Process Synchronization (Fork) - "segmentation fault"

Question

Process Synchronization (Fork) - "segmentation fault"

Navigation

#1 by (1 votes)

1

I'm trying to create 3 processes and use semaphore in them. The code below compiles, but in the middle of the execution there is an error called "segmentation fault". I do not know how to solve this. Thank you for your patience. The goal is to create a semaphore that could be shared by processes.

#include <pthread.h>
#include <semaphore.h>
#include <sys/sem.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <semaphore.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/wait.h>


void F1(){
                 printf("F1\n");
                sem_t *sem;
                sem = sem_open("mysem", O_CREAT, 0600, 0);
                sem_init(sem,1,1);
                for(;;){
                        sem_wait(sem);
                        printf("Filosofo 1 - Vou executar 10 segundos\n");
                        sleep(10);
                        sem_post(sem);
                }

}

void F2(){
                 printf("F2\n");
                sem_t *sem;
                sem = sem_open("mysem", O_CREAT, 0600, 0);
                sem_init(sem,1,1);
                for(;;){
                        sem_wait(sem);
                        printf("Filosofo 2 - Vou executar 10 segundos\n");
                        sleep(10);
                        sem_post(sem);
                }

}

void F3(){
 printf("F3\n");
                 printf("F3\n");
                sem_t *sem;
                sem = sem_open("mysem", O_CREAT, 0600, 0);
                sem_init(sem,1,1);
                for(;;){
                        sem_wait(sem);
                        printf("Filosofo 3 - Vou executar 10 segundos\n");
                        sleep(10);
                        sem_post(sem);
                }

}



int main(int arc, char *argv[]){
    int i, n=3;

    for(i=0; i<n; i++) {
        if(i == 0){
                 printf("Fui executado i vez\n",i);
        }
        if(fork())
                break;
    }

    switch(i) {
        case 0:
            F1();
            break;

        case 1:
            F2();
            break;

        case 2:
            F3();
            break;
    }
}

c linux

asked by anonymous 07.06.2014 / 18:36

1 answer

Retrieve parameter sent to a modal and perform MySQL query Protect pages that are loaded inside the template - Kohana

score 1 · Answer 1

Well I discovered a small code error and you need to include it in the -lpthread compilation, so the command would be in the ($ gcc NOMEDOARQUIVO.c -lpthread) terminal. Here is corrected code:

#include <pthread.h>
#include <semaphore.h>
#include <sys/sem.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <semaphore.h>
#include <errno.h>
#include <fcntl.h>
#include <sys/wait.h>

void f1(void);
void f2(void);
void f3(void);


void f1(void){
      printf("F1\n");
      sem_t *sem;
      sem = sem_open("mysem", O_CREAT, 0600, 0);
      sem_init(sem,1,1);
      for(;;){
          sem_wait(sem);
          printf("Filosofo 1 - Vou executar 10 segundos\n");
          sleep(10);
          sem_post(sem);
       }

}
void f2(void){
    printf("F2\n");
    sem_t *sem;
    sem = sem_open("mysem", O_CREAT, 0600, 0);
    sem_init(sem,1,1);
    for(;;){
        sem_wait(sem);
        printf("Filosofo 2 - Vou executar 10 segundos\n");
        sleep(10);
        sem_post(sem);
    }

}
void f3(void){
    printf("F3\n");
    printf("F3\n");
    sem_t *sem;
    sem = sem_open("mysem", O_CREAT, 0600, 0);
    sem_init(sem,1,1);
    for(;;){
        sem_wait(sem);
        printf("Filosofo 3 - Vou executar 10 segundos\n");
        sleep(10);
        sem_post(sem);
    }

}
int main(int arc, char *argv[]){
    int i, n=3;

    for(i=0; i<n; i++) {
        if(i == 0){
            printf("Fui executado %i vez\n",i); //Faltou o % do lado do i
        }
        if(fork()){
            break;
        }
    }    
    switch(i) {
        case 0:
            f1();
            break;

        case 1:
            f2();
            break;

        case 2:
            f3();
            break;
    }

}

//Para compilar execute
// $ gcc NOMEDOARQUIVO.c -lpthread
//FUNCIONOU CERTINHO