JDK-8027351: (ref) Base's class finalize method not invoked if a private finalize method exists in its subclass

[Peter Levart]

On 11/04/2013 05:45 AM, Mandy Chung wrote:
>> That said I think Peter may be right that there could be races with 
>> agents triggerring explicit finalization requests early in the VM 
>> initialization process - which means any blocking operation dependent 
>> on other parts of the initialization sequence could be problematic.
>
> Hmm... agents calling System.runFinalization during startup - like 
> Alan described, the agent is playing fire.
>
> The potential issue that could happen is that during the VM 
> initialization the heap is so small that triggers GC and also the 
> startup code has finalizers and those objects with finalizers are 
> awaiting for finalization in order for the sufficient memory to be 
> freed up.  The VM initialization couldn't get completed and the 
> Finalizer thread is blocked and thus due to insufficient memory, 
> eventually it would get out of memory.  An agent instrumenting classes 
> early in the startup and creates lots of objects and finalizers, that 
> might also cause problem.
>
> I think it's good to have the secondary finalizer thread to call 
> ensureAccessAvailable (with some modification to ensure jla is 
> initialized). 

Hi Mandy,

What about the following helper class in java.lang package:


package java.lang;

import sun.misc.VM;
import sun.reflect.CallerSensitive;
import sun.reflect.Reflection;

/**
  * Access to protected Object methods. Only accessible to system classes.
  */
public final class ObjectAccess {
     private static final ObjectAccess theInstance = new ObjectAccess();

     @CallerSensitive
     public static ObjectAccess getInstance() {
         Class<?> caller = Reflection.getCallerClass();
         if (!VM.isSystemDomainLoader(caller.getClassLoader()))
             throw new SecurityException("ObjectAccess");
         return theInstance;
     }

     public void finalizeObject(Object o) throws Throwable {
         o.finalize();
     }

     public Object cloneObject(Object o) throws CloneNotSupportedException {
         return o.clone();
     }
}


...is such code permissible to be executed in the Finalizer's static 
initializer even before VM.isBooted() ?


Regards, Peter