A synchronization mutex (mutual exclusion). A synchronization mutex (mutual exclusion). This is used to synchronize multiple [Thread]s, and is equivalent to a binary [Semaphore]. It guarantees that only one thread can ever acquire the lock at a time. A mutex can be used to protect a critical section; however, be careful to avoid deadlocks. It's of the recursive kind, so it can be locked multiple times by one thread, provided it also unlocks it as many times. [b]Warning:[/b] To guarantee that the operating system is able to perform proper cleanup (no crashes, no deadlocks), these conditions must be met: - By the time a [Mutex]'s reference count reaches zero and therefore it is destroyed, no threads (including the one on which the destruction will happen) must have it locked. - By the time a [Thread]'s reference count reaches zero and therefore it is destroyed, it must not have any mutex locked. $DOCS_URL/tutorials/performance/using_multiple_threads.html Locks this [Mutex], blocks until it is unlocked by the current owner. [b]Note:[/b] This function returns without blocking if the thread already has ownership of the mutex. Tries locking this [Mutex], but does not block. Returns [code]true[/code] on success, [code]false[/code] otherwise. [b]Note:[/b] This function returns [constant OK] if the thread already has ownership of the mutex. Unlocks this [Mutex], leaving it to other threads. [b]Note:[/b] If a thread called [method lock] or [method try_lock] multiple times while already having ownership of the mutex, it must also call [method unlock] the same number of times in order to unlock it correctly. [b]Warning:[/b] Calling [method unlock] more times that [method lock] on a given thread, thus ending up trying to unlock a non-locked mutex, is wrong and may causes crashes or deadlocks.