Fix bug which could generate deadlocks when multiple connections accessed the same table.

h2/src/docsrc/html/changelog.html

@@ -35,6 +35,7 @@ Change Log
 </li><li>Issue 581: When running in LOCK_MODE=0,
         JdbcDatabaseMetaData#supportsTransactionIsolationLevel(TRANSACTION_READ_UNCOMMITTED)
     should return false
+</li><li>Fix bug which could generate deadlocks when multiple connections accessed the same table.    
 </li></ul>
 
 <h2>Version 1.4.182 Beta (2014-10-17)</h2>

h2/src/main/org/h2/mvstore/db/MVTable.java

@@ -117,6 +117,9 @@ public class MVTable extends TableBase {
             return true;
         }
         synchronized (getLockSyncObject()) {
+            if (!exclusive && lockSharedSessions.contains(session)) {
+                return true;
+            }
             session.setWaitForLock(this, Thread.currentThread());
             waitingSessions.addLast(session);
             try {

h2/src/main/org/h2/table/RegularTable.java

@@ -463,6 +463,9 @@ public class RegularTable extends TableBase {
             if (lockExclusiveSession == session) {
                 return true;
             }
+            if (!exclusive && lockSharedSessions.contains(session)) {
+                return true;
+            }
             session.setWaitForLock(this, Thread.currentThread());
             waitingSessions.addLast(session);
             try {