test/insanesync.cc

   1 #include <stdlib.h>
   2 #include <stdio.h>
   3 #include <threads.h>
   4 #include <atomic>
   5
   6 #include "librace.h"
   7 #include "model-assert.h"
   8
   9 using namespace std;
  10
  11 atomic_int x, y;
  12 atomic_intptr_t z, z2;
  13
  14 int r1, r2, r3; /* "local" variables */
  15
  16 /**
  17                 This example illustrates a self-satisfying cycle involving
  18                 synchronization.  A failed synchronization creates the store that
  19                 causes the synchronization to fail.
  20
  21                 The C++11 memory model nominally allows r1=0, r2=1, r3=5.
  22
  23                 This example is insane, we don't support that behavior.
  24 */
  25
  26
  27 static void a(void *obj)
  28 {
  29         z.store((intptr_t)&y, memory_order_relaxed);
  30         r1 = y.fetch_add(1, memory_order_release);
  31         z.store((intptr_t)&x, memory_order_relaxed);
  32         r2 = y.fetch_add(1, memory_order_release);
  33 }
  34
  35
  36 static void b(void *obj)
  37 {
  38         r3 = y.fetch_add(1, memory_order_acquire);
  39         intptr_t ptr = z.load(memory_order_relaxed);
  40         z2.store(ptr, memory_order_relaxed);
  41 }
  42
  43 static void c(void *obj)
  44 {
  45         atomic_int *ptr2 = (atomic_int *)z2.load(memory_order_relaxed);
  46         (*ptr2).store(5, memory_order_relaxed);
  47 }
  48
  49 int user_main(int argc, char **argv)
  50 {
  51         thrd_t t1, t2, t3;
  52
  53         atomic_init(&x, 0);
  54         atomic_init(&y, 0);
  55         atomic_init(&z, (intptr_t) &x);
  56         atomic_init(&z2, (intptr_t) &x);
  57
  58         thrd_create(&t1, (thrd_start_t)&a, NULL);
  59         thrd_create(&t2, (thrd_start_t)&b, NULL);
  60         thrd_create(&t3, (thrd_start_t)&c, NULL);
  61
  62         thrd_join(t1);
  63         thrd_join(t2);
  64         thrd_join(t3);
  65
  66         printf("r1=%d, r2=%d, r3=%d\n", r1, r2, r3);
  67
  68         return 0;
  69 }