Looking into the big loop code, it may happen that the worker process may close the keepalive connection before consuming any pending read events?

for ( ;; ) {

if (ngx_exiting) {
if (ngx_event_no_timers_left() == NGX_OK) {
ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "exiting");
ngx_worker_process_exit(cycle);
}
}

ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "worker cycle");

ngx_process_events_and_timers(cycle);

if (ngx_terminate) {
ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "exiting");
ngx_worker_process_exit(cycle);
}

if (ngx_quit) {
ngx_quit = 0;
ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0,
"gracefully shutting down");
ngx_setproctitle("worker process is shutting down");

if (!ngx_exiting) {
ngx_exiting = 1;
ngx_set_shutdown_timer(cycle);
ngx_close_listening_sockets(cycle);
ngx_close_idle_connections(cycle); <--what if a read event is coming when goes here?
}
}