Concurrent modification exception inside fully synchronized code

Question

Hello,
We have a private list
private LinkedList<ConnectionChannel> channels = new LinkedList<ConnectionChannel>();that is accessed by multiple threads. One is traversing the items and operating on them, while another thread is adding and removing items to the list. Each such access to the list is protected with
synchronized(channels) {
} scopes so that no simultanious access to this list is possible.
We do however get Concurrent Modification excpetions on this list when we do performance tests with heavy load on the sun server + heavy load on the java server itself. I cannot understand this problem in any other way that this must be a problem with the virtual machine! I know you guys probably will object to this furiously, but I am 100% sure that there is no logical error in my code.
We're running on jre 1.5..0_03. uname -a on my solaris host gives me:
SunOS trinity 5.8 Generic_108528-27 sun4u sparc SUNW,Sun-Fire-480R.
Best regards,
Helge Fredriksen

Answer 1

I'm very sure about this, yes. Here's all blocks where the list is used:
        synchronized (channels) {
            logger.info("Connecting observer channel from client at " + token.getSource());
            channels.add(new ConnectionChannel(token, globalObserver));
       synchronized (channels) {
            if (logger.isDebugEnabled()) {
                logger.debug("Sending local event to processing in " + channels.size() + " parallel channel(s)");
            for (ConnectionChannel connectionChanel : channels) {
                connectionChanel.send(event);
        synchronized (channels) {
            for (Iterator<ConnectionChannel> iterator = channels.iterator(); iterator.hasNext();) {
                ConnectionChannel connectionChannel = iterator.next();
                if (connectionChannel.getToken().getId().equals(token.getId())) {
                    iterator.remove();
                    logger.info("Removing connection channel to " + token.getSource());
                    return;
        }and
        synchronized (channels) {
            for (ConnectionChannel channel : channels) {
                channel.flush(5000);
        }