Add a VMLangAccess method to create threads

Added a package access method java.lang.Thread:Thread(Runnable runnable,
String threadName, boolean isSystemThreadGroup, boolean
inheritThreadLocals, boolean isDaemon, ClassLoader contextClassLoader)
which allows callers outside of java.lang package to create threads with
such options via VMLangAccess interface.
Specifically this supports java.io.ClassCache to create a thread that
belongs to the system thread group, and not inherit ThreadLocals.

Signed-off-by: Jason Feng <[email protected]>

jcl/src/java.base/share/classes/com/ibm/oti/vm/VMLangAccess.java

@@ -11,7 +11,7 @@
 
 
 /*******************************************************************************
- * Copyright (c) 2012, 2018 IBM Corp. and others
+ * Copyright (c) 2012, 2019 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -155,4 +155,18 @@ public interface VMLangAccess {
 	public void addPackageToList(Class<?> newClass, ClassLoader loader);
 	/*[ENDIF] Sidecar19-SE */
 
+	/**
+	 * Create a thread that it has runnable as its run object, has threadName as its name, has contextClassLoader as its context ClassLoader,
+	 * has an option to be part of system thread group, has an option to inherit ThreadLocals or not, and has an option to set isDaemon.
+	 * 
+	 * @param       runnable                A java.lang.Runnable whose method <code>run</code> will be executed by the new Thread
+	 * @param       threadName              Name for the Thread being created
+	 * @param       isSystemThreadGroup     A boolean indicating whether the thread to be created belongs to the system thread group
+	 * @param       inheritThreadLocals     A boolean indicating whether to inherit initial values for inheritable thread-local variables
+	 * @param       isDaemon                Indicates whether or not the Thread being created is a daemon thread
+	 * @param       contextClassLoader      The context ClassLoader
+	 * 
+	 * @return      A java.lang.Thread created
+	 */
+	public Thread createThread(Runnable runnable, String threadName, boolean isSystemThreadGroup, boolean inheritThreadLocals, boolean isDaemon, ClassLoader contextClassLoader);
 }

jcl/src/java.base/share/classes/java/lang/Thread.java

@@ -349,6 +349,12 @@ public Thread(ThreadGroup group, Runnable runnable, String threadName) {
 	this(group, runnable, threadName, null, true);
 }
 
+Thread(Runnable runnable, String threadName, boolean isSystemThreadGroup, boolean inheritThreadLocals, boolean isDaemon, ClassLoader contextClassLoader) {
+	this(isSystemThreadGroup ? systemThreadGroup : null, runnable, threadName, null, inheritThreadLocals);
+	this.isDaemon = isDaemon;
+	this.contextClassLoader = contextClassLoader;
+}
+
 private Thread(ThreadGroup group, Runnable runnable, String threadName, AccessControlContext acc, boolean inheritThreadLocals) {
 	super();
 	/*[PR 1FEVFSU] Re-arrange method so that common code to this constructor and the private one the VM calls can be put in a separate method */

jcl/src/java.base/share/classes/java/lang/VMAccess.java

@@ -2,7 +2,7 @@
 package java.lang;
 
 /*******************************************************************************
- * Copyright (c) 2012, 2018 IBM Corp. and others
+ * Copyright (c) 2012, 2019 IBM Corp. and others
  *
  * This program and the accompanying materials are made available under
  * the terms of the Eclipse Public License 2.0 which accompanies this
@@ -216,4 +216,8 @@ public void addPackageToList(java.lang.Class<?> newClass, ClassLoader loader) {
 	}
 	/*[ENDIF] Sidecar19-SE */
 
+	@Override
+	public Thread createThread(Runnable runnable, String threadName, boolean isSystemThreadGroup, boolean inheritThreadLocals, boolean isDaemon, ClassLoader contextClassLoader) {
+		return new Thread(runnable, threadName, isSystemThreadGroup, inheritThreadLocals, isDaemon, contextClassLoader);
+	}
 }