines
If by coroutines the author meant virtual threads, then monitors have always been compatible with virtual threads (which have always needed to adhere to the Thread specification). Monitors could, for a short while, degrade the scalability of virtual threads (and in some situations even lead to deadlocks), but that has since been resolved in JDK 24 (https://openjdk.org/jeps/491).
I think it's coroutines as in other JVM languages like Kotlin, where yielding may be implemented internally as return (due to lack of native coroutine support in JVM).
Holding a lock/monitor across a yield is a bad idea for other reasons, so it shouldn't be a big deal in practice.
I meant polyfilled coroutines used by other JVM languages, like Kotlin. When you compile a coroutine to a state machine, yielding has to return from the machine; but JVM does not support unbalanced monitors, although it obviously does support unbalanced locking operations with normal mutexes.