MMO game server brain loop

I'm writing up a game server on which thread-safety is very important, basically for this approach I've decided to move my entire server in a single brain loop which handles everything in a single thread, connections are ran separately in their own separate thread, whenever a packet is received, the brain loop is signaled so it doesn't have to wait for the entire interval.

This is truly the best approach I could come up with, given my server is filled with pointers everywhere, and invalidation would kill my player base.

#define GAME_BEAT 50

void Game::brain() {
    int64_t connectionsTimeCounter = 0;
    int64_t decayTimeCounter = 0;
    int64_t releasePointersCounter = 0;
    int64_t creaturesTimeCounter = 0;
    int64_t roundNr = getServerMilliseconds();

    while (isGameRunning() || isGameStarting()) {
        gameSignal.wait(GAME_BEAT);

        int64_t delay = getServerMilliseconds() - roundNr;
        roundNr = getServerMilliseconds();

        // Receive packets from connections with data available to be read (non-blocking)
        // when data is available to be read, the connection which was previously ran in a different thread
        // will be signaled to read packet data and store it in a variable
        // say, a packet for "player talk" was sent, then the function below "moveCreatures" would handle this action
        g_server.receiveData();

        connectionsTimeCounter += delay;
        if (connectionsTimeCounter >= 1000) {
            // This function closes invalid connections/closed connections
            g_server.processConnections();
        }

        decayTimeCounter += delay;
        if (connectionsTimeCounter >= 1500) {
            decayItems(delay);
        }

        releasePointersCounter += delay;
        if (releasePointersCounter >= 1000) {
            // This function simply calls a "delete" to removed objects from the game
            releaseObjects();
        }

        creaturesTimeCounter += delay;
        if (creaturesTimeCounter >= 1000) {
            // Processes creatures idle status
            processCreatures(delay);
        }

        // Moves creatures, players, talking, moving, etc ...
        moveCreatures();

        // Sends all pending packets to be sent to active connections
        g_server.sendAllData();
    }
}

That is pretty much the only way I found for my server to be thread-safe, since I did experienced a few crashes because when connections sent a particular packet (say player move item), it would invalidate other connections from doing so