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java.lang.Object
   |
   +----utah.npm.core.Debuggable
           |
           +----utah.npm.core.Lock

Summary

class  Lock
     extends utah.npm.core.Debuggable
{
          // Fields 2
     private boolean locked_;
     private Thread owner_;

          // Constructors 1
     public Lock();

          // Methods 7
     public void assertLocked();
     public void assertUnlocked();
     public boolean isLocked();
     public synchronized void lock();
     public native String toString();
     public synchronized boolean trylock();
     public synchronized void unlock();
}

Implment a "kernel"-internal mutex object. Through the magic of a pre-processor there are two versions of this class. The optimized version is entirely implemented with native methods, the unoptimized version is implemented entirely in Java.

Version:

NPMJava 0.5.0 April, 1998

Author:

Patrick Tullmann tullmann@cs.utah.edu

Fields

· locked_

Summary  |  Top

   private boolean locked_

Flag if the lock is locked or not.

   private Thread owner_

Record the owning thread of this lock. This is used for debugging (to make sure a thread does not try to lock a lock it owns, and will be used for CPU Inheritance Scheduling.

Constructors

· Lock

Summary  |  Top

   public Lock() 

   public boolean isLocked() 

Return true if this lock is already held.

Returns:

true if the lock is held, false if not.

See Also: trylock

   public void assertLocked() 

Assert that this lock is locked.

   public void assertUnlocked() 

Assert that the current thread doesn't own this lock. (Some other thread certainly might, and that's just peachy.)

Calls panic() if the lock is already held by the current thread.

   public synchronized void lock() 

Acquire this lock.

   public synchronized void unlock() 

Release this lock. The current thread must own the lock.

   public synchronized boolean trylock() 

Try to acquire this lock. The current thread should not already own this lock.

Returns:

true if the lock was acquired, false if it is already owned.

   public native String toString() 

Convert this lock to a string representation. This is native because we want to avoid dependencies on java.lang.* classes that may not be loaded into the space. (Specifically: java.lang.Integer, java.lang.Double, etc. for printing the name of the owner thread and the hash code.)

Overrides:

toString in class Object

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