Update

lab7/queue.c

@@ -0,0 +1,67 @@
+
+#include <stdlib.h>
+#include "queue.h"
+#include <pthread.h>
+
+/* Remember to initilize the queue before using it */
+void initialize_queue(struct pqueue_t *q)
+{
+	q->head = q->tail = NULL;
+	pthread_mutex_init(&q->lock, NULL);
+}
+
+/* Return non-zero if the queue is empty */
+int empty(struct pqueue_t *q)
+{
+	return (q->head == NULL);
+}
+
+/* Get PCB of a process from the queue (q).
+ * Return NULL if the queue is empty */
+struct pcb_t *de_queue(struct pqueue_t *q)
+{
+	struct pcb_t *proc = NULL;
+	// TODO: return q->head->data and remember to update the queue's head
+	// and tail if necessary. Remember to use 'lock' to avoid race
+	// condition
+
+	// YOUR CODE HERE
+	if (empty(q))
+		return NULL;
+	pthread_mutex_lock(&q->lock);
+	proc = q->head->data;
+	struct qitem_t *pdel = q->head;
+	if (q->head == q->tail)
+		q->head = q->tail = NULL;
+	else
+		q->head = q->head->next;
+	free(pdel);
+	pthread_mutex_unlock(&q->lock);
+
+	return proc;
+}
+
+/* Put PCB of a process to the queue. */
+void en_queue(struct pqueue_t *q, struct pcb_t *proc)
+{
+	// TODO: Update q->tail.
+	// Remember to use 'lock' to avoid race condition
+
+	// YOUR CODE HERE
+	pthread_mutex_lock(&q->lock);
+	struct qitem_t *new_data = malloc(sizeof(struct qitem_t));
+	if (new_data == NULL)
+		return;
+	new_data->data = proc;
+	new_data->next = NULL;
+	if (empty(q))
+	{
+		q->head = q->tail = new_data;
+	}
+	else
+	{
+		q->tail->next = new_data;
+		q->tail = q->tail->next;
+	}
+	pthread_mutex_unlock(&q->lock);
+}