#vulnerable code 
                                @Override
    public void stop() {
        LOGGER.debug("Stopping LoggerContext[name={}, {}]...", getName(), this);
        configLock.lock();
        try {
            if (this.isStopped()) {
                return;
            }

            this.setStopping();
            try {
                Server.unregisterLoggerContext(getName()); // LOG4J2-406, LOG4J2-500
            } catch (final Exception ex) {
                LOGGER.error("Unable to unregister MBeans", ex);
            }
            if (shutdownCallback != null) {
                shutdownCallback.cancel();
                shutdownCallback = null;
            }
            final Configuration prev = configuration;
            configuration = NULL_CONFIGURATION;
            updateLoggers();
            prev.stop();
            externalContext = null;
            LogManager.getFactory().removeContext(this);
            this.setStopped();
        } finally {
            configLock.unlock();
        }
        LOGGER.debug("Stopped LoggerContext[name={}, {}]...", getName(), this);
    } 
                            #location 30 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                @Override
    public void stop() {
        stop(0, null);
    }