8214427: probable bug in logic of ConcurrentHashMap.addCount()

Reviewed-by: martin
Backport-of: 8846159

Author: gnu-andrew

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

@@ -2334,17 +2334,15 @@ private final void addCount(long x, int check) {
             Node<K,V>[] tab, nt; int n, sc;
             while (s >= (long)(sc = sizeCtl) && (tab = table) != null &&
                    (n = tab.length) < MAXIMUM_CAPACITY) {
-                int rs = resizeStamp(n);
+                int rs = resizeStamp(n) << RESIZE_STAMP_SHIFT;
                 if (sc < 0) {
-                    if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||
-                        sc == rs + MAX_RESIZERS || (nt = nextTable) == null ||
-                        transferIndex <= 0)
+                    if (sc == rs + MAX_RESIZERS || sc == rs + 1 ||
+                        (nt = nextTable) == null || transferIndex <= 0)
                         break;
                     if (U.compareAndSetInt(this, SIZECTL, sc, sc + 1))
                         transfer(tab, nt);
                 }
-                else if (U.compareAndSetInt(this, SIZECTL, sc,
-                                             (rs << RESIZE_STAMP_SHIFT) + 2))
+                else if (U.compareAndSetInt(this, SIZECTL, sc, rs + 2))
                     transfer(tab, null);
                 s = sumCount();
             }
@@ -2358,11 +2356,11 @@ final Node<K,V>[] helpTransfer(Node<K,V>[] tab, Node<K,V> f) {
         Node<K,V>[] nextTab; int sc;
         if (tab != null && (f instanceof ForwardingNode) &&
             (nextTab = ((ForwardingNode<K,V>)f).nextTable) != null) {
-            int rs = resizeStamp(tab.length);
+            int rs = resizeStamp(tab.length) << RESIZE_STAMP_SHIFT;
             while (nextTab == nextTable && table == tab &&
                    (sc = sizeCtl) < 0) {
-                if ((sc >>> RESIZE_STAMP_SHIFT) != rs || sc == rs + 1 ||
-                    sc == rs + MAX_RESIZERS || transferIndex <= 0)
+                if (sc == rs + MAX_RESIZERS || sc == rs + 1 ||
+                    transferIndex <= 0)
                     break;
                 if (U.compareAndSetInt(this, SIZECTL, sc, sc + 1)) {
                     transfer(tab, nextTab);