[351793] Enhance LockMgr with write options

https://bugs.eclipse.org/bugs/show_bug.cgi?id=351793

1 files changed, 20 insertions, 1 deletions

diff --git a/plugins/org.eclipse.net4j.util/src/org/eclipse/net4j/util/concurrent/RWOLockManager.java b/plugins/org.eclipse.net4j.util/src/org/eclipse/net4j/util/concurrent/RWOLockManager.java
index 48a8643252..d61dd27ee2 100644
--- a/plugins/org.eclipse.net4j.util/src/org/eclipse/net4j/util/concurrent/RWOLockManager.java
+++ b/plugins/org.eclipse.net4j.util/src/org/eclipse/net4j/util/concurrent/RWOLockManager.java
@@ -26,6 +26,10 @@ import java.util.Map;
 import java.util.Set;
 
 /**
+ * Keeps track of locks on objects. Locks are owned by contexts. A particular combination of locks and their owners, for
+ * a given object, is represented by instances of the {@link LockState} class. This class is also repsonsible for
+ * deciding whether or not a new lock can be granted, based on the locks already present.
+ * 
  * @author Caspar De Groot
  * @since 3.2
  */
@@ -284,7 +288,17 @@ public class RWOLockManager<OBJECT, CONTEXT> extends Lifecycle implements IRWLoc
   }
 
   /**
-   * Represents a combination of locks for one OBJECT.
+   * Represents a combination of locks for one OBJECT. The different lock types are represented by the values of the
+   * enum {@link LockType}.
+   * <p>
+   * The locking semantics established by this class are as follows:
+   * <li>a read lock prevents a write lock by another, but allows read locks by others and allows a write option by
+   * another, and is therefore <b>non-exclusive</b></li>
+   * <li>a write lock prevents read locks by others, a write lock by another, and a write option by another, and is
+   * therefore <b>exclusive</b></li>
+   * <li>a write option prevents write locks by others and a write option by another, but allows read locks by others,
+   * and is therefore <b>exclusive</b></li>
+   * <p>
    * 
    * @author Caspar De Groot
    * @since 3.2
@@ -561,6 +575,11 @@ public class RWOLockManager<OBJECT, CONTEXT> extends Lifecycle implements IRWLoc
         return false;
       }
 
+      if (writeLockOwner != null && writeLockOwner != context)
+      {
+        return false;
+      }
+
       return true;
     }