/* Pthread mutex

* November 21, 2021

* Compile with -lpthread */

#include <pthread.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#define THREADS 4

int counter;

pthread_mutex_t *lock;

static void *handler(void *arg) {

pthread_mutex_lock(lock);

counter++;

printf("Arg = %s\n", arg);

printf("Job %d has started\n", counter);

sleep(2);

printf("Job %d has finished\n", counter);

pthread_mutex_unlock(lock);

pthread_exit(NULL);

return NULL;

}

int main(void) {

int i, error;

pthread_t *tid = (pthread_t *)malloc((sizeof(pthread_t) * THREADS));

lock = (pthread_mutex_t *)malloc(sizeof(pthread_mutex_t));

if (pthread_mutex_init(lock, NULL) != 0) {

fprintf(stderr, "Cannot init mutex\n");

return 1;

}

for (i = 0; i < 4; i++) {

error = pthread_create(&tid[i], NULL, &handler, "hello");

if (error != 0) {

fprintf(stderr, "Thread can't be created: [%s]\n", strerror(error));

}

}

if (error != 0) {

free(lock);

free(tid);

return 1;

}

for (i = 0; i < 4; i++) {

pthread_join(tid[i], NULL);

}

pthread_exit(NULL);

pthread_mutex_destroy(lock);

free(lock);

free(tid);

return 0;

}