#include <threads.h>
#include <stdlib.h>
#include "librace.h"
+#include "model-assert.h"
#include "my_queue.h"
#define release memory_order_release
#define acquire memory_order_acquire
-static unsigned int *node_nums;
+#define MAX_FREELIST 4 /* Each thread can own up to MAX_FREELIST free nodes */
+#define INITIAL_FREE 2 /* Each thread starts with INITIAL_FREE free nodes */
+static unsigned int (*free_lists)[MAX_FREELIST];
+
+/* Search this thread's free list for a "new" node */
static unsigned int new_node()
{
- return node_nums[get_thread_num()];
+ int i;
+ int t = get_thread_num();
+ for (i = 0; i < MAX_FREELIST; i++) {
+ unsigned int node = load_32(&free_lists[t][i]);
+ if (node) {
+ store_32(&free_lists[t][i], 0);
+ return node;
+ }
+ }
+ /* free_list is empty? */
+ MODEL_ASSERT(0);
+ return 0;
}
+/* Place this node index back on this thread's free list */
static void reclaim(unsigned int node)
{
- node_nums[get_thread_num()] = node;
+ int i;
+ int t = get_thread_num();
+
+ /* Don't reclaim NULL node */
+ MODEL_ASSERT(node);
+
+ for (i = 0; i < MAX_FREELIST; i++) {
+ /* Should never race with our own thread here */
+ unsigned int idx = load_32(&free_lists[t][i]);
+
+ /* Found empty spot in free list */
+ if (idx == 0) {
+ store_32(&free_lists[t][i], node);
+ return;
+ }
+ }
+ /* free list is full? */
+ MODEL_ASSERT(0);
}
void init_queue(queue_t *q, int num_threads)
{
- unsigned int i;
- pointer head;
- pointer tail;
- pointer next;
-
- node_nums = malloc(num_threads * sizeof(*node_nums));
- for (i = 0; i < num_threads; i++)
- node_nums[i] = 2 + i;
-
- /* initialize queue */
- head = MAKE_POINTER(1, 0);
- tail = MAKE_POINTER(1, 0);
- next = MAKE_POINTER(0, 0); // (NULL, 0)
-
- atomic_init(&q->head, head);
- atomic_init(&q->tail, tail);
- atomic_init(&q->nodes[1].next, next);
-
- /* initialize avail list */
- for (i = 2; i < MAX_NODES; i++) {
- next = MAKE_POINTER(i + 1, 0);
- atomic_init(&q->nodes[i].next, next);
+ int i, j;
+
+ /* Initialize each thread's free list with INITIAL_FREE NULL "pointers" */
+ free_lists = malloc(num_threads * sizeof(*free_lists));
+ for (i = 0; i < num_threads; i++) {
+ for (j = 0; j < INITIAL_FREE; j++) {
+ free_lists[i][j] = 2 + i * MAX_FREELIST + j;
+ atomic_init(&q->nodes[free_lists[i][j]].next, MAKE_POINTER(0, 0));
+ }
}
- next = MAKE_POINTER(0, 0); // (NULL, 0)
- atomic_init(&q->nodes[MAX_NODES].next, next);
+ /* initialize queue */
+ atomic_init(&q->head, MAKE_POINTER(1, 0));
+ atomic_init(&q->tail, MAKE_POINTER(1, 0));
+ atomic_init(&q->nodes[1].next, MAKE_POINTER(0, 0));
}
void enqueue(queue_t *q, unsigned int val)