4 #include "model-assert.h"
9 #define MAX_FREELIST 4 /* Each thread can own up to MAX_FREELIST free nodes */
10 #define INITIAL_FREE 2 /* Each thread starts with INITIAL_FREE free nodes */
12 #define POISON_IDX 0x666
14 static unsigned int (*free_lists)[MAX_FREELIST];
16 /* Search this thread's free list for a "new" node */
17 static unsigned int new_node()
20 int t = get_thread_num();
21 for (i = 0; i < MAX_FREELIST; i++) {
22 //unsigned int node = load_32(&free_lists[t][i]);
23 unsigned int node = free_lists[t][i];
25 //store_32(&free_lists[t][i], 0);
30 /* free_list is empty? */
35 /* Simulate the fact that when a node got recycled, it will get assigned to the
36 * same queue or for other usage */
37 void simulateRecycledNodeUpdate(queue_t *q, unsigned int node) {
38 atomic_store_explicit(&q->nodes[node].next, -1, memory_order_release);
41 /* Place this node index back on this thread's free list */
42 static void reclaim(unsigned int node)
45 int t = get_thread_num();
47 /* Don't reclaim NULL node */
50 for (i = 0; i < MAX_FREELIST; i++) {
51 /* Should never race with our own thread here */
52 //unsigned int idx = load_32(&free_lists[t][i]);
53 unsigned int idx = free_lists[t][i];
55 /* Found empty spot in free list */
57 //store_32(&free_lists[t][i], node);
58 free_lists[t][i] = node;
62 /* free list is full? */
66 void init_queue(queue_t *q, int num_threads)
70 /* Initialize each thread's free list with INITIAL_FREE pointers */
71 /* The actual nodes are initialized with poison indexes */
72 free_lists = malloc(num_threads * sizeof(*free_lists));
73 for (i = 0; i < num_threads; i++) {
74 for (j = 0; j < INITIAL_FREE; j++) {
75 free_lists[i][j] = 2 + i * MAX_FREELIST + j;
76 atomic_init(&q->nodes[free_lists[i][j]].next, MAKE_POINTER(POISON_IDX, 0));
80 /* initialize queue */
81 atomic_init(&q->head, MAKE_POINTER(1, 0));
82 atomic_init(&q->tail, MAKE_POINTER(1, 0));
83 atomic_init(&q->nodes[1].next, MAKE_POINTER(0, 0));
86 void enqueue(queue_t *q, unsigned int val, bool yield)
95 //store_32(&q->nodes[node].value, val);
96 q->nodes[node].value = val;
97 tmp = atomic_load_explicit(&q->nodes[node].next, wildcard(1)); // relaxed
98 set_ptr(&tmp, 0); // NULL
99 atomic_store_explicit(&q->nodes[node].next, tmp, wildcard(2)); // relaxed
102 tail = atomic_load_explicit(&q->tail, wildcard(3)); // acquire
103 // FIXME: SCFence makes this relaxed
106 next = atomic_load_explicit(&q->nodes[get_ptr(tail)].next, wildcard(4)); //acquire
107 if (tail == atomic_load_explicit(&q->tail, wildcard(5))) { // relaxed
109 /* Check for uninitialized 'next' */
110 //MODEL_ASSERT(get_ptr(next) != POISON_IDX);
112 if (get_ptr(next) == 0) { // == NULL
113 pointer value = MAKE_POINTER(node, get_count(next) + 1);
114 success = atomic_compare_exchange_strong_explicit(&q->nodes[get_ptr(tail)].next,
115 &next, value, wildcard(6), wildcard(7)); // release & relaxed
119 get_ptr(atomic_load_explicit(&q->nodes[get_ptr(tail)].next, wildcard(8))); // acquire
120 pointer value = MAKE_POINTER(ptr,
121 get_count(tail) + 1);
122 atomic_compare_exchange_strong_explicit(&q->tail,
124 wildcard(9), wildcard(10)); // release & relaxed
129 atomic_compare_exchange_strong_explicit(&q->tail,
131 MAKE_POINTER(node, get_count(tail) + 1),
132 wildcard(11), wildcard(12)); // release & relaxed
135 bool dequeue(queue_t *q, unsigned int *retVal, unsigned int *reclaimNode)
144 head = atomic_load_explicit(&q->head, wildcard(13)); // acquire
145 // SCFence makes this acquire, and we actually need an acquire here!!!
146 tail = atomic_load_explicit(&q->tail, wildcard(14)); // relaxed
147 next = atomic_load_explicit(&q->nodes[get_ptr(head)].next, wildcard(15)); // acquire
148 if (atomic_load_explicit(&q->head, wildcard(16)) == head) { // relaxed
149 if (get_ptr(head) == get_ptr(tail)) {
151 /* Check for uninitialized 'next' */
152 //MODEL_ASSERT(get_ptr(next) != POISON_IDX);
154 if (get_ptr(next) == 0) { // NULL
155 return false; // NULL
157 atomic_compare_exchange_strong_explicit(&q->tail,
159 MAKE_POINTER(get_ptr(next), get_count(tail) + 1),
160 wildcard(17), wildcard(18)); // release & relaxed
163 //value = load_32(&q->nodes[get_ptr(next)].value);
164 value = q->nodes[get_ptr(next)].value;
165 success = atomic_compare_exchange_strong_explicit(&q->head,
166 &head, MAKE_POINTER(get_ptr(next), get_count(head) + 1),
167 wildcard(19), wildcard(20)); // release & relaxed
174 reclaimNode = get_ptr(head);
175 reclaim(get_ptr(head));