mutex.c

#include <stdio.h>
#include <pthread.h>

#define NUM_THREADS 5

// mutex global
pthread_mutex_t mutex;
int global_counter = 0;

void *thread_routine(void *arg) {
  // preluam mutexul global
  pthread_mutex_lock(&mutex);
  // afisam si modificam valoarea variabilei globale 'global_counter'
  printf("Thread %d says global_counter=%d\n", (int) arg, global_counter);
  global_counter ++;

  // eliberam mutexul pentru a acorda acces altui fir de executie
  pthread_mutex_unlock(&mutex);
  return NULL;
}

int main(void) {
  int i;
  pthread_t tids[NUM_THREADS];

  // mutexul este initializat o singura data si folosit de toate firele de executie
  pthread_mutex_init(&mutex, NULL);

  // firele de executie vor executa codul functiei 'thread_routine'
  // in locul unui pointer la date utile, se trimite in ultimul argument
  // un intreg - identificatorul firului de executie
  for (i = 0; i < NUM_THREADS; i++)
    pthread_create(&tids[i], NULL, thread_routine, (void *) i);
  
  // asteptam ca toate firele de executie sa se termine
  for (i = 0; i < NUM_THREADS; i++)
    pthread_join(tids[i], NULL);

  // eliberam resursele mutexului
  pthread_mutex_destroy(&mutex);
  return 0;
}