treiber-stack/stack_wildcard.c

   1 #include <threads.h>
   2 #include <stdlib.h>
   3 #include "librace.h"
   4 #include "model-assert.h"
   5
   6 #include "stack.h"
   7 #include "wildcard.h"
   8
   9 #define MAX_FREELIST 4 /* Each thread can own up to MAX_FREELIST free nodes */
  10 #define INITIAL_FREE 2 /* Each thread starts with INITIAL_FREE free nodes */
  11
  12 #define POISON_IDX 0x666
  13
  14 static unsigned int (*free_lists)[MAX_FREELIST];
  15
  16 /* Search this thread's free list for a "new" node */
  17 static unsigned int new_node()
  18 {
  19         int i;
  20         int t = get_thread_num();
  21         for (i = 0; i < MAX_FREELIST; i++) {
  22                 //unsigned int node = load_32(&free_lists[t][i]);
  23                 unsigned int node = free_lists[t][i];
  24                 if (node) {
  25                         //store_32(&free_lists[t][i], 0);
  26                         free_lists[t][i] = 0;
  27                         return node;
  28                 }
  29         }
  30         /* free_list is empty? */
  31         MODEL_ASSERT(0);
  32         return 0;
  33 }
  34
  35 /* Place this node index back on this thread's free list */
  36 static void reclaim(unsigned int node)
  37 {
  38         int i;
  39         int t = get_thread_num();
  40
  41         /* Don't reclaim NULL node */
  42         //MODEL_ASSERT(node);
  43
  44         for (i = 0; i < MAX_FREELIST; i++) {
  45                 /* Should never race with our own thread here */
  46                 //unsigned int idx = load_32(&free_lists[t][i]);
  47                 unsigned int idx = 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                         free_lists[t][i] = node;
  53                         return;
  54                 }
  55         }
  56         /* free list is full? */
  57         MODEL_ASSERT(0);
  58 }
  59
  60 void init_stack(stack_t *s, int num_threads)
  61 {
  62         int i, j;
  63
  64         /* Initialize each thread's free list with INITIAL_FREE pointers */
  65         /* The actual nodes are initialized with poison indexes */
  66         free_lists = malloc(num_threads * sizeof(*free_lists));
  67         for (i = 0; i < num_threads; i++) {
  68                 for (j = 0; j < INITIAL_FREE; j++) {
  69                         free_lists[i][j] = 1 + i * MAX_FREELIST + j;
  70                         atomic_init(&s->nodes[free_lists[i][j]].next, MAKE_POINTER(POISON_IDX, 0));
  71                 }
  72         }
  73
  74         /* initialize stack */
  75         atomic_init(&s->top, MAKE_POINTER(0, 0));
  76 }
  77
  78 void push(stack_t *s, unsigned int val) {
  79         unsigned int nodeIdx = new_node();
  80         node_t *node = &s->nodes[nodeIdx];
  81         node->value = val;
  82         pointer oldTop, newTop;
  83         bool success;
  84         while (true) {
  85                 // acquire
  86                 oldTop = atomic_load_explicit(&s->top, wildcard(1));
  87                 newTop = MAKE_POINTER(nodeIdx, get_count(oldTop) + 1);
  88                 // relaxed
  89                 atomic_store_explicit(&node->next, oldTop, wildcard(2));
  90
  91                 // release & relaxed
  92                 success = atomic_compare_exchange_strong_explicit(&s->top, &oldTop,
  93                         newTop, wildcard(3), wildcard(4));
  94                 if (success)
  95                         break;
  96         }
  97 }
  98
  99 unsigned int pop(stack_t *s)
 100 {
 101         pointer oldTop, newTop, next;
 102         node_t *node;
 103         bool success;
 104         int val;
 105         while (true) {
 106                 // acquire
 107                 oldTop = atomic_load_explicit(&s->top, wildcard(5));
 108                 if (get_ptr(oldTop) == 0)
 109                         return 0;
 110                 node = &s->nodes[get_ptr(oldTop)];
 111                 // relaxed
 112                 next = atomic_load_explicit(&node->next, wildcard(6));
 113                 newTop = MAKE_POINTER(get_ptr(next), get_count(oldTop) + 1);
 114                 // release & relaxed
 115                 success = atomic_compare_exchange_strong_explicit(&s->top, &oldTop,
 116                         newTop, wildcard(7), wildcard(8));
 117                 if (success)
 118                         break;
 119         }
 120         val = node->value;
 121         /* Reclaim the used slot */
 122         reclaim(get_ptr(oldTop));
 123         return val;
 124 }