[rvm-research] BufferedOutputStream errors during VM exiting

[Jian Li <jl...@su...>]

Hello,

When I tried to hook a object using BufferedOutputStream to ExitMonitor in 
VM_Callback, it raise a NullPointerException from 
java.lang.ThreadLocalMap. (A full exception and source code attached)

There is also a similar exception described in
http://jira.codehaus.org/browse/RVM-342, although it is in different 
situation.

This problem seems to happen after System.exit called, because a similar 
code, which writes a chunk of data in VM.sysExit through 
BufferedOutputStream, executed successfully without any exception. 
However, if the program was terminated through System.exit(), 
NullPointerException will thrown from ThreadLocalMap.get().

The root for this problem seems ThreadLocalMap constructor would allocates 
memory for field "private Entry[] entries".

Do you know there is anything that would cause the constructor 
ThreadLocalMap would not complete successfully? Or is it something to do 
with System.exit()? Do you know there is a way that I can still use 
BufferedOutputStream during VM shutting down? Many thanks!

Cheers,
Jian

------------------------------------
Exception from the code:
Exception in thread "MainThread": java.lang.NullPointerException
    at java.lang.ThreadLocalMap.get(ThreadLocalMap.java:212)
    at java.lang.ThreadLocal.get(ThreadLocal.java:146)
    at gnu.java.nio.VMChannel$LocalByteArray.get(VMChannel.java:183)
    at gnu.java.nio.VMChannel.write(VMChannel.java:397)
    at gnu.java.nio.VMChannel.write(VMChannel.java:409)
    at gnu.java.nio.VMChannel.write(VMChannel.java:421)
    at gnu.java.nio.FileChannelImpl.write(FileChannelImpl.java:261)
    at java.io.FileOutputStream.write(FileOutputStream.java:283)
    at java.io.BufferedOutputStream.flush(BufferedOutputStream.java:109)
    at java.io.BufferedOutputStream.write(BufferedOutputStream.java:152)
    at java.io.DataOutputStream.write(DataOutputStream.java:115)
    at ExitCallback.notifyExit(Test.java:27)
    at org.jikesrvm.VM_Callbacks.notifyExit(VM_Callbacks.java:801)
    at org.jikesrvm.VM.sysExit(VM.java:2108)
    at java.lang.VMRuntime.exit(VMRuntime.java:97)
    at java.lang.Runtime.halt(Runtime.java:399)
    at java.lang.Runtime.exit(Runtime.java:174)
    at java.lang.System.exit(System.java:577)
We got an uncaught exception while (recursively) handling 1 uncaught 
exception.
Exception in thread "MainThread": java.lang.NullPointerException
    at java.lang.Thread.die(Thread.java:1066)
    at java.lang.JikesRVMSupport.threadDied(JikesRVMSupport.java:101)
    at org.jikesrvm.scheduler.VM_Thread.terminate(VM_Thread.java:675)
    at 
org.jikesrvm.scheduler.VM_Thread.handleUncaughtException(VM_Thread.java:1837)
    at 
org.jikesrvm.runtime.VM_Runtime.deliverException(VM_Runtime.java:966)
    at org.jikesrvm.runtime.VM_Runtime.athrow(VM_Runtime.java:620)
    at org.jikesrvm.VM_Callbacks.notifyExit(VM_Callbacks.java:803)
    at org.jikesrvm.VM.sysExit(VM.java:2108)
    at java.lang.VMRuntime.exit(VMRuntime.java:97)
    at java.lang.Runtime.halt(Runtime.java:399)
    at java.lang.Runtime.exit(Runtime.java:174)
    at java.lang.System.exit(System.java:577)
JikesRVM: internal error: recursive use of hardware exception registers 
(exiting)

-- Stack --
    at [0x712f5928] Ljava/lang/JikesRVMSupport; threadDied(Ljava/lang/Thread;)V at line 101
    at [0x712f5950] Lorg/jikesrvm/scheduler/VM_Thread; terminate()V at line 675
    at [0x712f5970] Lorg/jikesrvm/scheduler/VM_Thread; handleUncaughtException(Ljava/lang/Throwable;)V at line 1837
    at [0x712f59b8] Lorg/jikesrvm/runtime/VM_Runtime; deliverException(Ljava/lang/Throwable;Lorg/jikesrvm/ArchitectureSpecific$VM_Registers;)V 
at line 966
    at [0x712f59f8] Lorg/jikesrvm/runtime/VM_Runtime; deliverHardwareException(II)V at line 746
    at [0x712f5a0c] <hardware trap>
    at [0x71328e18] Ljava/lang/Thread; die()V at line 1066
    at [0x71328e34] Ljava/lang/JikesRVMSupport; threadDied(Ljava/lang/Thread;)V at line 101
    at [0x71328e5c] Lorg/jikesrvm/scheduler/VM_Thread; terminate()V at line 675
    at [0x71328e7c] Lorg/jikesrvm/scheduler/VM_Thread; handleUncaughtException(Ljava/lang/Throwable;)V at line 1837
    at [0x71328ec4] Lorg/jikesrvm/runtime/VM_Runtime; deliverException(Ljava/lang/Throwable;Lorg/jikesrvm/ArchitectureSpecific$VM_Registers;)V 
at line 966
    at [0x71328ee8] Lorg/jikesrvm/runtime/VM_Runtime; athrow(Ljava/lang/Throwable;)V at line 620
    at [0x71328f10] Lorg/jikesrvm/VM_Callbacks; notifyExit(I)V at line 803
    at [0x71328f2c] Lorg/jikesrvm/VM; sysExit(I)V at line 2108
    at [0x71328f48] Ljava/lang/VMRuntime; exit(I)V at line 97
    at [0x71328f6c] Ljava/lang/Runtime; halt(I)V at line 399
    at [0x71328f98] Ljava/lang/Runtime; exit(I)V at line 174
    at [0x71328fb8] Ljava/lang/System; exit(I)V at line 577
    at [0x71328fe0] Lorg/jikesrvm/scheduler/VM_Thread; terminate()V at line 749
    at [0x71329000] Lorg/jikesrvm/scheduler/VM_Thread; startoff()V at line 616
Proc 1: Thread 11: VM.sysExit(): We're in an (unambiguously) recursive call to VM.sysExit(), 2 deep

----------------------------------------------------------------
Code produced the exceptions:

import java.io.IOException;
import java.io.DataOutputStream;
import java.io.FileOutputStream;
import java.io.BufferedOutputStream;

import org.jikesrvm.VM;
import org.jikesrvm.VM_Callbacks;
import org.jikesrvm.VM_Callbacks.ExitMonitor;

public class Test extends Action {
   public static void main(String[] args) {
     VM_Callbacks.addExitMonitor(new ExitCallback());
//     VM.sysExit(0);
   }
}

class ExitCallback implements ExitMonitor {
   public void notifyExit(int n) {
     System.out.println("VM Exiting.");

     try {
       FileOutputStream fos = new FileOutputStream("test.tmp");
       BufferedOutputStream bos = new BufferedOutputStream(fos);
       DataOutputStream dos = new DataOutputStream(bos);

       for (int i = 0; i < 4000; i++)
         dos.write(0xF00D);

       dos.close();
       bos.close();
       fos.close();

     } catch (IOException e) {
       e.printStackTrace();
     }
   }
}