Locking strategy with PropertyChangeListener

I've defined a class with a number of "observable" properties. Internally the class contains a single thread that performs I/O; e.g. public class Foo { private final PropertyChangeSupport support; private State state; public Foo() { this.support = new PropertyChangeSupport(this); } public synchronized State getState() { return state; } public synchronized void setState(State state) { if (this.state != state) { State oldState = this.state; this.state = state; // Fire property change *whilst still holding the lock*. support.firePropertyChange("state", oldState, state); } } public synchronized void start() { // Start I/O Thread, which will call setState(State) in some circumstances. new Thread(new Runnable() ... } } My question is: Should I avoid firing property change events whilst holding onto the class's lock? ... *or* perhaps I should be firing property change events from a single dedicated thread (e.g. "event-multicaster" thread)? The current design is resulting in a deadlock whereby thread A takes out a lock on an external class: `Bar`, and then tries to call a method on `Foo` and take out a second lock. However, at the same time the I/O thread calls `setState(State)` obtaining the lock on `Foo`, which propagates a property changed event out to the containing class `Bar` and attempts to get the lock on this class ... resulting in deadlock. In other words, the property change callback design means I cannot effectively control the order in which my locks are being obtained. My current workaround is to make state `volatile` and remove the `synchronized` keywords but this seems like a kludge; for one thing it means the order in which the property change events are fired is not guaranteed.

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