RFR [9] 8031050: [macosx] Crash while awt starting

[Mandy Chung]

On 2/3/2014 5:18 AM, Chris Hegarty wrote:
> 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.

This looks okay as a short-term fix to address this particular issue 
(accessing the name of a partially constructed Thread object).

Mandy