Geek asks and answers

How can I be sure that I do not lose signals when using pause ()?

I am writing a program that uses fork to create child processes and counts them when they are done. How can I be sure that I will not lose signals? What happens if a child sends a signal while the main program is still processing the previous signal? lost signal? how can i avoid this situation?

void my_prog()
{
    for(i = 0; i<numberOfDirectChildrenGlobal; ++i) {    
        pid = fork();
        if(pid > 0)//parent
            //do parent thing
        else if(0 == pid) //child
            //do child thing
        else
            //exit with error
    }

    while(numberOfDirectChildrenGlobal > 0) {
        pause(); //waiting for signal as many times as number of direct children
    }

    kill(getppid(),SIGUSR1);
    exit(0);
}

void sigUsrHandler(int signum)
{
    //re-register to SIGUSR1
    signal(SIGUSR1, sigUsrHandler);
    //update number of children that finished
    --numberOfDirectChildrenGlobal;
}
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3 answers

sigaction , , . , , , , ( , , ). .

, , , .

. , SIGCHLD , . waitpid WNOHANG , , .

, SIGCHLD, , :

 pid_t pid;

 while((pid = waitpid(-1, NULL, WNOHANG)) > 0) {
       nrOfChildrenHandled++;
 }
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sigaction , .

0

To avoid this situation, you can use posix signals.

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