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*/
/*
* @test
* @bug 4757273
* @summary Test deadlock in MBeanServerDelegate listeners
* @author Eamonn McManus
* @modules java.management
* @run clean NotifDeadlockTest
* @run build NotifDeadlockTest
* @run main NotifDeadlockTest
*/
/*
* Test deadlock when a listener for an MBeanServerDelegate does a
* register or unregister of an MBean. Since such a listener is
* triggered by a register or unregister operation, deadlock scenarios
* are possible if there are any locks held while the listener is
* being dispatched.
*
* The flow of control looks rather like this:
*
* Thread 1:
* - MBeanServer.createMBean(..., objectName1);
* --- MBeanServerDelegate.sendNotification
* ----- XListener.handleNotification
* ------- create Thread 2
* ------- wait for Thread 2 to complete
*
* Thread 2:
* - MBeanServer.createMBean(..., objectName2);
* - end Thread 2
*
* If any locks are held by Thread 1 within createMBean or
* sendNotification, then Thread 2 can block waiting for them.
* Since Thread 1 is itself waiting for Thread 2, this is a deadlock.
*
* We test all four combinations of:
* (Thread1-create,Thread1-unregister) x (Thread2-create,Thread2-unregister)
*
* In the JMX 1.1 RI, all four tests fail. In the JMX 1.2 RI, all four
* tests should pass.
*/
import javax.management.*;
public class NotifDeadlockTest {
static ObjectName on1, on2, delName;
static {
try {
on1 = new ObjectName("thing:a=b");
on2 = new ObjectName("thing:c=d");
delName =
new ObjectName("JMImplementation:type=MBeanServerDelegate");
} catch (MalformedObjectNameException e) {
throw new Error();
}
}
static MBeanServer mbs;
static boolean timedOut;
/* This listener registers or unregisters the MBean called on2
when triggered. */
private static class XListener implements NotificationListener {
private boolean firstTime = true;
private final boolean register;
XListener(boolean register) {
this.register = register;
}
public void handleNotification(Notification not, Object handback) {
if (firstTime) {
firstTime = false;
Thread t = new Thread() {
public void run() {
try {
if (register) {
mbs.createMBean("javax.management.timer.Timer",
on2);
System.out.println("Listener created " + on2);
} else {
mbs.unregisterMBean(on2);
System.out.println("Listener removed " + on2);
}
} catch (Exception e) {
e.printStackTrace();
}
}
};
t.start();
try {
t.join(2000);
} catch (InterruptedException e) {
e.printStackTrace(); // should not happen
}
if (t.isAlive()) {
System.out.println("FAILURE: Wait timed out: " +
"probable deadlock");
timedOut = true;
}
}
}
}
public static void main(String[] args) throws Exception {
boolean success = true;
System.out.println("Test 1: in register notif, unregister an MBean");
timedOut = false;
mbs = MBeanServerFactory.createMBeanServer();
mbs.createMBean("javax.management.timer.Timer", on2);
mbs.addNotificationListener(delName, new XListener(false), null, null);
mbs.createMBean("javax.management.timer.Timer", on1);
MBeanServerFactory.releaseMBeanServer(mbs);
if (timedOut) {
success = false;
Thread.sleep(500);
// wait for the spawned thread to complete its work, probably
}
System.out.println("Test 1 completed");
System.out.println("Test 2: in unregister notif, unregister an MBean");
timedOut = false;
mbs = MBeanServerFactory.createMBeanServer();
mbs.createMBean("javax.management.timer.Timer", on1);
mbs.createMBean("javax.management.timer.Timer", on2);
mbs.addNotificationListener(delName, new XListener(false), null, null);
mbs.unregisterMBean(on1);
MBeanServerFactory.releaseMBeanServer(mbs);
if (timedOut) {
success = false;
Thread.sleep(500);
// wait for the spawned thread to complete its work, probably
}
System.out.println("Test 2 completed");
System.out.println("Test 3: in register notif, register an MBean");
timedOut = false;
mbs = MBeanServerFactory.createMBeanServer();
mbs.addNotificationListener(delName, new XListener(true), null, null);
mbs.createMBean("javax.management.timer.Timer", on1);
MBeanServerFactory.releaseMBeanServer(mbs);
if (timedOut) {
success = false;
Thread.sleep(500);
// wait for the spawned thread to complete its work, probably
}
System.out.println("Test 3 completed");
System.out.println("Test 4: in unregister notif, register an MBean");
timedOut = false;
mbs = MBeanServerFactory.createMBeanServer();
mbs.createMBean("javax.management.timer.Timer", on1);
mbs.addNotificationListener(delName, new XListener(true), null, null);
mbs.unregisterMBean(on1);
MBeanServerFactory.releaseMBeanServer(mbs);
if (timedOut) {
success = false;
Thread.sleep(500);
// wait for the spawned thread to complete its work, probably
}
System.out.println("Test 4 completed");
if (success)
System.out.println("Test passed");
else {
System.out.println("TEST FAILED: at least one subcase failed");
System.exit(1);
}
}
}