Sample-Programs-(Synchronization).rar_synchronization

/* Implements the bounded buffer problem There are 4 producers, 1 consumer. */ #include <stdio.h> #include <stdlib.h> #include <pthread.h> #include <semaphore.h> #define NO_OF_SLOTS 8 int Q[NO_OF_SLOTS]; int front = -1; /* Front of the queue */ int rear = -1; /* Rear of the queue */ pthread_mutex_t mutex; /* Mutual exclusion semaphore to gain access to front and rear */ sem_t full; /* # of full slots. Initially 0 */ sem_t empty; /* # of empty slots. Initially NO_OF_SLOTS */ int itemCounter = 0; /* Id of the next item to be inserted to the Queue */ /*---------------------------------------------------- * Producer thread */ void *Producer(void *arg){ int pid; memcpy(&pid, arg, sizeof(int)); printf("Producer <%d> started\n", pid); /* Insert items to queue until itemCounter is 100 */ while (itemCounter < 100){ //sem_wait(&empty); /* Wait until an empty slot opens */ // pthread_mutex_lock(&mutex); /* Get exclusive access to Queue */ itemCounter++; /* Next item to be inserted */ rear = rear + 1; /* Compute the slot where we will insert the next item */ if (rear >= NO_OF_SLOTS) rear = 0; Q[rear] = itemCounter; printf("P<%d> inserted item <%4d> into the Q\n", pid, itemCounter); // pthread_mutex_unlock(&mutex); /* Done inserting item to the queue */ //sem_post(&full); /* Notify consumer: One more full slot in the Queue */ } /* end-while */ } /* end-Producer */ /*---------------------------------------------------- * Consumer thread */ void *Consumer(void *arg){ int item = 0; printf("Consumer started\n"); while (item < 100){ // sem_wait(&full); /* Wait until a slot is full */ //pthread_mutex_lock(&mutex); /* Get exclusive access to Queue */ front = front + 1; /* Compute the slot where the next item resides */ if (front >= NO_OF_SLOTS) front = 0; item = Q[front]; printf("Removed item <%4d> from the Q\n", item); //pthread_mutex_unlock(&mutex); /* Done removing item from the Q */ //sem_post(&empty); /* Notify producers: One more empty slot in the Queue */ } /* end-while */ } /* end-Consumer */ /*------------------------------------------- * Main */ int main(int argc,char *argv[]){ int i, j; pthread_t producerIds[4]; pthread_t consumerId; int ids[4] = {1, 2, 3, 4}; pthread_mutex_init(&mutex,NULL); sem_init(&full, 0, 0); /* No slots are full at the beginning */ sem_init(&empty, 0, NO_OF_SLOTS); /* All slots are empty at the beginning */ /* Create 1 consumer thread */ pthread_create(&consumerId, NULL, Consumer, NULL); /* Create 4 producers */ for(i=0;i<4;i++) pthread_create(&producerIds[i], NULL, Producer, &ids[i]); /* Wait until the threads are done. */ pthread_join(consumerId, NULL); for(i=0;i<4;i++)pthread_join(producerIds[i], NULL); return 0; } /* end-main */