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Unix Threads in C

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Practical example for pthread_mutex_trylock

#include <pthread.h> #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <errno.h> #include <time.h> // chefs = threads // stove = shared data (+mutex) pthread_mutex_t stoveMutex[4]; int stoveFuel[4] = { 100, 100, 100, 100 }; void* routine(void* args) { for (int i = 0; i < 4; i++) { if (pthread_mutex_trylock(&stoveMutex[i]) == 0) { int fuelNeeded = (rand() % 30); if (stoveFuel[i] - fuelNeeded < 0) { printf("No more fuel... going home\n"); } else { stoveFuel[i] -= fuelNeeded; usleep(500000); printf("Fuel left %d\n", stoveFuel[i]); } pthread_mutex_unlock(&stoveMutex[i]); break; } else { if (i == 3) { printf("No stove available yet, waiting...\n"); usleep(300000); i = 0; } } } } int main(int argc, char* argv[]) { srand(time(NULL)); pthread_t th[10]; for (int i = 0; i < 4; i++) { pthread_mutex_init(&stoveMutex[i], NULL); } for (int i = 0; i < 10; i++) { if (pthread_create(&th[i], NULL, &routine, NULL) != 0) { perror("Failed to create thread"); } } for (int i = 0; i < 10; i++) { if (pthread_join(th[i], NULL) != 0) { perror("Failed to join thread"); } } for (int i = 0; i < 4; i++) { pthread_mutex_destroy(&stoveMutex[i]); } return 0; }