ms-queue/my_queue.c

   1 #include <threads.h>
   2 #include <stdlib.h>
   3 #include "librace.h"
   4
   5 #include "my_queue.h"
   6
   7 static unsigned int *node_nums;
   8
   9 static unsigned int new_node()
  10 {
  11         return node_nums[get_thread_num()];
  12 }
  13
  14 static void reclaim(unsigned int node)
  15 {
  16         node_nums[get_thread_num()] = node;
  17 }
  18
  19 void init_queue(queue_t *q, int num_threads)
  20 {
  21         unsigned int i;
  22         pointer head;
  23         pointer tail;
  24         pointer next;
  25
  26         node_nums = malloc(num_threads * sizeof(*node_nums));
  27         for (i = 0; i < num_threads; i++)
  28                 node_nums[i] = 2 + i;
  29
  30         /* Note: needed to add this init manually */
  31         atomic_init(&q->nodes[0].next, 0);
  32
  33         /* initialize queue */
  34         head = MAKE_POINTER(1, 0);
  35         tail = MAKE_POINTER(1, 0);
  36         next = MAKE_POINTER(0, 0); // (NULL, 0)
  37
  38         atomic_init(&q->head, head);
  39         atomic_init(&q->tail, tail);
  40         atomic_init(&q->nodes[1].next, next);
  41
  42         /* initialize avail list */
  43         for (i = 2; i < MAX_NODES; i++) {
  44                 next = MAKE_POINTER(i + 1, 0);
  45                 atomic_init(&q->nodes[i].next, next);
  46         }
  47
  48         next = MAKE_POINTER(0, 0); // (NULL, 0)
  49         atomic_init(&q->nodes[MAX_NODES].next, next);
  50 }
  51
  52 void enqueue(queue_t *q, unsigned int val)
  53 {
  54         int success = 0;
  55         unsigned int node;
  56         pointer tail;
  57         pointer next;
  58         pointer tmp;
  59
  60         node = new_node();
  61         store_32(&q->nodes[node].value, val);
  62         tmp = atomic_load(&q->nodes[node].next);
  63         set_ptr(&tmp, 0); // NULL
  64         atomic_store(&q->nodes[node].next, tmp);
  65
  66         while (!success) {
  67                 tail = atomic_load(&q->tail);
  68                 next = atomic_load(&q->nodes[get_ptr(tail)].next);
  69                 if (tail == atomic_load(&q->tail)) {
  70                         if (get_ptr(next) == 0) { // == NULL
  71                                 pointer value = MAKE_POINTER(node, get_count(next) + 1);
  72                                 success = atomic_compare_exchange_weak(&q->nodes[get_ptr(tail)].next,
  73                                                 &next, value);
  74                         }
  75                         if (!success) {
  76                                 unsigned int ptr = get_ptr(atomic_load(&q->nodes[get_ptr(tail)].next));
  77                                 pointer value = MAKE_POINTER(ptr,
  78                                                 get_count(tail) + 1);
  79                                 atomic_compare_exchange_strong(&q->tail,
  80                                                 &tail, value);
  81                                 thrd_yield();
  82                         }
  83                 }
  84         }
  85         atomic_compare_exchange_strong(&q->tail,
  86                         &tail,
  87                         MAKE_POINTER(node, get_count(tail) + 1));
  88 }
  89
  90 unsigned int dequeue(queue_t *q)
  91 {
  92         unsigned int value;
  93         int success = 0;
  94         pointer head;
  95         pointer tail;
  96         pointer next;
  97
  98         while (!success) {
  99                 head = atomic_load(&q->head);
 100                 tail = atomic_load(&q->tail);
 101                 next = atomic_load(&q->nodes[get_ptr(head)].next);
 102                 if (atomic_load(&q->head) == head) {
 103                         if (get_ptr(head) == get_ptr(tail)) {
 104                                 if (get_ptr(next) == 0) { // NULL
 105                                         return 0; // NULL
 106                                 }
 107                                 atomic_compare_exchange_strong(&q->tail,
 108                                                 &tail,
 109                                                 MAKE_POINTER(get_ptr(next), get_count(tail) + 1));
 110                                 thrd_yield();
 111                         } else {
 112                                 value = load_32(&q->nodes[get_ptr(next)].value);
 113                                 success = atomic_compare_exchange_weak(&q->head,
 114                                                 &head,
 115                                                 MAKE_POINTER(get_ptr(next), get_count(head) + 1));
 116                                 if (!success)
 117                                         thrd_yield();
 118                         }
 119                 }
 120         }
 121         reclaim(get_ptr(head));
 122         return value;
 123 }