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Diffstat (limited to 'java/JACE/Concurrency/Mutex.java')
| -rw-r--r-- | java/JACE/Concurrency/Mutex.java | 239 |
1 files changed, 0 insertions, 239 deletions
diff --git a/java/JACE/Concurrency/Mutex.java b/java/JACE/Concurrency/Mutex.java deleted file mode 100644 index 856fdbd79eb..00000000000 --- a/java/JACE/Concurrency/Mutex.java +++ /dev/null @@ -1,239 +0,0 @@ -/************************************************* - * - * = PACKAGE - * JACE.Concurrency - * - * = FILENAME - * Mutex.java - * - *@author Prashant Jain - *@author Everett Anderson - * - *************************************************/ -package JACE.Concurrency; - -import java.util.*; -import JACE.ASX.*; - -/** - * Value added abstraction for mutex variable creation. - * - * A mutex whose operations do not block forever and can time out. - * <P> - * <EM>This class does not support recursive semantics.</EM> - */ -public class Mutex extends LockAdapter -{ - /** - * Acquire ownership of the lock, blocking indefinitely if necessary. - * <P> - *@return AbstractLock.FAILURE or AbstractLock.SUCCESS - *@exception InterruptedException indicates another thread has - * interrupted this one during wait - */ - public synchronized int acquire () throws InterruptedException - { - if (this.monitor_.condition ()) { - this.monitor_.condition (false); - setOwner (); - return AbstractLock.SUCCESS; - } - - this.numberOfWaiters_++; - try { - sleepHook (); - this.monitor_.timedWait (); - } finally { - this.numberOfWaiters_--; - } - this.monitor_.condition (false); - setOwner(); - - return AbstractLock.SLEEPHOOK; - } - - public int renew (int requeuePosition, - TimeValue timeout) - throws InterruptedException, - TimeoutException - { - RenewObject rwo; - - synchronized (this) { - - if (!this.isOwner ()) - return AbstractLock.FAILURE; - - if (numberOfWaiters_ == 0 || requeuePosition == 0) - return AbstractLock.SUCCESS; - - if (requeuePosition < 0 || requeuePosition > numberOfWaiters_) - requeuePosition = numberOfWaiters_; - - rwo = new RenewObject (requeuePosition); - - this.release (); - this.renewers_.addElement (rwo); - } - - // We can't have the method synchronized, or synchronize on (this) - // in here because then the Thread that was woken up won't be able - // to continue its acquire. - // - // Normally when an exception occurs in timedWait, this thread just - // needs to remove itself from the renewers queue. - // - // However, the following situation exists: - // Thread A is the current owner, and is doing processing in release() - // This thread generates a timeout exception in timedWait - // Thread A signals this thread to wake up and take ownership, and - // removes it from the queue. - // This thread never takes ownership -- the exception keeps going up. - // - // This could lead to other renewers waiting in limbo forever. - // - // Solution: If this thread has an exception and it looks like it - // has been proclaimed the owner, then it calls release and lets - // the exception continue. - - boolean exceptionOccured = true; - try { - synchronized (rwo) { - rwo.timedWait (timeout); - - exceptionOccured = false; - } - } finally { - if (exceptionOccured) { - synchronized (this) { - if (!renewers_.removeElement (rwo)) { - setOwner (); - release (); - } - } - } - } - - synchronized (this) { - setOwner (); - } - - // By this point, we should know that we have the lock. The condition - // flag is never set to true in the release() call from the Thread - // that gave us control. - - return AbstractLock.SUCCESS; - } - - public synchronized int tryAcquire () { - if (this.monitor_.condition ()) { - this.monitor_.condition (false); - setOwner(); - return AbstractLock.SUCCESS; - } else - return AbstractLock.FAILURE; - } - - public synchronized int acquire (TimeValue tv) - throws TimeoutException, InterruptedException - { - if (this.monitor_.condition ()) { - this.monitor_.condition (false); - setOwner (); - return AbstractLock.SUCCESS; - } - - this.numberOfWaiters_++; - try { - sleepHook (); - this.monitor_.timedWait (tv); - } finally { - this.numberOfWaiters_--; - } - this.monitor_.condition (false); - setOwner(); - - return AbstractLock.SLEEPHOOK; - } - - /** - * Checks any objects in the renewers queue, giving one of them - * the lock if it is appropriate. Assumes the synchronization - * lock is already held. - * - *@return true if a renewer was signaled, else false - */ - protected boolean signalNextRenewer () - { - // First find the renewer with the minimum yieldTo count, processing - // all of them along the way. - if (this.renewers_.size() > 0) { - - RenewObject renewer = (RenewObject)renewers_. - elementAt (renewers_.size () - 1); - - renewer.decrementYieldTo (); - - for (int i = this.renewers_.size() - 2; i >=0; i--) { - - RenewObject rwo = (RenewObject)renewers_.elementAt (i); - - rwo.decrementYieldTo (); - - renewer = renewer.min (rwo); - } - - // If the renewer with the minimum yieldTo count has yielded to - // enough threads, or if there are no waiting threads, it should - // be signaled (thus, it wakes up and obtains the lock again). - - if (renewer.condition () || numberOfWaiters_ == 0) { - // Note that we leave monitor_.condition in the false state so - // we are assured that only the renewer (and not another - // Thread that does an acquire) will gain control. This - // is important since the renew method can't be synchronized - // in its current implementation. - renewers_.removeElement(renewer); - - synchronized (renewer) { - renewer.signal (); - } - - return true; - } - } - - return false; - } - - public synchronized int release () - { - if (!isOwner()) - return AbstractLock.FAILURE; - - if (!signalNextRenewer ()) { - // Do a normal release if there are no threads waiting to renew - // or no such threads are ready to renew. - this.monitor_.condition (true); - this.monitor_.signal (); - } - - return AbstractLock.SUCCESS; - } - - /** - * Monitor used to signal whether or not this Mutex is available. - */ - protected WaitObject monitor_ = new WaitObject (true, this); - // The monitor (adapter) to wait on - - /** - * Queue of waiting renewers. - */ - protected Vector renewers_ = new Vector (); - - /** - * Number of waiting threads. - */ - protected int numberOfWaiters_ = 0; -} |