improve locking of class initialization

context.js

@@ -32,7 +32,6 @@ Context.prototype.popFrame = function() {
 Context.prototype.pushClassInitFrame = function(classInfo) {
   if (classInfo.initialized)
     return;
-  // console.log("starting initialization of", classInfo.className, this.thread.toString());
   classInfo.thread = this.thread;
   var syntheticMethod = {
     classInfo: {
@@ -53,8 +52,12 @@ Context.prototype.pushClassInitFrame = function(classInfo) {
     code: [
         0x2a,             // aload_0
         0x59,             // dup
+        0x59,             // dup
+        0x59,             // dup
+        0xc2,             // monitorenter
         0xb7, 0x00, 0x01, // invokespecial <idx=1>
         0xb7, 0x00, 0x07, // invokespecial <idx=7>
+        0xc3,             // monitorexit
         0xb1,             // return
     ],
     exception_table: [],
@@ -185,30 +188,6 @@ Context.prototype.resume = function() {
   this.start(this.stopFrame);
 }
 
-Context.prototype.wait = function(obj) {
-  if (!obj.waiters)
-    obj.waiters = [];
-  obj.waiters.push(this);
-  throw VM.Pause;
-}
-
-Context.prototype.notify = function(obj) {
-  if (obj.waiters && obj.waiters.length) {
-    if (!obj.ready)
-      obj.ready = [];
-    obj.ready.push(obj.waiters.pop());
-  }
-  if (!obj.ready || !obj.ready.length)
-    return;
-  var ctx = obj.ready.pop();
-  window.setZeroTimeout(VM.execute.bind(null, ctx));
-}
-
-Context.prototype.notifyAll = function(obj) {
-  while ((obj.waiters && obj.waiters.length) || (obj.ready && obj.ready.length))
-    this.notify(obj);
-}
-
 Context.prototype.monitorEnter = function(obj) {
   var lock = obj.lock;
   if (!lock) {
@@ -219,7 +198,10 @@ Context.prototype.monitorEnter = function(obj) {
     ++lock.count;
     return;
   }
-  this.wait(obj);
+  if (!obj.ready)
+    obj.ready = [];
+  obj.ready.push(this);
+  throw VM.Pause;
 }
 
 Context.prototype.monitorExit = function(obj) {
@@ -232,5 +214,29 @@ Context.prototype.monitorExit = function(obj) {
     return;
   }
   obj.lock = null;
-  this.notifyAll(obj);
+  if (obj.ready && obj.ready.length) {
+    var ctx = obj.ready.pop();
+    ctx.monitorEnter(obj);
+    ctx.resume();
+  }
+}
+
+Context.prototype.wait = function(obj, timeout) {
+  if (!obj.lock || obj.lock.thread !== this.thread || obj.lock.count !== 1)
+    this.raiseException("java/lang/IllegalMonitorStateException");
+  this.monitorExit(obj);
+  if (!obj.waiting)
+    obj.waiting = [];
+  obj.waiting.push(obj);
+  throw VM.Pause;
+}
+
+Context.prototype.notify = function(obj, notifyAll) {
+  if (!obj.lock || obj.lock.thread !== this.thread)
+    this.raiseException("java/lang/IllegalMonitorStateException");
+  while (obj.waiting && obj.waiting.length) {
+    obj.ready.push(obj.waiting.pop());
+    if (!notifyAll)
+      break;
+  }
 }

native.js

@@ -103,7 +103,6 @@ Native["java/lang/Object.hashCode.()I"] = function(ctx, stack) {
     var hashCode = obj.hashCode;
     while (!hashCode)
         hashCode = obj.hashCode = util.id();
-    console.log(hashCode);
     stack.push(hashCode);
 }
 
@@ -113,7 +112,11 @@ Native["java/lang/Object.wait.(J)V"] = function(ctx, stack) {
 }
 
 Native["java/lang/Class.invoke_clinit.()V"] = function(ctx, stack) {
-    var classInfo = stack.pop().vmClass;
+    var classObject = stack.pop();
+    var classInfo = classObject.vmClass;
+    if (classInfo.initialized || classInfo.pending)
+        return;
+    classInfo.pending = true;
     var clinit = CLASSES.getMethod(classInfo, "<clinit>", "()V", true);
     if (clinit)
         ctx.pushFrame(clinit, 0);
@@ -125,9 +128,10 @@ Native["java/lang/Class.invoke_clinit.()V"] = function(ctx, stack) {
 Native["java/lang/Class.init9.()V"] = function(ctx, stack) {
     var classObject = stack.pop();
     var classInfo = classObject.vmClass;
+    if (classInfo.initialized)
+        return;
+    classInfo.pending = false;
     classInfo.initialized = true;
-    classInfo.thread = null;
-    ctx.notifyAll(classObject);
 }
 
 Native["java/lang/Class.getName.()Ljava/lang/String;"] = function(ctx, stack) {

vm.js

@@ -95,13 +95,6 @@ VM.execute = function(ctx) {
     function classInitCheck(classInfo, ip) {
         if (classInfo.initialized)
             return;
-        if (classInfo.thread) {
-            // Nothing to do if class initialization is currently in progress on this thread.
-            if (classInfo.thread === ctx.thread)
-                return;
-            ctx.wait(classInfo.getClassObject());
-            // not reached
-        }
         frame.ip = ip;
         ctx.pushClassInitFrame(classInfo);
         throw VM.Yield;