benchmarks/cdschecker/dekker/dekker-fences.cc.in

   1 /*
   2  * Dekker's critical section algorithm, implemented with fences.
   3  *
   4  * URL:
   5  *   http://www.justsoftwaresolutions.co.uk/threading/
   6  */
   7
   8 #include <atomic>
   9 #include <threads.h>
  10
  11 #include "librace.h"
  12
  13 std::atomic<bool> flag0, flag1;
  14 std::atomic<int> turn;
  15 std::atomic<int> var;
  16
  17 void p0() {
  18         flag0.store(true);
  19
  20         while (flag1.load()) {
  21                 if (turn.load() !=0)
  22                 {
  23                         flag0.store(false);
  24                         while (turn.load() != 0) {
  25                                 thrd_yield();
  26                         }
  27                         flag0.store(true);
  28                 } else
  29                         thrd_yield();
  30         }
  31
  32         // critical section
  33         var.store(1);
  34
  35         turn.store(1);
  36         flag0.store(false);
  37 }
  38
  39 void p1() {
  40         flag1.store(true);
  41
  42         while (flag0.load()) {
  43                 if (turn.load() != 1) {
  44                         flag1.store(false);
  45                         while (turn.load() != 1) {
  46                                 thrd_yield();
  47                         }
  48                         flag1.store(true);
  49                 } else
  50                         thrd_yield();
  51         }
  52
  53         // critical section
  54         var.store(2);
  55
  56         turn.store(0);
  57         flag1.store(false);
  58 }
  59
  60 void p0l(void *arg) {
  61         int i;
  62         for(i=0;i<PROBLEMSIZE;i++)
  63                 p0();
  64 }
  65
  66 void p1l(void *arg) {
  67         int i;
  68         for(i=0;i<PROBLEMSIZE;i++)
  69                 p1();
  70 }
  71
  72 int user_main(int argc, char **argv)
  73 {
  74         thrd_t a, b;
  75
  76         flag0 = false;
  77         flag1 = false;
  78         turn = 0;
  79         var=0;
  80
  81         thrd_create(&a, p0l, NULL);
  82         thrd_create(&b, p1l, NULL);
  83
  84         thrd_join(a);
  85         thrd_join(b);
  86
  87         return 0;
  88 }