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;
  12 atomic_int y;
  13 atomic_intptr_t z;
  14 atomic_intptr_t z2;
  15
  16 int r1, r2, r3; /* "local" variables */
  17
  18 /**
  19                 This example illustrates a self-satisfying cycle involving
  20                 synchronization.  A failed synchronization creates the store that
  21                 causes the synchronization to fail.
  22
  23                 The C++11 memory model nominally allows r1=0, r2=1, r3=5.
  24
  25                 This example is insane, we don't support that behavior.
  26 */
  27
  28
  29 static void a(void *obj)
  30 {
  31         z.store((intptr_t)&y, memory_order_relaxed);
  32         r1 = y.fetch_add(1, memory_order_release);
  33         z.store((intptr_t)&x, memory_order_relaxed);
  34         r2 = y.fetch_add(1, memory_order_release);
  35 }
  36
  37
  38 static void b(void *obj)
  39 {
  40         r3 = y.fetch_add(1, memory_order_acquire);
  41         void *ptr = (void *)z.load(memory_order_relaxed);
  42         z2.store((intptr_t)ptr, memory_order_relaxed);
  43 }
  44
  45 static void c(void *obj)
  46 {
  47         atomic_int *ptr2 = (atomic_int *)z2.load(memory_order_relaxed);
  48         (*ptr2).store(5, memory_order_relaxed);
  49 }
  50
  51 int user_main(int argc, char **argv)
  52 {
  53         thrd_t t1, t2, t3;
  54
  55         atomic_init(&x, 0);
  56         atomic_init(&y, 0);
  57         atomic_init(&z, (intptr_t) &x);
  58         atomic_init(&z2, (intptr_t) &x);
  59
  60         thrd_create(&t1, (thrd_start_t)&a, NULL);
  61         thrd_create(&t2, (thrd_start_t)&b, NULL);
  62         thrd_create(&t3, (thrd_start_t)&c, NULL);
  63
  64         thrd_join(t1);
  65         thrd_join(t2);
  66         thrd_join(t3);
  67
  68         printf("r1=%d, r2=%d, r3=%d\n", r1, r2, r3);
  69
  70         return 0;
  71 }