AbstractNioBossPool may initialize more than once?

[MichaelScofield]

The following code snippets are in 3.9.4.final.
In org.jboss.netty.channel.socket.nio.AbstractNioBossPool, method

protected void init() {
    if (initialized) {
        throw new IllegalStateException("initialized already");
    }
    initialized = true;

    ...
}

where the definition of variable "initialized" is

private volatile boolean initialized;

Is there concurrency hazard that may cause the init() method to be called more than once?

If 2 threads were call the init() method simultaneously. Thread1 checks that if(initialized) is false and hang, Thread2 now checks if(initialized) is false and do the initialization. Then the Thread1 is back to run, and do the initialization again.

I think it's much better to make the variable "initialized" AtomicBoolean, because you can use atomic CAS to do the initialization exactly once:

private final AtomicBoolean initialized = new AtomicBoolean(false);

protected void init() {
    if (!initialized.compareAndSet(false, true)) {
        throw new IllegalStateException("initialized already");
    }

    ....
}

[normanmaurer]

@MichaelScofield sounds right... could you come up with PR ?

[MichaelScofield]

I've created a PR to branch 3.9:

#3253

[normanmaurer]

Fixed by #3253