Function killRDBChild

src/rdb.cpp:3689–3716

Kill the RDB saving child using SIGUSR1 (so that the parent will know * the child did not exit for sn error, but because we wanted), and performs * the cleanup needed. */

 * the child did not exit for sn error, but because we wanted), and performs
 * the cleanup needed. */
void killRDBChild(bool fSynchronous) {
    serverAssert(GlobalLocksAcquired());

    if (cserver.fForkBgSave) {
        kill(g_pserver->child_pid,SIGUSR1);
    } else { 
        g_pserver->rdbThreadVars.fRdbThreadCancel = true;
        if (g_pserver->rdb_child_type == RDB_CHILD_TYPE_SOCKET) {
            // Wake up the thread so it can exit
            auto t = write(g_pserver->rdb_child_exit_pipe, &cserver.fForkBgSave, 1);
            UNUSED(t);
            // Flush out the rdb pipe in case the writer thread is blocked
            unblockChildThreadIfNecessary();
        }
        if (fSynchronous)
        {
            aeReleaseLock();
            serverAssert(!GlobalLocksAcquired());
            void *result;
            int err = pthread_join(g_pserver->rdbThreadVars.rdb_child_thread, &result);
            if (err) {
                serverLog(LL_WARNING, "RDB child thread could not be joined: %s", strerror(err));
            }
            g_pserver->rdbThreadVars.fRdbThreadCancel = false;
            aeAcquireLock();
        }
    }
}

struct rdbSaveSocketThreadArgs
{