在父进程恢复执行之前等待所有子进程 UNIX

发布于 2024-08-06 07:04:12 字数 693 浏览 2 评论 0原文

在我的程序中，我在有限的 while 循环中分叉（并行）子进程，并对每个子进程执行 exec 。我希望父进程仅在所有子进程终止后才恢复执行（ while 循环之后的点）。我该怎么做呢？

我尝试了几种方法。在一种方法中，我让父进程在 while 循环后暂停，并仅当 waitpid 返回错误 ECHILD（没有剩余子进程）时从 SIGCHLD 处理程序发送一些条件，但我在这种方法中面临的问题甚至在父进程完成分叉所有进程之前， retStat 变为-1

    void sigchld_handler(int signo) {
        pid_t pid;
        while((pid= waitpid(-1,NULL,WNOHANG)) > 0);
        if(errno == ECHILD) {
            retStat = -1;
        }
    }

    **//parent process code**
    retStat = 1;
    while(some condition) {
       do fork(and exec);
    }

    while(retStat > 0)
        pause();
//This is the point where I want execution to resumed only when all children have finished

原文

In my program I am forking (in parallel) child processes in a finite while loop and doing exec on each of them. I want the parent process to resume execution (the point after this while loop ) only after all children have terminated. How should I do that?

i have tried several approaches. In one approach, I made parent pause after while loop and sent some condition from SIGCHLD handler only when waitpid returned error ECHILD(no child remaining) but the problem I am facing in this approach is even before parent has finished forking all processes, retStat becomes -1

    void sigchld_handler(int signo) {
        pid_t pid;
        while((pid= waitpid(-1,NULL,WNOHANG)) > 0);
        if(errno == ECHILD) {
            retStat = -1;
        }
    }

    **//parent process code**
    retStat = 1;
    while(some condition) {
       do fork(and exec);
    }

    while(retStat > 0)
        pause();
//This is the point where I want execution to resumed only when all children have finished

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小耗子 2024-08-13 07:04:12

与其在信号处理程序中调用 waitpid，为什么不在分叉所有进程后创建一个循环，如下所示：

while (pid = waitpid(-1, NULL, 0)) {
   if (errno == ECHILD) {
      break;
   }
}

程序应该挂在循环中，直到不再有子进程。然后它就会掉下来，程序将继续进行。作为额外的好处，当子进程运行时，循环将在 waitpid 上阻塞，因此您在等待时不需要繁忙的循环。

您还可以使用 wait(NULL) ，它应该相当于 waitpid(-1, NULL, 0)。如果您不需要在SIGCHLD中执行其他操作，则可以将其设置为SIG_DFL。

Instead of calling waitpid in the signal handler, why not create a loop after you have forked all the processes as follows:

while (pid = waitpid(-1, NULL, 0)) {
   if (errno == ECHILD) {
      break;
   }
}

The program should hang in the loop until there are no more children. Then it will fall out and the program will continue. As an additional bonus, the loop will block on waitpid while children are running, so you don't need a busy loop while you wait.

You could also use wait(NULL) which should be equivalent to waitpid(-1, NULL, 0). If there's nothing else you need to do in SIGCHLD, you can set it to SIG_DFL.

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