8319251: [REDO] Change LockingMode default from LM_LEGACY to LM_LIGHTWEIGHT

Reviewed-by: rkennke, dholmes

Author: Daniel D. Daugherty

src/hotspot/share/runtime/globals.hpp

@@ -1969,11 +1969,11 @@ const int ObjectAlignmentInBytes = 8;
              "Mark all threads after a safepoint, and clear on a modify "   \
              "fence. Add cleanliness checks.")                              \
                                                                             \
-  product(int, LockingMode, LM_LEGACY,                                      \
+  product(int, LockingMode, LM_LIGHTWEIGHT,                                 \
           "Select locking mode: "                                           \
           "0: monitors only (LM_MONITOR), "                                 \
-          "1: monitors & legacy stack-locking (LM_LEGACY, default), "       \
-          "2: monitors & new lightweight locking (LM_LIGHTWEIGHT)")         \
+          "1: monitors & legacy stack-locking (LM_LEGACY), "                \
+          "2: monitors & new lightweight locking (LM_LIGHTWEIGHT, default)") \
           range(0, 2)                                                       \
                                                                             \
   product(uint, TrimNativeHeapInterval, 0,                                  \

test/jtreg-ext/requires/VMProps.java

@@ -419,13 +419,15 @@ protected String vmHasDTrace() {
     }
 
     /**
-     * @return true if compiler in use supports RTM and false otherwise.
+     * @return "true" if compiler in use supports RTM and "false" otherwise.
+     * Note: Lightweight locking does not support RTM (for now).
      */
     protected String vmRTMCompiler() {
         boolean isRTMCompiler = false;
 
         if (Compiler.isC2Enabled() &&
-            (Platform.isX86() || Platform.isX64() || Platform.isPPC())) {
+            (Platform.isX86() || Platform.isX64() || Platform.isPPC()) &&
+            is_LM_LIGHTWEIGHT().equals("false")) {
             isRTMCompiler = true;
         }
         return "" + isRTMCompiler;
@@ -481,6 +483,34 @@ protected String vmPageSize() {
         return "" + WB.getVMPageSize();
     }
 
+    /**
+     * @return LockingMode.
+     */
+    protected String vmLockingMode() {
+        return "" + WB.getIntVMFlag("LockingMode");
+    }
+
+    /**
+     * @return "true" if LockingMode == 0 (LM_MONITOR)
+     */
+    protected String is_LM_MONITOR() {
+        return "" + vmLockingMode().equals("0");
+    }
+
+    /**
+     * @return "true" if LockingMode == 1 (LM_LEGACY)
+     */
+    protected String is_LM_LEGACY() {
+        return "" + vmLockingMode().equals("1");
+    }
+
+    /**
+     * @return "true" if LockingMode == 2 (LM_LIGHTWEIGHT)
+     */
+    protected String is_LM_LIGHTWEIGHT() {
+        return "" + vmLockingMode().equals("2");
+    }
+
     /**
      * Check if Graal is used as JIT compiler.
      *