Stuck Inside Native Method

Question

I have developed some Java code to call a third party DLL using JNI. Most of the time everything works as expected, but once in a while (generally after several days of processing) my program hangs. The root cause appears to be related to an intermittent issue with the driver that I am calling, something that I have no control over. When I perform a thread dump I can see that the thread is "stuck" inside the native method that I am calling. I am able to detect the hangup using a timer, and even obtain the "stuck" thread, but I cannot kick it back into life...or kill it in any way. Does anyone have any ideas?
My code that is calling the native method is as follows:
public void process() {
    System.out.println("Hello world from Java");
    Timer timer = new Timer();
    timer.schedule(new MyTimerTask(), 1000);
    myNativeMethod();
    System.out.println("Goodbye world from Java");
}And the code for my timer task is as follows:
public class MyTimerTask extends TimerTask {
    @Override
    public void run() {
        System.out.println("Timeout");
        ThreadGroup tg = Thread.currentThread().getThreadGroup();
        Thread[] list = new Thread[tg.activeCount()];
        tg.enumerate(list);
        for (Thread t : list) {
            System.out.println(t);
            System.out.println("---------------------------------------");
            StackTraceElement[] st = t.getStackTrace();
            for (StackTraceElement ste : st) {
                System.out.println(ste);
                if (ste.getMethodName().equals("myNativeMethod") && ste.isNativeMethod()) {
                    System.out.println("stuck thread " + t.getName() + " detected!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
                    t.interrupt();
                    break;
}

Answer 1

StuartyBoarder wrote:
a) As it's a server I must use a separate process to communicate with a DDL because that's the only way to communicate with a DLL inside the serverNo
b) As it's a server I must use a separate process to communicate with a DLL if I want to be able to kill a stuck process
Absolutely.
I am assuming that you mean b), which is not really an option A process is a process. Doesn't matter what it runs.
An advantage that hasn't been mentioned in terms of a separate process is that if the dll has a system exception it will cause the process to exit. And there is no way to stop that. If that process is your JBoss server then it will exit. Which probably isn't what you want.
As a separate process if if exits all you need to is detect that (via correct usage of Process) and then just start it up again.