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Unix Threads in C

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Signaling for condition variables (pthread_cond_signal vs pthread_cond_broadcast)

#include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> pthread_mutex_t mutexFuel; pthread_cond_t condFuel; int fuel = 0; void* fuel_filling(void* arg) { for (int i = 0; i < 5; i++) { pthread_mutex_lock(&mutexFuel); fuel += 30; printf("Filled fuel... %d\n", fuel); pthread_mutex_unlock(&mutexFuel); pthread_cond_broadcast(&condFuel); sleep(1); } } void* car(void* arg) { pthread_mutex_lock(&mutexFuel); while (fuel < 40) { printf("No fuel. Waiting...\n"); pthread_cond_wait(&condFuel, &mutexFuel); // Equivalent to: // pthread_mutex_unlock(&mutexFuel); // wait for signal on condFuel // pthread_mutex_lock(&mutexFuel); } fuel -= 40; printf("Got fuel. Now left: %d\n", fuel); pthread_mutex_unlock(&mutexFuel); } int main(int argc, char* argv[]) { pthread_t th[6]; pthread_mutex_init(&mutexFuel, NULL); pthread_cond_init(&condFuel, NULL); for (int i = 0; i < 6; i++) { if (i == 4 || i == 5) { if (pthread_create(&th[i], NULL, &fuel_filling, NULL) != 0) { perror("Failed to create thread"); } } else { if (pthread_create(&th[i], NULL, &car, NULL) != 0) { perror("Failed to create thread"); } } } for (int i = 0; i < 6; i++) { if (pthread_join(th[i], NULL) != 0) { perror("Failed to join thread"); } } pthread_mutex_destroy(&mutexFuel); pthread_cond_destroy(&condFuel); return 0; }