RFR FJ parallelism zero

[Chris Hegarty]

Source changes that follow Doug's mail on lambda-libs-spec-observers

http://mail.openjdk.java.net/pipermail/lambda-libs-spec-observers/2013-August/002361.html

These changes are already in the jsr166 CVS, and there is a test in 
OpenJDK that verifies the change.

diff --git a/src/share/classes/java/util/concurrent/ForkJoinPool.java 
b/src/share/classes/java/util/concurrent/ForkJoinPool.java
--- a/src/share/classes/java/util/concurrent/ForkJoinPool.java
+++ b/src/share/classes/java/util/concurrent/ForkJoinPool.java
@@ -144,7 +144,8 @@ import java.util.concurrent.TimeUnit;
   * Upon any error in establishing these settings, default parameters
   * are used. It is possible to disable or limit the use of threads in
   * the common pool by setting the parallelism property to zero, and/or
- * using a factory that may return {@code null}.
+ * using a factory that may return {@code null}. However doing so may
+ * cause unjoined tasks to never be executed.
   *
   * <p><b>Implementation notes</b>: This implementation restricts the
   * maximum number of running threads to 32767. Attempts to create
@@ -3303,8 +3304,8 @@ public class ForkJoinPool extends Abstra
          }

          if (parallelism < 0 && // default 1 less than #cores
-            (parallelism = Runtime.getRuntime().availableProcessors() - 
1) < 0)
-            parallelism = 0;
+            (parallelism = Runtime.getRuntime().availableProcessors() - 
1) <= 0)
+            parallelism = 1;
          if (parallelism > MAX_CAP)
              parallelism = MAX_CAP;
          return new ForkJoinPool(parallelism, factory, handler, LIFO_QUEUE,

-Chris.