void
ngx_master_process_cycle(ngx_cycle_t *cycle)
{char              *title;u_char            *p;size_t             size;ngx_int_t          i;ngx_uint_t         n, sigio;sigset_t           set;struct itimerval   itv;ngx_uint_t         live;ngx_msec_t         delay;ngx_listening_t   *ls;ngx_core_conf_t   *ccf;//信号处理设置工作sigemptyset(&set);sigaddset(&set, SIGCHLD);sigaddset(&set, SIGALRM);sigaddset(&set, SIGIO);sigaddset(&set, SIGINT);sigaddset(&set, ngx_signal_value(NGX_RECONFIGURE_SIGNAL));sigaddset(&set, ngx_signal_value(NGX_REOPEN_SIGNAL));sigaddset(&set, ngx_signal_value(NGX_NOACCEPT_SIGNAL));sigaddset(&set, ngx_signal_value(NGX_TERMINATE_SIGNAL));sigaddset(&set, ngx_signal_value(NGX_SHUTDOWN_SIGNAL));sigaddset(&set, ngx_signal_value(NGX_CHANGEBIN_SIGNAL));if (sigprocmask(SIG_BLOCK, &set, NULL) == -1) {ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,"sigprocmask() failed");}sigemptyset(&set);size = sizeof(master_process);for (i = 0; i < ngx_argc; i++) {size += ngx_strlen(ngx_argv[i]) + 1;}title = ngx_pnalloc(cycle->pool, size);p = ngx_cpymem(title, master_process, sizeof(master_process) - 1);for (i = 0; i < ngx_argc; i++) {*p++ = ' ';p = ngx_cpystrn(p, (u_char *) ngx_argv[i], size);}ngx_setproctitle(title);ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx, ngx_core_module);//其中包含了fork产生子进程的内容ngx_start_worker_processes(cycle, ccf->worker_processes,NGX_PROCESS_RESPAWN);//Cache管理进程与cache加载进程的主流程ngx_start_cache_manager_processes(cycle, 0);ngx_new_binary = 0;delay = 0;sigio = 0;live = 1;for ( ;; ) {//循环if (delay) {if (ngx_sigalrm) {sigio = 0;delay *= 2;ngx_sigalrm = 0;}ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,"termination cycle: %d", delay);itv.it_interval.tv_sec = 0;itv.it_interval.tv_usec = 0;itv.it_value.tv_sec = delay / 1000;itv.it_value.tv_usec = (delay % 1000 ) * 1000;if (setitimer(ITIMER_REAL, &itv, NULL) == -1) {ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,"setitimer() failed");}}ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "sigsuspend");sigsuspend(&set);//master进程休眠，等待接受信号被激活ngx_time_update();ngx_log_debug1(NGX_LOG_DEBUG_EVENT, cycle->log, 0,"wake up, sigio %i", sigio);//标志位为1表示需要监控所有子进程if (ngx_reap) {ngx_reap = 0;ngx_log_debug0(NGX_LOG_DEBUG_EVENT, cycle->log, 0, "reap children");live = ngx_reap_children(cycle);//管理子进程}//当live标志位为0（表示所有子进程已经退出）、ngx_terminate标志位为1或者ngx_quit标志位为1表示要退出master进程if (!live && (ngx_terminate || ngx_quit)) {ngx_master_process_exit(cycle);//退出master进程}//ngx_terminate标志位为1，强制关闭服务，发送TERM信号到所有子进程if (ngx_terminate) {if (delay == 0) {delay = 50;}if (sigio) {sigio--;continue;}sigio = ccf->worker_processes + 2 /* cache processes */;if (delay > 1000) {ngx_signal_worker_processes(cycle, SIGKILL);} else {ngx_signal_worker_processes(cycle,ngx_signal_value(NGX_TERMINATE_SIGNAL));}continue;}//ngx_quit标志位为1，优雅的关闭服务if (ngx_quit) {ngx_signal_worker_processes(cycle,ngx_signal_value(NGX_SHUTDOWN_SIGNAL));//向所有子进程发送quit信号ls = cycle->listening.elts;for (n = 0; n < cycle->listening.nelts; n++) {//关闭监听端口if (ngx_close_socket(ls[n].fd) == -1) {ngx_log_error(NGX_LOG_EMERG, cycle->log, ngx_socket_errno,ngx_close_socket_n " %V failed",&ls[n].addr_text);}}cycle->listening.nelts = 0;continue;}//ngx_reconfigure标志位为1，重新读取配置文件//nginx不会让原来的worker子进程再重新读取配置文件，其策略是重新初始化ngx_cycle_t结构体，用它来读取新的额配置文件//再创建新的额worker子进程，销毁旧的worker子进程if (ngx_reconfigure) {ngx_reconfigure = 0;//ngx_new_binary标志位为1，平滑升级Nginxif (ngx_new_binary) {ngx_start_worker_processes(cycle, ccf->worker_processes,NGX_PROCESS_RESPAWN);ngx_start_cache_manager_processes(cycle, 0);ngx_noaccepting = 0;continue;}ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "reconfiguring");//初始化ngx_cycle_t结构体cycle = ngx_init_cycle(cycle);if (cycle == NULL) {cycle = (ngx_cycle_t *) ngx_cycle;continue;}ngx_cycle = cycle;ccf = (ngx_core_conf_t *) ngx_get_conf(cycle->conf_ctx,ngx_core_module);//创建新的worker子进程ngx_start_worker_processes(cycle, ccf->worker_processes,NGX_PROCESS_JUST_RESPAWN);ngx_start_cache_manager_processes(cycle, 1);/* allow new processes to start */ngx_msleep(100);live = 1;//向所有子进程发送QUIT信号ngx_signal_worker_processes(cycle,ngx_signal_value(NGX_SHUTDOWN_SIGNAL));}//ngx_restart标志位在ngx_noaccepting（表示正在停止接受新的连接）为1的时候被设置为1.//重启子进程if (ngx_restart) {ngx_restart = 0;ngx_start_worker_processes(cycle, ccf->worker_processes,NGX_PROCESS_RESPAWN);ngx_start_cache_manager_processes(cycle, 0);live = 1;}//ngx_reopen标志位为1，重新打开所有文件if (ngx_reopen) {ngx_reopen = 0;ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "reopening logs");ngx_reopen_files(cycle, ccf->user);ngx_signal_worker_processes(cycle,ngx_signal_value(NGX_REOPEN_SIGNAL));}//平滑升级Nginxif (ngx_change_binary) {ngx_change_binary = 0;ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "changing binary");ngx_new_binary = ngx_exec_new_binary(cycle, ngx_argv);}//ngx_noaccept为1，表示所有子进程不再处理新的连接if (ngx_noaccept) {ngx_noaccept = 0;ngx_noaccepting = 1;ngx_signal_worker_processes(cycle,ngx_signal_value(NGX_SHUTDOWN_SIGNAL));}}
}

ngx_start_worker_processes函数：

static void
ngx_start_worker_processes(ngx_cycle_t *cycle, ngx_int_t n, ngx_int_t type)
{ngx_int_t      i;ngx_channel_t  ch;ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "start worker processes");ch.command = NGX_CMD_OPEN_CHANNEL;//循环创建n个worker子进程for (i = 0; i < n; i++) {//完成fok新进程的具体工作ngx_spawn_process(cycle, ngx_worker_process_cycle,(void *) (intptr_t) i, "worker process", type);//全局数组ngx_processes就是用来存储每个子进程的相关信息，如：pid，channel，进程做具体事情的接口指针等等，这些信息就是用结构体ngx_process_t来描述的。ch.pid = ngx_processes[ngx_process_slot].pid;ch.slot = ngx_process_slot;ch.fd = ngx_processes[ngx_process_slot].channel[0];/*在ngx_spawn_process创建好一个worker进程返回后，master进程就将worker进程的pid、worker进程在ngx_processes数组中的位置及channel[0]传递给前面已经创建好的worker进程，然后继续循环开始创建下一个worker进程。刚提到一个channel[0]，这里简单说明一下：channel就是一个能够存储2个整型元素的数组而已，这个channel数组就是用于socketpair函数创建一个进程间通道之用的。master和worker进程以及worker进程之间都可以通过这样的一个通道进行通信，这个通道就是在ngx_spawn_process函数中fork之前调用socketpair创建的。*/ngx_pass_open_channel(cycle, &ch);}
}

ngx_spawn_process函数：

//参数解释：
//cycle：nginx框架所围绕的核心结构体
//proc：子进程中将要执行的工作循环
//data：参数
//name：子进程名字
ngx_pid_t
ngx_spawn_process(ngx_cycle_t *cycle, ngx_spawn_proc_pt proc, void *data,char *name, ngx_int_t respawn)
{u_long     on;ngx_pid_t  pid;ngx_int_t  s;if (respawn >= 0) {s = respawn;} else {for (s = 0; s < ngx_last_process; s++) {if (ngx_processes[s].pid == -1) {break;}}if (s == NGX_MAX_PROCESSES) {ngx_log_error(NGX_LOG_ALERT, cycle->log, 0,"no more than %d processes can be spawned",NGX_MAX_PROCESSES);return NGX_INVALID_PID;}}if (respawn != NGX_PROCESS_DETACHED) {/* Solaris 9 still has no AF_LOCAL *///创建父子进程间通信的套接字对（基于TCP）if (socketpair(AF_UNIX, SOCK_STREAM, 0, ngx_processes[s].channel) == -1){ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,"socketpair() failed while spawning \"%s\"", name);return NGX_INVALID_PID;}ngx_log_debug2(NGX_LOG_DEBUG_CORE, cycle->log, 0,"channel %d:%d",ngx_processes[s].channel[0],ngx_processes[s].channel[1]);//设置为非阻塞模式if (ngx_nonblocking(ngx_processes[s].channel[0]) == -1) {ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,ngx_nonblocking_n " failed while spawning \"%s\"",name);ngx_close_channel(ngx_processes[s].channel, cycle->log);return NGX_INVALID_PID;}if (ngx_nonblocking(ngx_processes[s].channel[1]) == -1) {ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,ngx_nonblocking_n " failed while spawning \"%s\"",name);ngx_close_channel(ngx_processes[s].channel, cycle->log);return NGX_INVALID_PID;}on = 1;if (ioctl(ngx_processes[s].channel[0], FIOASYNC, &on) == -1) {ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,"ioctl(FIOASYNC) failed while spawning \"%s\"", name);ngx_close_channel(ngx_processes[s].channel, cycle->log);return NGX_INVALID_PID;}if (fcntl(ngx_processes[s].channel[0], F_SETOWN, ngx_pid) == -1) {ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,"fcntl(F_SETOWN) failed while spawning \"%s\"", name);ngx_close_channel(ngx_processes[s].channel, cycle->log);return NGX_INVALID_PID;}if (fcntl(ngx_processes[s].channel[0], F_SETFD, FD_CLOEXEC) == -1) {ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,"fcntl(FD_CLOEXEC) failed while spawning \"%s\"",name);ngx_close_channel(ngx_processes[s].channel, cycle->log);return NGX_INVALID_PID;}if (fcntl(ngx_processes[s].channel[1], F_SETFD, FD_CLOEXEC) == -1) {ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,"fcntl(FD_CLOEXEC) failed while spawning \"%s\"",name);ngx_close_channel(ngx_processes[s].channel, cycle->log);return NGX_INVALID_PID;}ngx_channel = ngx_processes[s].channel[1];} else {ngx_processes[s].channel[0] = -1;ngx_processes[s].channel[1] = -1;}ngx_process_slot = s;//创建子进程pid = fork();switch (pid) {case -1:ngx_log_error(NGX_LOG_ALERT, cycle->log, ngx_errno,"fork() failed while spawning \"%s\"", name);ngx_close_channel(ngx_processes[s].channel, cycle->log);return NGX_INVALID_PID;case 0:ngx_pid = ngx_getpid();proc(cycle, data);break;default:break;}ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "start %s %P", name, pid);ngx_processes[s].pid = pid;ngx_processes[s].exited = 0;if (respawn >= 0) {return pid;}ngx_processes[s].proc = proc;ngx_processes[s].data = data;ngx_processes[s].name = name;ngx_processes[s].exiting = 0;switch (respawn) {case NGX_PROCESS_NORESPAWN:ngx_processes[s].respawn = 0;ngx_processes[s].just_spawn = 0;ngx_processes[s].detached = 0;break;case NGX_PROCESS_JUST_SPAWN:ngx_processes[s].respawn = 0;ngx_processes[s].just_spawn = 1;ngx_processes[s].detached = 0;break;case NGX_PROCESS_RESPAWN:ngx_processes[s].respawn = 1;ngx_processes[s].just_spawn = 0;ngx_processes[s].detached = 0;break;case NGX_PROCESS_JUST_RESPAWN:ngx_processes[s].respawn = 1;ngx_processes[s].just_spawn = 1;ngx_processes[s].detached = 0;break;case NGX_PROCESS_DETACHED:ngx_processes[s].respawn = 0;ngx_processes[s].just_spawn = 0;ngx_processes[s].detached = 1;break;}if (s == ngx_last_process) {ngx_last_process++;}return pid;
}

static void
ngx_worker_process_cycle(ngx_cycle_t *cycle, void *data)
{ngx_int_t worker = (intptr_t) data;ngx_uint_t         i;ngx_connection_t  *c;ngx_process = NGX_PROCESS_WORKER;//子进程初始化ngx_worker_process_init(cycle, worker);ngx_setproctitle("worker process");//这里有一段多线程条件下的代码。由于nginx并不支持多线程，因此删除掉了//循环for ( ;; ) {//ngx_exiting标志位为1，进程退出if (ngx_exiting) {c = cycle->connections;for (i = 0; i < cycle->connection_n; i++) {if (c[i].fd != -1 && c[i].idle) {c[i].close = 1;c[i].read->handler(c[i].read);}}if (ngx_event_timer_rbtree.root == ngx_event_timer_rbtree.sentinel){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);//处理事件的方法//强制结束进程if (ngx_terminate) {ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "exiting");ngx_worker_process_exit(cycle);}//优雅地退出进程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_close_listening_sockets(cycle);//设置ngx_exiting 标志位ngx_exiting = 1;}}//重新打开所有文件if (ngx_reopen) {ngx_reopen = 0;ngx_log_error(NGX_LOG_NOTICE, cycle->log, 0, "reopening logs");ngx_reopen_files(cycle, -1);}}
}