a multi-threaded producer / consumer program without any locking or signaling. It therefore has synchronization problems. Add locks and signals so that it works correctly. /* Homework 5.X */ /* Robin Ehrlich */

/* compile: gcc Homework5.c -lpthread */

#include #include #include #include

struct class { struct class *next; int id; int grade; };

#define SLEEP_TIME 1 #define MAX_PRODUCE 10

static struct class *classHead = NULL; static struct class *classTail = NULL; static pthread_mutex_t classMutex; static pthread_cond_t classSignal; static int producerComplete = 0; static int randomSeed;

static void *consumerThread(void *arg) {

struct class *classCurrent; int sleepTime;

printf("Consumer thread starting ");

while (1) {

/* get next item */ classCurrent = classHead; if ((classCurrent == NULL) && (producerComplete)) break; classHead = classCurrent->next;

/* do some work */ printf("consume: id = %d, grade = %d ", classCurrent->id, classCurrent->grade); sleepTime = (rand_r(&randomSeed) % SLEEP_TIME) + 1; sleep(sleepTime); free(classCurrent); }

printf("Consumer thread completed ");

return (0);

}

static void *producerThread(void *arg) { struct class *classCurrent; int i; int sleepTime;

printf("Producer thread starting ");

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

/* do some work */ printf("produce: id = %d, grade = %d ", classCurrent->id, classCurrent->grade); sleepTime = (rand_r(&randomSeed) % SLEEP_TIME) + 1; sleep(sleepTime);

/* give to consumer */

classCurrent = malloc(sizeof(struct class)); classCurrent->id = 462 + i; classCurrent->grade = 90 - i; classCurrent->next = NULL; if (classHead == NULL) classHead = classCurrent; else classTail->next = classCurrent; classTail = classCurrent; }

producerComplete = 1;

printf("Producer thread completed ");

return (0);

}

int main(int argc, char **argv) {

pthread_attr_t attr; struct class *classCurrent; pthread_t consumerTid; pthread_t producerTid;

printf("Starting ");

randomSeed = (int) time(NULL); srand(randomSeed);

pthread_mutex_init(&classMutex, NULL); pthread_cond_init(&classSignal, NULL);

pthread_attr_init(&attr); pthread_create(&producerTid, &attr, producerThread, NULL); pthread_create(&consumerTid, &attr, consumerThread, NULL);

/* wait for threads to complete */

pthread_join(producerTid, NULL); pthread_join(consumerTid, NULL);

printf("Completed ");

return (0);

}