#vulnerable code 
                                public void log(final LogEvent event) {

        counter.incrementAndGet();
        try {
            if (isFiltered(event)) {
                return;
            }

            event.setIncludeLocation(isIncludeLocation());

            callAppenders(event);

            if (additive && parent != null) {
                parent.log(event);
            }
        } finally {
            if (counter.decrementAndGet() == 0) {
                shutdownLock.lock();
                try {
                    if (shutdown.get()) {
                        noLogEvents.signalAll();
                    }
                } finally {
                    shutdownLock.unlock();
                }
            }
        }
    } 
                            #location 13 
                            #vulnerability type THREAD_SAFETY_VIOLATION
#fixed code
                                public void log(final LogEvent event) {
        beforeLogEvent();
        try {
            if (!isFiltered(event)) {
                processLogEvent(event);
            }
        } finally {
            afterLogEvent();
        }
    }