grammer/spec.txt

   1 #include <threads.h>
   2 #include <stdlib.h>
   3 #include "librace.h"
   4 #include "model-assert.h"
   5
   6 #include "my_queue.h"
   7
   8 #define relaxed memory_order_relaxed
   9 #define release memory_order_release
  10 #define acquire memory_order_acquire
  11
  12 #define MAX_FREELIST 4 /* Each thread can own up to MAX_FREELIST free nodes */
  13 #define INITIAL_FREE 2 /* Each thread starts with INITIAL_FREE free nodes */
  14
  15 #define POISON_IDX 0x666
  16
  17 static unsigned int (*free_lists)[MAX_FREELIST];
  18
  19 /* Search this thread's free list for a "new" node */
  20 static unsigned int new_node()
  21 {
  22         int i;
  23         int t = get_thread_num();
  24         for (i = 0; i < MAX_FREELIST; i++) {
  25                 unsigned int node = load_32(&free_lists[t][i]);
  26                 if (node) {
  27                         store_32(&free_lists[t][i], 0);
  28                         return node;
  29                 }
  30         }
  31         /* free_list is empty? */
  32         MODEL_ASSERT(0);
  33         return 0;
  34 }
  35
  36 /* Place this node index back on this thread's free list */
  37 static void reclaim(unsigned int node)
  38 {
  39         int i;
  40         int t = get_thread_num();
  41
  42         /* Don't reclaim NULL node */
  43         MODEL_ASSERT(node);
  44
  45         for (i = 0; i < MAX_FREELIST; i++) {
  46                 /* Should never race with our own thread here */
  47                 unsigned int idx = load_32(&free_lists[t][i]);
  48
  49                 /* Found empty spot in free list */
  50                 if (idx == 0) {
  51                         store_32(&free_lists[t][i], node);
  52                         return;
  53                 }
  54         }
  55         /* free list is full? */
  56         MODEL_ASSERT(0);
  57 }
  58
  59 void init_queue(queue_t *q, int num_threads)
  60 {
  61         /**
  62                 @Begin
  63                 @Entry_point
  64                 @End
  65         */
  66
  67         int i, j;
  68
  69         /* Initialize each thread's free list with INITIAL_FREE pointers */
  70         /* The actual nodes are initialized with poison indexes */
  71         free_lists = malloc(num_threads * sizeof(*free_lists));
  72         for (i = 0; i < num_threads; i++) {
  73                 for (j = 0; j < INITIAL_FREE; j++) {
  74                         free_lists[i][j] = 2 + i * MAX_FREELIST + j;
  75                         atomic_init(&q->nodes[free_lists[i][j]].next, MAKE_POINTER(POISON_IDX, 0));
  76                 }
  77         }
  78
  79         /* initialize queue */
  80         atomic_init(&q->head, MAKE_POINTER(1, 0));
  81         atomic_init(&q->tail, MAKE_POINTER(1, 0));
  82         atomic_init(&q->nodes[1].next, MAKE_POINTER(0, 0));
  83 }
  84
  85 /**
  86         @Begin
  87         @Interface_define: Enqueue
  88         @End
  89 */
  90 void enqueue(queue_t *q, unsigned int val)
  91 {
  92         int success = 0;
  93         unsigned int node;
  94         pointer tail;
  95         pointer next;
  96         pointer tmp;
  97
  98         node = new_node();
  99         store_32(&q->nodes[node].value, val);
 100         tmp = atomic_load_explicit(&q->nodes[node].next, relaxed);
 101         set_ptr(&tmp, 0); // NULL
 102         atomic_store_explicit(&q->nodes[node].next, tmp, relaxed);
 103
 104         while (!success) {
 105                 tail = atomic_load_explicit(&q->tail, acquire);
 106                 next = atomic_load_explicit(&q->nodes[get_ptr(tail)].next, acquire);
 107                 if (tail == atomic_load_explicit(&q->tail, 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, release, release);
 116                         }
 117                         if (!success) {
 118                                 unsigned int ptr = get_ptr(atomic_load_explicit(&q->nodes[get_ptr(tail)].next, acquire));
 119                                 pointer value = MAKE_POINTER(ptr,
 120                                                 get_count(tail) + 1);
 121                                 int commit_success = 0;
 122                                 commit_success = atomic_compare_exchange_strong_explicit(&q->tail,
 123                                                 &tail, value, release, release);
 124                                 /**
 125                                         @Begin
 126                                         @Commit_point_define_check: __ATOMIC_RET__ == true
 127                                         @Label: Enqueue_Success_Point
 128                                         @End
 129                                 */
 130                                 thrd_yield();
 131                         }
 132                 }
 133         }
 134         atomic_compare_exchange_strong_explicit(&q->tail,
 135                         &tail,
 136                         MAKE_POINTER(node, get_count(tail) + 1),
 137                         release, release);
 138 }
 139
 140
 141 /**
 142         @Begin
 143         @Interface_define: Dequeue
 144         @End
 145 */
 146 unsigned int dequeue(queue_t *q)
 147 {
 148         unsigned int value;
 149         int success = 0;
 150         pointer head;
 151         pointer tail;
 152         pointer next;
 153
 154         while (!success) {
 155                 head = atomic_load_explicit(&q->head, acquire);
 156                 tail = atomic_load_explicit(&q->tail, relaxed);
 157                 next = atomic_load_explicit(&q->nodes[get_ptr(head)].next, acquire);
 158                 if (atomic_load_explicit(&q->head, relaxed) == head) {
 159                         if (get_ptr(head) == get_ptr(tail)) {
 160
 161                                 /* Check for uninitialized 'next' */
 162                                 MODEL_ASSERT(get_ptr(next) != POISON_IDX);
 163
 164                                 if (get_ptr(next) == 0) { // NULL
 165                                         return 0; // NULL
 166                                 }
 167                                 atomic_compare_exchange_strong_explicit(&q->tail,
 168                                                 &tail,
 169                                                 MAKE_POINTER(get_ptr(next), get_count(tail) + 1),
 170                                                 release, release);
 171                                 thrd_yield();
 172                         } else {
 173                                 value = load_32(&q->nodes[get_ptr(next)].value);
 174                                 success = atomic_compare_exchange_strong_explicit(&q->head,
 175                                                 &head,
 176                                                 MAKE_POINTER(get_ptr(next), get_count(head) + 1),
 177                                                 release, release);
 178                                 /**
 179                                         @Begin
 180                                         @Commit_point_define_check: __ATOMIC_RET__ == true
 181                                         @Label: Dequeue_Success_Point
 182                                         @End
 183                                 */
 184                                 if (!success)
 185                                         thrd_yield();
 186                         }
 187                 }
 188         }
 189         reclaim(get_ptr(head));
 190         return value;
 191 }