Linux中使用sigaction的信号处理程序（C ++）

Question

I am trying to send SIGUSR1/SIGUSR2 signals between multiple processes using custom handler, but my handler does not work. It is not printing any debug messages or anything.

Here I am creating 8 processes and trying to set a custom handler using set_sigaction function:

int main(){
    pidArray = (int *)mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE,MAP_ANONYMOUS | MAP_SHARED, -1, 0);//Self pid
    pidArray2 = (int *)mmap(NULL, MMAP_SIZE, PROT_READ | PROT_WRITE,MAP_ANONYMOUS | MAP_SHARED, -1, 0);//Child pid
    counter = (int *)mmap(NULL, MMAP_SIZE2, PROT_READ | PROT_WRITE,MAP_ANONYMOUS | MAP_SHARED, -1, 0);
    counter[0]=0;
    counter[1]=0;
    pid_t pid, pid2;
    int counter = 1;
    pidArray[0]=getpid();
    pid = fork(); //1
    if(pid == 0){
        pid = fork(); //2
        if(pid != 0){
            pidArray[1]=getpid();
            pidArray2[1]=pid;
        }
        if(pid == 0){
            pid2 = getpid();
            pidArray[2]=pid2;
            pid=fork(); //4
            if(pid == 0){
                pidArray[4] = getpid();
                pid=fork(); //5
                if(pid==0){
                    pidArray[5] = getpid();
                    pidArray2[5] = 0;
                }
                else
                    pidArray2[4] = pid;
            }
        if(pid2 == getpid()){
            pid2 = fork(); //3
            if(pid2!=0){
                pid = setpgid(pid,pid2);
            }
            else{
                pidArray[3]=getpid();
                pid=fork(); //6
                if(pid==0){
                    pidArray[6]=getpid();
                    pid=fork(); //7
                    if(pid==0){
                        pidArray[7]=getpid();
                        pid=fork(); //8
                        if(pid!=0)
                            pidArray2[7]=pid;
                        else{
                            pidArray[8]=getpid();
                            pidArray2[8]=pidArray[1];
                        }

                    }
                    else
                        pidArray2[6]=pid;
                }
                else
                    pidArray2[3]=pid;
            }
        }        
        }
    }

    set_sigaction(SIGUSR1);

    sleep(5);

    if(getpid()==pidArray[1])
        kill(pidArray[0],SIGTERM);
    if(getpid()==pidArray[1]){
        send_signal(pidArray[1]);
    }
    sleep(100);
    return 0; 

Here is set_sigaction function:

static int set_sigaction(int signo) 
{ 
    struct sigaction sa; 
    memset(&sa, 0, sizeof(struct sigaction));
    sa.sa_sigaction = handler;
    sigemptyset(&sa.sa_mask);  
    sa.sa_flags = SA_SIGINFO;
    return sigaction(signo, &sa, NULL);
}

And here is the handler:

static void handler(int signo, siginfo_t* si, void* ucontext){
    int k;
    int i;
    pid_t pid = getpid();
    for(i=1;i<9;i++){
        if(pidArray[i]==pid)
            k=i;
    }
    time_t rawtime;
    time ( &rawtime );
    cout << k << " " << pid << " Got USR1 " << ctime (&rawtime) << "\n";
    send_signal(getpid());
}

My send_signal function gives me this message, which means it send SIGUSR1 signal to the second process:

1 3156 Send USR1 Thu Jun 22 18:04:54 2017

I am thinking the problem is how I create multiple processes or how i set my handler.

Answer 1

what does send_signal do ? Try sending the signal using the kill function as :

kill(pidArray[1], SIGUSR1)