到目前为止,没有任何解决方案提供了一种不使用SIGCHLD作为问题请求的方法。这是因为在this answer概述使用poll另一种方法的实现(这也解释了为什么你应该避免使用在这样的情况下SIGCHLD):
确保您从您创建的每个子进程有一个管/ 。它可以是他们的stdin/stdout/stderr或者只是一个额外的虚拟fd。当子进程终止时,管道的末端将被关闭,并且主事件循环将检测该文件描述符上的活动。从它关闭的事实中,你认识到子进程已经死亡,并且调用waitpid来获得僵尸。
(注意:我省略了一些最佳实践,如错误检查和清理为了简洁文件描述符)
/**
* Specifies the maximum number of clients to keep track of.
*/
#define MAX_CLIENT_COUNT 1000
/**
* Tracks clients by storing their process IDs and pipe file descriptors.
*/
struct process_table {
pid_t clientpids[MAX_CLIENT_COUNT];
struct pollfd clientfds[MAX_CLIENT_COUNT];
} PT;
/**
* Initializes the process table. -1 means the entry in the table is available.
*/
void initialize_table() {
for (int i = 0; i < MAX_CLIENT_COUNT; i++) {
PT.clientfds[i].fd = -1;
}
}
/**
* Returns the index of the next available entry in the process table.
*/
int get_next_available_entry() {
for (int i = 0; i < MAX_CLIENT_COUNT; i++) {
if (PT.clientfds[i].fd == -1) {
return i;
}
}
return -1;
}
/**
* Adds information about a new client to the process table.
*/
void add_process_to_table(int i, pid_t pid, int fd) {
PT.clientpids[i] = pid;
PT.clientfds[i].fd = fd;
}
/**
* Removes information about a client from the process table.
*/
void remove_process_from_table(int i) {
PT.clientfds[i].fd = -1;
}
/**
* Cleans up any dead child processes from the process table.
*/
void reap_zombie_processes() {
int p = poll(PT.clientfds, MAX_CLIENT_COUNT, 0);
if (p > 0) {
for (int i = 0; i < MAX_CLIENT_COUNT; i++) {
/* Has the pipe closed? */
if ((PT.clientfds[i].revents & POLLHUP) != 0) {
// printf("[%d] done\n", PT.clientpids[i]);
waitpid(PT.clientpids[i], NULL, 0);
remove_process_from_table(i);
}
}
}
}
/**
* Simulates waiting for a new client to connect.
*/
void accept() {
sleep((rand() % 4) + 1);
}
/**
* Simulates useful work being done by the child process, then exiting.
*/
void childfunction() {
sleep((rand() % 10) + 1);
exit(0);
}
/**
* Main program
*/
int main() {
/* Initialize the process table */
initialize_table();
while (1) {
accept();
/* Create the pipe */
int p[2];
pipe(p);
/* Fork off a child process. */
pid_t cpid = fork();
if (cpid == 0) {
/* Child process */
close(p[0]);
childfunction();
}
else {
/* Parent process */
close(p[1]);
int i = get_next_available_entry();
add_process_to_table(i, cpid, p[0]);
// printf("[%d] started\n", cpid);
reap_zombie_processes();
}
}
return 0;
}
这里是从与printf
语句注释掉运行该程序的一些示例输出:
[31066] started
[31067] started
[31068] started
[31069] started
[31066] done
[31070] started
[31067] done
[31068] done
[31071] started
[31069] done
[31072] started
[31070] done
[31073] started
[31074] started
[31072] done
[31075] started
[31071] done
[31074] done
[31081] started
[31075] done
你可以在SIGCHLD – tristan 2010-03-04 08:40:49
的信号处理程序中做些什么我已经提到过... SIGCHLD信号被忽略..? – codingfreak 2010-03-04 08:45:45
+1的疯狂戏剧题目和开头句子。 D: – 2010-03-04 09:22:48