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 #define relaxed memory_order_relaxed
   8 #define release memory_order_release
   9 #define acquire memory_order_acquire
  10
  11 static unsigned int *node_nums;
  12
  13 static unsigned int new_node()
  14 {
  15         return node_nums[get_thread_num()];
  16 }
  17
  18 static void reclaim(unsigned int node)
  19 {
  20         node_nums[get_thread_num()] = node;
  21 }
  22
  23 void init_queue(queue_t *q, int num_threads)
  24 {
  25         unsigned int i;
  26         pointer head;
  27         pointer tail;
  28         pointer next;
  29
  30         node_nums = malloc(num_threads * sizeof(*node_nums));
  31         for (i = 0; i < num_threads; i++)
  32                 node_nums[i] = 2 + i;
  33
  34         /* Note: needed to add this init manually */
  35         atomic_init(&q->nodes[0].next, 0);
  36
  37         /* initialize queue */
  38         head = MAKE_POINTER(1, 0);
  39         tail = MAKE_POINTER(1, 0);
  40         next = MAKE_POINTER(0, 0); // (NULL, 0)
  41
  42         atomic_init(&q->head, head);
  43         atomic_init(&q->tail, tail);
  44         atomic_init(&q->nodes[1].next, next);
  45
  46         /* initialize avail list */
  47         for (i = 2; i < MAX_NODES; i++) {
  48                 next = MAKE_POINTER(i + 1, 0);
  49                 atomic_init(&q->nodes[i].next, next);
  50         }
  51
  52         next = MAKE_POINTER(0, 0); // (NULL, 0)
  53         atomic_init(&q->nodes[MAX_NODES].next, next);
  54 }
  55
  56 void enqueue(queue_t *q, unsigned int val)
  57 {
  58         int success = 0;
  59         unsigned int node;
  60         pointer tail;
  61         pointer next;
  62         pointer tmp;
  63
  64         node = new_node();
  65         store_32(&q->nodes[node].value, val);
  66         tmp = atomic_load_explicit(&q->nodes[node].next, relaxed);
  67         set_ptr(&tmp, 0); // NULL
  68         atomic_store_explicit(&q->nodes[node].next, tmp, relaxed);
  69
  70         while (!success) {
  71                 tail = atomic_load_explicit(&q->tail, acquire);
  72                 next = atomic_load_explicit(&q->nodes[get_ptr(tail)].next, acquire);
  73                 if (tail == atomic_load_explicit(&q->tail, relaxed)) {
  74                         if (get_ptr(next) == 0) { // == NULL
  75                                 pointer value = MAKE_POINTER(node, get_count(next) + 1);
  76                                 success = atomic_compare_exchange_strong_explicit(&q->nodes[get_ptr(tail)].next,
  77                                                 &next, value, memory_order_acq_rel, memory_order_acq_rel);
  78                         }
  79                         if (!success) {
  80                                 unsigned int ptr = get_ptr(atomic_load_explicit(&q->nodes[get_ptr(tail)].next, memory_order_seq_cst));
  81                                 pointer value = MAKE_POINTER(ptr,
  82                                                 get_count(tail) + 1);
  83                                 atomic_compare_exchange_strong_explicit(&q->tail,
  84                                                 &tail, value,
  85                                                 memory_order_acq_rel, memory_order_acq_rel);
  86                                 thrd_yield();
  87                         }
  88                 }
  89         }
  90         atomic_compare_exchange_strong_explicit(&q->tail,
  91                         &tail,
  92                         MAKE_POINTER(node, get_count(tail) + 1),
  93                         memory_order_acq_rel, memory_order_acq_rel);
  94 }
  95
  96 unsigned int dequeue(queue_t *q)
  97 {
  98         unsigned int value;
  99         int success = 0;
 100         pointer head;
 101         pointer tail;
 102         pointer next;
 103
 104         while (!success) {
 105                 head = atomic_load_explicit(&q->head, acquire);
 106                 tail = atomic_load_explicit(&q->tail, acquire);
 107                 next = atomic_load_explicit(&q->nodes[get_ptr(head)].next, acquire);
 108                 if (atomic_load_explicit(&q->head, relaxed) == head) {
 109                         if (get_ptr(head) == get_ptr(tail)) {
 110                                 if (get_ptr(next) == 0) { // NULL
 111                                         return 0; // NULL
 112                                 }
 113                                 atomic_compare_exchange_strong_explicit(&q->tail,
 114                                                 &tail,
 115                                                 MAKE_POINTER(get_ptr(next), get_count(tail) + 1),
 116                                                 memory_order_acq_rel, memory_order_acq_rel);
 117                                 thrd_yield();
 118                         } else {
 119                                 value = load_32(&q->nodes[get_ptr(next)].value);
 120                                 success = atomic_compare_exchange_strong_explicit(&q->head,
 121                                                 &head,
 122                                                 MAKE_POINTER(get_ptr(next), get_count(head) + 1),
 123                                                 memory_order_acq_rel, memory_order_acq_rel);
 124                                 if (!success)
 125                                         thrd_yield();
 126                         }
 127                 }
 128         }
 129         reclaim(get_ptr(head));
 130         return value;
 131 }