ms-queue/queue_wildcard.c

   1 #include <threads.h>
   2 #include <stdlib.h>
   3 #include "librace.h"
   4 #include "model-assert.h"
   5
   6 #include "queue.h"
   7 #include "wildcard.h"
   8
   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 */
  11
  12 #define POISON_IDX 0x666
  13
  14 static unsigned int (*free_lists)[MAX_FREELIST];
  15
  16 /* Search this thread's free list for a "new" node */
  17 static unsigned int new_node()
  18 {
  19         int i;
  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];
  24                 if (node) {
  25                         //store_32(&free_lists[t][i], 0);
  26                         free_lists[t][i] = 0;
  27                         return node;
  28                 }
  29         }
  30         /* free_list is empty? */
  31         MODEL_ASSERT(0);
  32         return 0;
  33 }
  34
  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);
  39 }
  40
  41 /* Place this node index back on this thread's free list */
  42 static void reclaim(unsigned int node)
  43 {
  44         int i;
  45         int t = get_thread_num();
  46
  47         /* Don't reclaim NULL node */
  48         //MODEL_ASSERT(node);
  49
  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];
  54
  55                 /* Found empty spot in free list */
  56                 if (idx == 0) {
  57                         //store_32(&free_lists[t][i], node);
  58                         free_lists[t][i] = node;
  59                         return;
  60                 }
  61         }
  62         /* free list is full? */
  63         MODEL_ASSERT(0);
  64 }
  65
  66 void init_queue(queue_t *q, int num_threads)
  67 {
  68         int i, j;
  69
  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));
  77                 }
  78         }
  79
  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));
  84 }
  85
  86 void enqueue(queue_t *q, unsigned int val, bool yield)
  87 {
  88         int success = 0;
  89         unsigned int node;
  90         pointer tail;
  91         pointer next;
  92         pointer tmp;
  93
  94         node = new_node();
  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
 100
 101         while (!success) {
 102                 tail = atomic_load_explicit(&q->tail, wildcard(3)); // acquire
 103                 // FIXME: SCFence makes this relaxed
 104                 if (yield)
 105                         thrd_yield();
 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
 108
 109                         /* Check for uninitialized 'next' */
 110                         //MODEL_ASSERT(get_ptr(next) != POISON_IDX);
 111
 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
 116                         }
 117                         if (!success) {
 118                                 unsigned int ptr =
 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,
 123                                                 &tail, value,
 124                                                 wildcard(9), wildcard(10)); // release & relaxed
 125                                 thrd_yield();
 126                         }
 127                 }
 128         }
 129         atomic_compare_exchange_strong_explicit(&q->tail,
 130                         &tail,
 131                         MAKE_POINTER(node, get_count(tail) + 1),
 132                         wildcard(11), wildcard(12)); // release & relaxed
 133 }
 134
 135 bool dequeue(queue_t *q, unsigned int *retVal, unsigned int *reclaimNode)
 136 {
 137         unsigned int value;
 138         int success = 0;
 139         pointer head;
 140         pointer tail;
 141         pointer next;
 142
 143         while (!success) {
 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)) {
 150
 151                                 /* Check for uninitialized 'next' */
 152                                 //MODEL_ASSERT(get_ptr(next) != POISON_IDX);
 153
 154                                 if (get_ptr(next) == 0) { // NULL
 155                                         return false; // NULL
 156                                 }
 157                                 atomic_compare_exchange_strong_explicit(&q->tail,
 158                                                 &tail,
 159                                                 MAKE_POINTER(get_ptr(next), get_count(tail) + 1),
 160                                                 wildcard(17), wildcard(18)); // release & relaxed
 161                                 thrd_yield();
 162                         } else {
 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
 168                                 if (!success)
 169                                         thrd_yield();
 170                         }
 171                 }
 172         }
 173
 174         reclaimNode = get_ptr(head);
 175         reclaim(get_ptr(head));
 176         *retVal = value;
 177         return true;
 178 }