KT-4825 Implement "synchronized" properly via monitorenter/monitorexit

#KT-4825 Fixed

libraries/stdlib/src/kotlin/JLangJVM.kt

@@ -2,6 +2,7 @@ package kotlin
 
 import java.lang.annotation.Retention
 import java.lang.annotation.RetentionPolicy
+import kotlin.jvm.internal.unsafe.*
 import kotlin.jvm.internal.Intrinsic
 
 /**
@@ -24,7 +25,15 @@ public annotation class throws(vararg val exceptionClasses: Class<out Throwable>
 
 [Intrinsic("kotlin.javaClass.function")] fun <reified T> javaClass() : Class<T> = null as Class<T>
 
-[Intrinsic("kotlin.synchronized")] public fun <R> synchronized(lock: Any, block: () -> R): R = block()
+public inline fun <R> synchronized(lock: Any, block: () -> R): R {
+    monitorEnter(lock)
+    try {
+        return block()
+    }
+    finally {
+        monitorExit(lock)
+    }
+}
 
 public fun <T : Annotation> T.annotationType() : Class<out T> =
     (this as java.lang.annotation.Annotation).annotationType() as Class<out T>

libraries/stdlib/src/kotlin/jvm/internal/unsafe/monitor.kt

@@ -0,0 +1,25 @@
+/*
+ * Copyright 2010-2014 JetBrains s.r.o.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ * http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package kotlin.jvm.internal.unsafe
+
+import kotlin.jvm.internal.Intrinsic
+
+[Intrinsic("kotlin.jvm.internal.unsafe.monitorEnter")]
+public fun monitorEnter(monitor: Any): Unit = throw UnsupportedOperationException("This function can only be used privately")
+
+[Intrinsic("kotlin.jvm.internal.unsafe.monitorExit")]
+public fun monitorExit(monitor: Any): Unit = throw UnsupportedOperationException("This function can only be used privately")