RVM-1055 : Move assertion for cursor state in allocPages into the syn…

…chronized part.

The cursor state cannot be safely checked in an unsynchronized part because different parts of the assertion checking code might see different values.

MMTk/src/org/mmtk/utility/heap/MonotonePageResource.java

@@ -127,6 +127,10 @@ public int getAvailablePhysicalPages() {
   @Override
   @Inline
   protected Address allocPages(int reservedPages, int requiredPages, boolean zeroed) {
+    boolean newChunk = false;
+    lock();
+    Address rtn = cursor;
+
     if (VM.VERIFY_ASSERTIONS) {
       /*
        * Cursor should always be zero, or somewhere in the current chunk.  If we have just
@@ -141,9 +145,6 @@ protected Address allocPages(int reservedPages, int requiredPages, boolean zeroe
           Space.chunkAlign(cursor, true).EQ(currentChunk) ||
           Space.chunkAlign(cursor, true).EQ(currentChunk.plus(Space.BYTES_IN_CHUNK)));
     }
-    boolean newChunk = false;
-    lock();
-    Address rtn = cursor;
 
     if (metaDataPagesPerRegion != 0) {
       /* adjust allocation for metadata */