AbstractQueuedLongSynchronizer

AbstractQueuedLongSynchronizer

protected AbstractQueuedLongSynchronizer()

Constructor for subclasses to call.

acquire

fun acquire(arg: Long): Unit

Acquires in exclusive mode, ignoring interrupts. Implemented by invoking at least once tryAcquire, returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquire until success. This method can be used to implement method Lock#lock.

acquireInterruptibly

fun acquireInterruptibly(arg: Long): Unit

Acquires in exclusive mode, aborting if interrupted. Implemented by first checking interrupt status, then invoking at least once tryAcquire, returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquire until success or the thread is interrupted. This method can be used to implement method Lock#lockInterruptibly.

acquireShared

fun acquireShared(arg: Long): Unit

Acquires in shared mode, ignoring interrupts. Implemented by first invoking at least once tryAcquireShared, returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquireShared until success.

acquireSharedInterruptibly

fun acquireSharedInterruptibly(arg: Long): Unit

Acquires in shared mode, aborting if interrupted. Implemented by first checking interrupt status, then invoking at least once tryAcquireShared, returning on success. Otherwise the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquireShared until success or the thread is interrupted.

getExclusiveQueuedThreads

fun getExclusiveQueuedThreads(): MutableCollection<Thread!>!

Returns a collection containing threads that may be waiting to acquire in exclusive mode. This has the same properties as getQueuedThreads except that it only returns those threads waiting due to an exclusive acquire.

getFirstQueuedThread

fun getFirstQueuedThread(): Thread!

Returns the first (longest-waiting) thread in the queue, or null if no threads are currently queued.

In this implementation, this operation normally returns in constant time, but may iterate upon contention if other threads are concurrently modifying the queue.

getQueueLength

fun getQueueLength(): Int

Returns an estimate of the number of threads waiting to acquire. The value is only an estimate because the number of threads may change dynamically while this method traverses internal data structures. This method is designed for use in monitoring system state, not for synchronization control.

getQueuedThreads

fun getQueuedThreads(): MutableCollection<Thread!>!

Returns a collection containing threads that may be waiting to acquire. Because the actual set of threads may change dynamically while constructing this result, the returned collection is only a best-effort estimate. The elements of the returned collection are in no particular order. This method is designed to facilitate construction of subclasses that provide more extensive monitoring facilities.

getSharedQueuedThreads

fun getSharedQueuedThreads(): MutableCollection<Thread!>!

Returns a collection containing threads that may be waiting to acquire in shared mode. This has the same properties as getQueuedThreads except that it only returns those threads waiting due to a shared acquire.

getWaitQueueLength

fun getWaitQueueLength(condition: AbstractQueuedLongSynchronizer.ConditionObject!): Int

Returns an estimate of the number of threads waiting on the given condition associated with this synchronizer. Note that because timeouts and interrupts may occur at any time, the estimate serves only as an upper bound on the actual number of waiters. This method is designed for use in monitoring system state, not for synchronization control.

getWaitingThreads

fun getWaitingThreads(condition: AbstractQueuedLongSynchronizer.ConditionObject!): MutableCollection<Thread!>!

Returns a collection containing those threads that may be waiting on the given condition associated with this synchronizer. Because the actual set of threads may change dynamically while constructing this result, the returned collection is only a best-effort estimate. The elements of the returned collection are in no particular order.

hasContended

fun hasContended(): Boolean

Queries whether any threads have ever contended to acquire this synchronizer; that is, if an acquire method has ever blocked.

In this implementation, this operation returns in constant time.

hasQueuedPredecessors

fun hasQueuedPredecessors(): Boolean

Queries whether any threads have been waiting to acquire longer than the current thread.

An invocation of this method is equivalent to (but may be more efficient than):

<code>getFirstQueuedThread() != Thread.currentThread()
    &amp;&amp; hasQueuedThreads()</code>

Note that because cancellations due to interrupts and timeouts may occur at any time, a true return does not guarantee that some other thread will acquire before the current thread. Likewise, it is possible for another thread to win a race to enqueue after this method has returned false, due to the queue being empty.

This method is designed to be used by a fair synchronizer to avoid barging. Such a synchronizer's tryAcquire method should return false, and its tryAcquireShared method should return a negative value, if this method returns true (unless this is a reentrant acquire). For example, the tryAcquire method for a fair, reentrant, exclusive mode synchronizer might look like this:

<code>protected boolean tryAcquire(long arg) {
    if (isHeldExclusively()) {
      // A reentrant acquire; increment hold count
      return true;
    } else if (hasQueuedPredecessors()) {
      return false;
    } else {
      // try to acquire normally
    }
  }</code>

hasQueuedThreads

fun hasQueuedThreads(): Boolean

Queries whether any threads are waiting to acquire. Note that because cancellations due to interrupts and timeouts may occur at any time, a true return does not guarantee that any other thread will ever acquire.

hasWaiters

fun hasWaiters(condition: AbstractQueuedLongSynchronizer.ConditionObject!): Boolean

Queries whether any threads are waiting on the given condition associated with this synchronizer. Note that because timeouts and interrupts may occur at any time, a true return does not guarantee that a future signal will awaken any threads. This method is designed primarily for use in monitoring of the system state.

isQueued

fun isQueued(thread: Thread!): Boolean

Returns true if the given thread is currently queued.

This implementation traverses the queue to determine presence of the given thread.

owns

fun owns(condition: AbstractQueuedLongSynchronizer.ConditionObject!): Boolean

Queries whether the given ConditionObject uses this synchronizer as its lock.

release

fun release(arg: Long): Boolean

Releases in exclusive mode. Implemented by unblocking one or more threads if tryRelease returns true. This method can be used to implement method Lock#unlock.

releaseShared

fun releaseShared(arg: Long): Boolean

Releases in shared mode. Implemented by unblocking one or more threads if tryReleaseShared returns true.

toString

open fun toString(): String

Returns a string identifying this synchronizer, as well as its state. The state, in brackets, includes the String "State =" followed by the current value of getState, and either "nonempty" or "empty" depending on whether the queue is empty.

tryAcquireNanos

fun tryAcquireNanos(
    arg: Long, 
    nanosTimeout: Long
): Boolean

Attempts to acquire in exclusive mode, aborting if interrupted, and failing if the given timeout elapses. Implemented by first checking interrupt status, then invoking at least once tryAcquire, returning on success. Otherwise, the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquire until success or the thread is interrupted or the timeout elapses. This method can be used to implement method Lock#tryLock(long, TimeUnit).

tryAcquireSharedNanos

fun tryAcquireSharedNanos(
    arg: Long, 
    nanosTimeout: Long
): Boolean

Attempts to acquire in shared mode, aborting if interrupted, and failing if the given timeout elapses. Implemented by first checking interrupt status, then invoking at least once tryAcquireShared, returning on success. Otherwise, the thread is queued, possibly repeatedly blocking and unblocking, invoking tryAcquireShared until success or the thread is interrupted or the timeout elapses.

compareAndSetState

protected fun compareAndSetState(
    expect: Long, 
    update: Long
): Boolean

Atomically sets synchronization state to the given updated value if the current state value equals the expected value. This operation has memory semantics of a volatile read and write.

getState

protected fun getState(): Long

Returns the current value of synchronization state. This operation has memory semantics of a volatile read.

isHeldExclusively

protected open fun isHeldExclusively(): Boolean

Returns true if synchronization is held exclusively with respect to the current (calling) thread. This method is invoked upon each call to a ConditionObject method.

The default implementation throws UnsupportedOperationException. This method is invoked internally only within ConditionObject methods, so need not be defined if conditions are not used.

setState

protected fun setState(newState: Long): Unit

Sets the value of synchronization state. This operation has memory semantics of a volatile write.

tryAcquire

protected open fun tryAcquire(arg: Long): Boolean

Attempts to acquire in exclusive mode. This method should query if the state of the object permits it to be acquired in the exclusive mode, and if so to acquire it.

This method is always invoked by the thread performing acquire. If this method reports failure, the acquire method may queue the thread, if it is not already queued, until it is signalled by a release from some other thread. This can be used to implement method Lock#tryLock().

The default implementation throws UnsupportedOperationException.

tryAcquireShared

protected open fun tryAcquireShared(arg: Long): Long

Attempts to acquire in shared mode. This method should query if the state of the object permits it to be acquired in the shared mode, and if so to acquire it.

This method is always invoked by the thread performing acquire. If this method reports failure, the acquire method may queue the thread, if it is not already queued, until it is signalled by a release from some other thread.

The default implementation throws UnsupportedOperationException.

tryRelease

protected open fun tryRelease(arg: Long): Boolean

Attempts to set the state to reflect a release in exclusive mode.

This method is always invoked by the thread performing release.

The default implementation throws UnsupportedOperationException.

tryReleaseShared

protected open fun tryReleaseShared(arg: Long): Boolean

Attempts to set the state to reflect a release in shared mode.

This method is always invoked by the thread performing release.

The default implementation throws UnsupportedOperationException.