I find it difficult to understand IPC in a multiprocessor system. I have this system in which there are three child processes that send two types of signals to their process group. There are four types of signal processing processes that are responsible for a particular type of signal.
There is such a monitoring process that waits for both signals and then processes accordingly. When I run this program for a while, the monitoring process does not seem to perceive the signal, as well as the signal processing process. I could see in the log that the signal was generated, but not processed at all.
My code is below
#include <cstdlib> #include <iostream> #include <iomanip> #include <unistd.h> #include <sys/types.h> #include <sys/wait.h> #include <sys/time.h> #include <signal.h> #include <unistd.h> #include <fcntl.h> #include <cstdio> #include <stdlib.h> #include <stdio.h> #include <pthread.h> using namespace std; double timestamp() { struct timeval tp; gettimeofday(&tp, NULL); return (double)tp.tv_sec + tp.tv_usec / 1000000.; } double getinterval() { srand(time(NULL)); int r = rand()%10 + 1; double s = (double)r/100; } int count; int count_1; int count_2; double time_1[10]; double time_2[10]; pid_t senders[1]; pid_t handlers[4]; pid_t reporter; void catcher(int sig) { printf("Signal catcher called for %d",sig); } int main(int argc, char *argv[]) { void signal_catcher_int(int); pid_t pid,w; int status; if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("1"); return 1; } if(signal(SIGUSR2 ,SIG_IGN) == SIG_ERR) { perror("2"); return 2; } if(signal(SIGINT,signal_catcher_int) == SIG_ERR) { perror("3"); return 2; } //Registering the signal handler for(int i=0; i<4; i++) { if((pid = fork()) == 0) { cout << i << endl; //struct sigaction sigact; sigset_t sigset; int sig; int result = 0; sigemptyset(&sigset); if(i%2 == 0) { if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); return 2; } sigaddset(&sigset, SIGUSR1); sigprocmask(SIG_BLOCK, &sigset, NULL); } else { if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("2"); return 2; } sigaddset(&sigset, SIGUSR2); sigprocmask(SIG_BLOCK, &sigset, NULL); } while(true) { int result = sigwait(&sigset, &sig); if(result == 0) { cout << "The caught signal is " << sig << endl; } } exit(0); } else { cout << "Registerd the handler " << pid << endl; handlers[i] = pid; } } //Registering the monitoring process if((pid = fork()) == 0) { sigset_t sigset; int sig; int result = 0; sigemptyset(&sigset); sigaddset(&sigset, SIGUSR1); sigaddset(&sigset, SIGUSR2); sigprocmask(SIG_BLOCK, &sigset, NULL); while(true) { int result = sigwait(&sigset, &sig); if(result == 0) { cout << "The monitored signal is " << sig << endl; } else { cout << "error" << endl; } } } else { reporter = pid; } sleep(3); //Registering the signal generator for(int i=0; i<1; i++) { if((pid = fork()) == 0) { if(signal(SIGUSR1, SIG_IGN) == SIG_ERR) { perror("1"); return 1; } if(signal(SIGUSR2, SIG_IGN) == SIG_ERR) { perror("2"); return 2; } srand(time(0)); while(true) { volatile int signal_id = rand()%2 + 1; cout << "Generating the signal " << signal_id << endl; if(signal_id == 1) { killpg(getpgid(getpid()), SIGUSR1); } else { killpg(getpgid(getpid()), SIGUSR2); } int r = rand()%10 + 1; double s = (double)r/100; sleep(s); } exit(0); } else { cout << "Registered the sender " << pid << endl; senders[i] = pid; } } while(w = wait(&status)) { cout << "Wait on PID " << w << endl; } } void signal_catcher_int(int the_sig) { //cout << "Handling the Ctrl C signal " << endl; for(int i=0; i<1; i++) { kill(senders[i],SIGKILL); } for(int i=0; i<4; i++) { kill(handlers[i],SIGKILL); } kill(reporter,SIGKILL); exit(3); }
Any suggestions?
Here is an example output file
At the beginning
Registerd the handler 9544 Registerd the handler 9545 1 Registerd the handler 9546 Registerd the handler 9547 2 3 0 Registered the sender 9550 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 1 The caught signal is 10 The monitored signal is 10 The caught signal is 10 Generating the signal 2 The caught signal is 12 The caught signal is 12 The monitored signal is 12 Generating the signal 2 Generating the signal 2 The caught signal is 12 The caught signal is 12 Generating the signal 1 The caught signal is 12 The monitored signal is 10 The monitored signal is 12 Generating the signal 1 Generating the signal 2 The caught signal is 12 Generating the signal 1 Generating the signal 2 10 The monitored signal is 10 The caught signal is 12 Generating the signal 1 The caught signal is 12 The monitored signal is GenThe caught signal is TheThe caught signal is 10 Generating the signal 2
Later
The monitored signal is GenThe monitored signal is 10 Generating the signal 1 Generating the signal 2 The caught signal is 10 The caught signal is 10 The caught signal is 10 The caught signal is 12 Generating the signal 1 Generating the signal 2 Generating the signal 1 Generating the signal 1 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 1 The caught signal is 12 The caught signal is 10 The caught signal is 10 Generating the signal 2 Generating the signal 1 Generating the signal 1 Generating the signal 2 Generating the signal 1 Generating the signal 2 Generating the signal 2 Generating the signal 2 Generating the signal 1 Generating the signal 2 Generating the signal 1 Generating the signal 2 Generating the signal 2 The caught signal is 10 Generating the signal 2 Generating the signal 1 Generating the signal 1
As you can see from the beginning, the signal was generated and processed by both my signal handlers and the monitoring processes. But later the signal was generated a lot, but these were not quite processes in the same magnitude as before. In addition, I could see that the signal processing process is much smaller
Maybe someone can give some ideas. What's happening?