ISPN-993 Help to prevent deadlocks by making the lock id accessible t…

…hrough the public API

core/src/main/java/org/infinispan/util/concurrent/locks/LockManager.java

@@ -116,4 +116,18 @@ public interface LockManager {
     * @return an integer
     */
    int getNumberOfLocksHeld();
+
+   /**
+    * Returns the 'id' of the lock that will be used to guard access to a given key in the cache.  Particularly useful
+    * if Lock Striping is used and locks may guard more than one key.  This mechanism can be used to check whether
+    * keys may end up sharing the same lock.
+    * <p />
+    * If lock-striping is not used, the identity hash code of the lock created for this specific key is returned.  While
+    * this may not be of much value, it is done to maintain API compatibility of this method regardless of underlying
+    * locking scheme.
+    *
+    * @param key key to test for
+    * @return the ID of the lock.
+    */
+   int getLockId(Object key);
 }

core/src/main/java/org/infinispan/util/concurrent/locks/LockManagerImpl.java

@@ -47,9 +47,10 @@
 import javax.transaction.TransactionManager;
 import java.util.Iterator;
 import java.util.Map;
-import static java.util.concurrent.TimeUnit.MILLISECONDS;
 import java.util.concurrent.locks.Lock;
 
+import static java.util.concurrent.TimeUnit.MILLISECONDS;
+
 /**
  * Handles locks for the MVCC based LockingInterceptor
  *
@@ -203,4 +204,8 @@ public int getNumberOfLocksHeld() {
    public int getNumberOfLocksAvailable() {
       return lockContainer.size() - lockContainer.getNumLocksHeld();
    }
+
+   public int getLockId(Object key) {
+      return lockContainer.getLockId(key);
+   }
 }

core/src/main/java/org/infinispan/util/concurrent/locks/containers/AbstractPerEntryLockContainer.java

@@ -97,4 +97,8 @@ public void releaseLock(Object key) {
       Lock l = locks.remove(key);
       if (l != null) l.unlock();
    }
+
+   public int getLockId(Object key) {
+      return System.identityHashCode(getLock(key));
+   }
 }

core/src/main/java/org/infinispan/util/concurrent/locks/containers/AbstractStripedLockContainer.java

@@ -23,13 +23,12 @@
 package org.infinispan.util.concurrent.locks.containers;
 
 import net.jcip.annotations.ThreadSafe;
+import org.infinispan.util.logging.Log;
+import org.infinispan.util.logging.LogFactory;
 
 import java.util.concurrent.TimeUnit;
 import java.util.concurrent.locks.Lock;
 
-import org.infinispan.util.logging.Log;
-import org.infinispan.util.logging.LogFactory;
-
 import static org.infinispan.util.Util.safeRelease;
 
 /**
@@ -110,4 +109,8 @@ public void releaseLock(Object key) {
          log.debug("Attempted to unlock a lock we didn't own - swallowing an IllegalMonitorStateException");
       }
    }
+
+   public int getLockId(Object key) {
+      return hashToIndex(key);
+   }
 }

core/src/main/java/org/infinispan/util/concurrent/locks/containers/LockContainer.java

@@ -81,4 +81,18 @@ public interface LockContainer {
     * @param key Object on which lock is to be removed  
     */
    void releaseLock(Object key);
+
+   /**
+    * Returns the 'id' of the lock that will be used to guard access to a given key in the cache.  Particularly useful
+    * if Lock Striping is used and locks may guard more than one key.  This mechanism can be used to check whether
+    * keys may end up sharing the same lock.
+    * <p />
+    * If lock-striping is not used, the identity hash code of the lock created for this specific key is returned.  While
+    * this may not be of much value, it is done to maintain API compatibility of this method regardless of underlying
+    * locking scheme.
+    *
+    * @param key key to test for
+    * @return the ID of the lock.
+    */
+   int getLockId(Object key);
 }