interface Mutex (source)

Mutual exclusion for coroutines.

Mutex has two states: locked and unlocked. It is non-reentrant, that is invoking lock even from the same thread/coroutine that currently holds the lock still suspends the invoker.

JVM API note: Memory semantic of the Mutex is similar to synchronized block on JVM: An unlock on a Mutex happens-before every subsequent successful lock on that Mutex. Unsuccessful call to tryLock do not have any memory effects.



abstract val isLocked: Boolean

Returns true when this mutex is locked.


abstract val onLock: SelectClause2<Any?, Mutex>

Clause for select expression of lock suspending function that selects when the mutex is locked. Additional parameter for the clause in the owner (see lock) and when the clause is selected the reference to this mutex is passed into the corresponding block.



abstract fun holdsLock(owner: Any): Boolean

Checks mutex locked by owner


abstract suspend fun lock(owner: Any? = null): Unit

Locks this mutex, suspending caller while the mutex is locked.


abstract fun tryLock(owner: Any? = null): Boolean

Tries to lock this mutex, returning false if this mutex is already locked.


abstract fun unlock(owner: Any? = null): Unit

Unlocks this mutex. Throws IllegalStateException if invoked on a mutex that is not locked or was locked with a different owner token (by identity).

Extension Functions


suspend fun <T> Mutex.withLock(
    owner: Any? = null,
    action: () -> T
): T

Executes the given action under this mutex’s lock.