src/java.base/share/classes/java/util/concurrent/ForkJoinPool.java

@@ -1280,11 +1280,10 @@
           */
          final void push(ForkJoinTask<?> task, ForkJoinPool pool, boolean internal) {
              int s = top, b = base, m, cap, room; ForkJoinTask<?>[] a;
              if ((a = array) != null && (cap = a.length) > 0 && // else disabled
                  task != null) {
-                 int pk = task.noUserHelp() + 1;             // prev slot offset
                  if ((room = (m = cap - 1) - (s - b)) >= 0) {
                      top = s + 1;
                      long pos = slotOffset(m & s);
                      if (!internal)
                          U.putReference(a, pos, task);       // inside lock

@@ -1295,12 +1294,13 @@
                  }
                  if (!internal)
                      unlockPhase();
                  if (room < 0)
                      throw new RejectedExecutionException("Queue capacity exceeded");
-                 if ((room == 0 || a[m & (s - pk)] == null) &&
-                     pool != null)
+                 if (pool != null &&
+                     (room == 0 ||
+                      U.getReferenceVolatile(a, slotOffset(m & (s - 1))) == null))
                      pool.signalWork();   // may have appeared empty
              }
          }
  
          /**