Re: Deadlocks

From:

Daniel Pitts <newsgroup.spamfilter@virtualinfinity.net>

Newsgroups:

comp.lang.java.programmer

Date:

Fri, 02 Nov 2007 13:20:30 -0700

Message-ID:

<5qmdnat7Jd19G7banZ2dnUVZ_oWdnZ2d@wavecable.com>

getsanjay.sharma@gmail.com wrote:

Hello to all Java programmer out there.

I am currently reading about deadlocks and so wrote a small program
which would simulate a deadlock. But I have come across a very weird
behavior in the sense that it seems that Two threads are acquiring a
lock on an object at the same time. From what I know so far, each
object has a single lock object which a thread has to acquire to enter
the critical section. So why the given output which seems to say that
both Thread one and Thread two have acquired a lock on the same
object?

Here is a simple example of deadlock:
public class Dead implements Runnable {
   public static final Object lock = new Object();
   public static void main(String...args) throws Exception {
      synchronized (lock) {
          final Thread thread = new Thread(new Dead());
          thread.start();
          try {
              thread.join();
          } finally {
              System.exit(0);
          }
      }
   }

     public void run() {
         synchronized (lock) {
             System.out.println("This will never execute!");
         }
     }
}

I suggest you read the book Java Concurrency In Practice. It describes
common problems, correct solutions, and useful patterns for dealing with
concurrency. It is the most complete and understandable writing on the
matter that I have come across.
<http://virtualinfinity.net/wordpress/technical-book-recommendations/java-concurrency-in-practice/>

--
Daniel Pitts' Tech Blog: <http://virtualinfinity.net/wordpress/>