Hi,
An old issue has resurfaced because of a change in AWT. AWT, now, on Mac
OS X, attaches a system graphics thread to the running VM, using
JNI_AttachCurrentThread. This change can result in a NPE, if a security
manager is installed, and the security manager tries to print the name
of the current thread.
In this case, attaching a thread to the VM, the j.l.Thread instance/oop
is created by the VM in allocate_threadObj(), and then its constructor
is run. At this point almost everything has been created for the thread,
jni env, etc, so it can query currentThread() to retrieve itself. (Note:
this is unusual. Typically the thread running the j.l.Thread constructor
is not itself.) Since the j.l.Thread oop was allocated directly by the
VM, its fields, other than those directly set by allocate_threadObj(),
are not initialized.
The call out from Thread.init to the security manager is problematic as
the partially constructed thread can be retrieved through
Thread.currentThread. Some of our internal tests run into a problem when
the security manager tries to print the name of the thread, i.e. NPE.
Clearly there are other concerns of accessing a partially constructed
thread, not just the thread name, but it seems reasonable to simply move
the setting of the name to the beginning of the init() method.
I propose the following change for JDK 9, with the intention of backport
exactly to JDK 8. Long term this should be revisited in JDK 9.
diff --git a/src/share/classes/java/lang/Thread.java
b/src/share/classes/java/lang/Thread.java
--- a/src/share/classes/java/lang/Thread.java
+++ b/src/share/classes/java/lang/Thread.java
@@ -366,6 +366,8 @@
throw new NullPointerException("name cannot be null");
}
+ this.name = name.toCharArray();
+
Thread parent = currentThread();
SecurityManager security = System.getSecurityManager();
if (g == null) {
@@ -402,7 +404,6 @@
this.group = g;
this.daemon = parent.isDaemon();
this.priority = parent.getPriority();
- this.name = name.toCharArray();
if (security == null || isCCLOverridden(parent.getClass()))
this.contextClassLoader = parent.getContextClassLoader();
else
-Chris.
