chase-lev-deque-bugfix/deque.c

   1 #include <stdatomic.h>
   2 #include <inttypes.h>
   3 #include "deque.h"
   4 #include <stdlib.h>
   5 #include <stdio.h>
   6
   7 Deque * create_size(int size) {
   8         Deque * q = (Deque *) calloc(1, sizeof(Deque));
   9         Array * a = (Array *) calloc(1, sizeof(Array)+2*sizeof(atomic_int));
  10         atomic_store_explicit(&q->array, a, memory_order_relaxed);
  11         atomic_store_explicit(&q->top, 0, memory_order_relaxed);
  12         atomic_store_explicit(&q->bottom, 0, memory_order_relaxed);
  13         atomic_store_explicit(&a->size, size, memory_order_relaxed);
  14         return q;
  15 }
  16
  17 Deque * create() {
  18         Deque * q = (Deque *) calloc(1, sizeof(Deque));
  19         Array * a = (Array *) calloc(1, sizeof(Array)+2*sizeof(atomic_int));
  20         atomic_store_explicit(&q->array, a, memory_order_relaxed);
  21         atomic_store_explicit(&q->top, 0, memory_order_relaxed);
  22         atomic_store_explicit(&q->bottom, 0, memory_order_relaxed);
  23         atomic_store_explicit(&a->size, 2, memory_order_relaxed);
  24         return q;
  25 }
  26
  27 int take(Deque *q) {
  28         size_t b = atomic_load_explicit(&q->bottom, memory_order_relaxed) - 1;
  29         Array *a = (Array *) atomic_load_explicit(&q->array, memory_order_relaxed);
  30         atomic_store_explicit(&q->bottom, b, memory_order_relaxed);
  31         atomic_thread_fence(memory_order_seq_cst);
  32         size_t t = atomic_load_explicit(&q->top, memory_order_acquire); // relaxed
  33         int x;
  34         if (t <= b) {
  35                 /* Non-empty queue. */
  36                 x = atomic_load_explicit(&a->buffer[b % atomic_load_explicit(&a->size,memory_order_relaxed)], memory_order_relaxed);
  37                 if (t == b) {
  38                         /* Single last element in queue. */
  39                         if (!atomic_compare_exchange_strong_explicit(&q->top, &t, t + 1, memory_order_relaxed, memory_order_relaxed)) // seq_cst
  40                                 /* Failed race. */
  41                                 x = EMPTY;
  42                         atomic_store_explicit(&q->bottom, b + 1, memory_order_release); // relaxed
  43                 }
  44         } else { /* Empty queue. */
  45                 x = EMPTY;
  46                 atomic_store_explicit(&q->bottom, b + 1, memory_order_release); // relaxed
  47         }
  48         return x;
  49 }
  50
  51 void resize(Deque *q) {
  52         Array *a = (Array *) atomic_load_explicit(&q->array, memory_order_relaxed);
  53         size_t size=atomic_load_explicit(&a->size, memory_order_relaxed);
  54         size_t new_size=size << 1;
  55         Array *new_a = (Array *) calloc(1, new_size * sizeof(atomic_int) + sizeof(Array));
  56         size_t top=atomic_load_explicit(&q->top, memory_order_relaxed);
  57         size_t bottom=atomic_load_explicit(&q->bottom, memory_order_relaxed);
  58         atomic_store_explicit(&new_a->size, new_size, memory_order_relaxed);
  59         size_t i;
  60         for(i=top; i < bottom; i++) {
  61                 atomic_store_explicit(&new_a->buffer[i % new_size], atomic_load_explicit(&a->buffer[i % size], memory_order_relaxed), memory_order_relaxed);
  62         }
  63         atomic_store_explicit(&q->array, new_a, memory_order_release);
  64         printf("resize\n");
  65 }
  66
  67 void push(Deque *q, int x) {
  68         size_t b = atomic_load_explicit(&q->bottom, memory_order_relaxed);
  69         size_t t = atomic_load_explicit(&q->top, memory_order_acquire);
  70         Array *a = (Array *) atomic_load_explicit(&q->array, memory_order_relaxed);
  71         if (b - t > atomic_load_explicit(&a->size, memory_order_relaxed) - 1) /* Full queue. */ {
  72                 resize(q);
  73                 //Bug in paper...should have next line...
  74                 a = (Array *) atomic_load_explicit(&q->array, memory_order_relaxed);
  75         }
  76         atomic_store_explicit(&a->buffer[b % atomic_load_explicit(&a->size, memory_order_relaxed)], x, memory_order_relaxed);
  77         atomic_thread_fence(memory_order_release);
  78         atomic_store_explicit(&q->bottom, b + 1, memory_order_relaxed);
  79 }
  80
  81 int steal(Deque *q) {
  82         size_t t = atomic_load_explicit(&q->top, memory_order_relaxed); // acquire
  83         atomic_thread_fence(memory_order_seq_cst);
  84         size_t b = atomic_load_explicit(&q->bottom, memory_order_acquire);
  85         int x = EMPTY;
  86         if (t < b) {
  87                 /* Non-empty queue. */
  88                 Array *a = (Array *) atomic_load_explicit(&q->array, memory_order_acquire);
  89                 x = atomic_load_explicit(&a->buffer[t % atomic_load_explicit(&a->size, memory_order_relaxed)], memory_order_relaxed);
  90                 if (!atomic_compare_exchange_strong_explicit(&q->top, &t, t + 1, memory_order_seq_cst, memory_order_relaxed))
  91                         /* Failed race. */
  92                         return ABORT;
  93         }
  94         return x;
  95 }