Presentation at Indigo Eclipse DemoCamp Bucharest

1. Eclipse DemoCamp Bucharest Deadlock Preventer - Test your java code for race conditions TeodorMadan CDT Commiter June 2011

2. Agenda Multitask Background Lock contention example Deadlock preventer Automating References.

3. Making application multithreaded Build UI Main Thread Indexing Source Control Search

4. Making application multithreaded UI Main Thread Build Search > 27000 locks acquired at Eclipse SDK start-up Indexing Source Control

5. Deadlocks Worker Thread 1 Lock A B? Worker Thread 2 Lock B A?

6. Removing followers Worker Thread 1 Lock A Lock B Worker Thread 2 Lock B Lock A

7. Lock contention example public synchronized void setProperty(Object newValue) { // A value = newValue; notifyPropertyChange(); } private void notifyPropertyChange() { synchronized(listeners) {// B for (IListener listener : listeners) listener.changed(); // C } }

8. Lock contention example public void setProperty(Object newValue) { synchronized(this) {// A value = newValue; } notifyPropertyChange(); } private void notifyPropertyChange() { synchronized(listeners) {// B for (IListener listener : listeners) listener.changed(); // C } }

9. Lock contention example public void setProperty(Object newValue) { synchronized(this) {// A value = newValue; } notifyPropertyChange(); } private void notifyPropertyChange() { IListener[] tmp; synchronized(listeners) {// B tmp = listeners.clone(); } for (IListener listener : tmp) listener.changed(); // C }

10. Deadlock preventer Shortcut to launch application with lock monitor agent activated Detects Inconsistent locking order while acquiring locks between all threads in JVM Extracts lock statistics for tuning lock contention

11. Deadlock preventer - Automation Adding the Deadlock preventer is as simple as adding the following two arguments to the “java” executable: -javaagent:path-toom.freescale.deadlockPreventer.wrapper_1.0.0om.freescale.deadlockpreventer.jar -Xbootclasspath/a:path-toom.freescale.deadlockPreventer.wrapper_1.0.0om.freescale.deadlockpreventer.jar;path-toavassist.wrapper_1.0.0avassist.jar By default just prints all inconsistent locks to console output. There’s a server version listening for the deadlock preventer monitor events

12. References Author blog http://sergebeauchamp.blogspot.com/ GitHub https://github.com/sbeauchamp/Deadlock-Preventer

13. Q & A