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); // sc
  32         size_t t = atomic_load_explicit(&q->top, memory_order_release);
  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,
  40                                 memory_order_acquire, memory_order_relaxed)) // sc
  41                                 /* Failed race. */
  42                                 x = EMPTY;
  43                         atomic_store_explicit(&q->bottom, b + 1, memory_order_relaxed);
  44                 }
  45         } else { /* Empty queue. */
  46                 x = EMPTY;
  47                 atomic_store_explicit(&q->bottom, b + 1, memory_order_relaxed);
  48         }
  49         return x;
  50 }
  51
  52 void resize(Deque *q) {
  53         Array *a = (Array *) atomic_load_explicit(&q->array, memory_order_relaxed);
  54         size_t size=atomic_load_explicit(&a->size, memory_order_relaxed);
  55         size_t new_size=size << 1;
  56         Array *new_a = (Array *) calloc(1, new_size * sizeof(atomic_int) + sizeof(Array));
  57         size_t top=atomic_load_explicit(&q->top, memory_order_relaxed);
  58         size_t bottom=atomic_load_explicit(&q->bottom, memory_order_relaxed);
  59         atomic_store_explicit(&new_a->size, new_size, memory_order_relaxed);
  60         size_t i;
  61         for(i=top; i < bottom; i++) {
  62                 atomic_store_explicit(&new_a->buffer[i % new_size], atomic_load_explicit(&a->buffer[i % size], memory_order_relaxed), memory_order_relaxed);
  63         }
  64         atomic_store_explicit(&q->array, new_a, memory_order_release); // release
  65         printf("resize\n");
  66 }
  67
  68 void push(Deque *q, int x) {
  69         size_t b = atomic_load_explicit(&q->bottom, memory_order_relaxed);
  70         size_t t = atomic_load_explicit(&q->top, memory_order_acquire); // acquire
  71         Array *a = (Array *) atomic_load_explicit(&q->array, memory_order_relaxed);
  72         if (b - t > atomic_load_explicit(&a->size, memory_order_relaxed) - 1) /* Full queue. */ {
  73                 resize(q);
  74                 //Bug in paper...should have next line...
  75                 a = (Array *) atomic_load_explicit(&q->array, memory_order_relaxed);
  76         }
  77         atomic_store_explicit(&a->buffer[b % atomic_load_explicit(&a->size, memory_order_relaxed)], x, memory_order_relaxed);
  78         atomic_thread_fence(memory_order_release); // release
  79         atomic_store_explicit(&q->bottom, b + 1, memory_order_relaxed);
  80 }
  81
  82 int steal(Deque *q) {
  83         size_t t = atomic_load_explicit(&q->top, memory_order_relaxed); // acquire
  84         atomic_thread_fence(memory_order_seq_cst); // sc
  85         size_t b = atomic_load_explicit(&q->bottom, memory_order_acquire); // acquire
  86         int x = EMPTY;
  87         if (t < b) {
  88                 /* Non-empty queue. */
  89                 Array *a = (Array *) atomic_load_explicit(&q->array, memory_order_acquire); // acquire
  90                 x = atomic_load_explicit(&a->buffer[t % atomic_load_explicit(&a->size, memory_order_relaxed)], memory_order_relaxed);
  91                 if (!atomic_compare_exchange_strong_explicit(&q->top, &t, t + 1,
  92                         memory_order_seq_cst, memory_order_relaxed)) // sc
  93                         /* Failed race. */
  94                         return ABORT;
  95         }
  96         return x;
  97 }