--- /dev/null
+#include <threads.h>
+#include <stdlib.h>
+#include "librace.h"
+#include "model-assert.h"
+
+#include "my_queue.h"
+
+#define relaxed memory_order_relaxed
+#define release memory_order_release
+#define acquire memory_order_acquire
+
+#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 */
+
+#define POISON_IDX 0x666
+
+static unsigned int (*free_lists)[MAX_FREELIST];
+
+/* Search this thread's free list for a "new" node */
+static unsigned int new_node()
+{
+ 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)
+{
+ 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)
+{
+ int i, j;
+
+ /* Initialize each thread's free list with INITIAL_FREE pointers */
+ /* The actual nodes are initialized with poison indexes */
+ free_lists = (unsigned (*)[MAX_FREELIST])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(POISON_IDX, 0));
+ }
+ }
+
+ /* 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)
+{
+ int success = 0;
+ unsigned int node;
+ pointer tail;
+ pointer next;
+ pointer tmp;
+
+ node = new_node();
+ store_32(&q->nodes[node].value, val);
+ tmp = atomic_load_explicit(&q->nodes[node].next, relaxed);
+ set_ptr(&tmp, 0); // NULL
+
+ // Bug 1
+ atomic_store_explicit(&q->nodes[node].next, tmp, relaxed);
+ //atomic_store_explicit(&q->nodes[node].next, tmp, release);
+
+ while (!success) {
+ tail = atomic_load_explicit(&q->tail, acquire);
+ next = atomic_load_explicit(&q->nodes[get_ptr(tail)].next, acquire);
+ if (tail == atomic_load_explicit(&q->tail, relaxed)) {
+ /* Check for uninitialized 'next' */
+ MODEL_ASSERT(get_ptr(next) != POISON_IDX);
+
+ if (get_ptr(next) == 0) { // == NULL
+ pointer value = MAKE_POINTER(node, get_count(next) + 1);
+ success = atomic_compare_exchange_strong_explicit(&q->nodes[get_ptr(tail)].next,
+ &next, value, release, release);
+ }
+ if (!success) {
+ unsigned int ptr = get_ptr(atomic_load_explicit(&q->nodes[get_ptr(tail)].next, acquire));
+ pointer value = MAKE_POINTER(ptr,
+ get_count(tail) + 1);
+ atomic_compare_exchange_strong_explicit(&q->tail,
+ &tail, value,
+ release, release);
+ thrd_yield();
+ }
+ }
+ }
+ atomic_compare_exchange_strong_explicit(&q->tail,
+ &tail,
+ MAKE_POINTER(node, get_count(tail) + 1),
+ release, release);
+}
+
+bool dequeue(queue_t *q, unsigned int *retVal)
+{
+ int success = 0;
+ pointer head;
+ pointer tail;
+ pointer next;
+
+ while (!success) {
+ head = atomic_load_explicit(&q->head, acquire);
+
+ // Bug 2
+ tail = atomic_load_explicit(&q->tail, relaxed);
+ //tail = atomic_load_explicit(&q->tail, acquire);
+
+ next = atomic_load_explicit(&q->nodes[get_ptr(head)].next, acquire);
+ if (atomic_load_explicit(&q->head, relaxed) == head) {
+ if (get_ptr(head) == get_ptr(tail)) {
+
+ /* Check for uninitialized 'next' */
+ MODEL_ASSERT(get_ptr(next) != POISON_IDX);
+
+ if (get_ptr(next) == 0) { // NULL
+ return false; // NULL
+ }
+ atomic_compare_exchange_strong_explicit(&q->tail,
+ &tail,
+ MAKE_POINTER(get_ptr(next), get_count(tail) + 1),
+ release, release);
+ thrd_yield();
+ } else {
+ *retVal = load_32(&q->nodes[get_ptr(next)].value);
+ success = atomic_compare_exchange_strong_explicit(&q->head,
+ &head,
+ MAKE_POINTER(get_ptr(next), get_count(head) + 1),
+ release, release);
+ if (!success)
+ thrd_yield();
+ }
+ }
+ }
+ reclaim(get_ptr(head));
+ return true;
+}