Function processEventsWhileBlocked

app/redis-6.2.6/src/networking.c:3406–3433

This function is called by Redis in order to process a few events from * time to time while blocked into some not interruptible operation. * This allows to reply to clients with the -LOADING error while loading the * data set at startup or after a full resynchronization with the master * and so forth. * * It calls the event loop in order to process a few events. Specifically we * try to cal

 *
 * The function returns the total number of events processed. */
void processEventsWhileBlocked(void) {
    int iterations = 4; /* See the function top-comment. */

    /* Update our cached time since it is used to create and update the last
     * interaction time with clients and for other important things. */
    updateCachedTime(0);

    /* Note: when we are processing events while blocked (for instance during
     * busy Lua scripts), we set a global flag. When such flag is set, we
     * avoid handling the read part of clients using threaded I/O.
     * See https://github.com/redis/redis/issues/6988 for more info. */
    ProcessingEventsWhileBlocked = 1;
    while (iterations--) {
        long long startval = server.events_processed_while_blocked;
        long long ae_events = aeProcessEvents(server.el,
            AE_FILE_EVENTS|AE_DONT_WAIT|
            AE_CALL_BEFORE_SLEEP|AE_CALL_AFTER_SLEEP);
        /* Note that server.events_processed_while_blocked will also get
         * incremeted by callbacks called by the event loop handlers. */
        server.events_processed_while_blocked += ae_events;
        long long events = server.events_processed_while_blocked - startval;
        if (!events) break;
    }

    whileBlockedCron();

    ProcessingEventsWhileBlocked = 0;
}

/* ==========================================================================
 * Threaded I/O