clang/test/seqlock_raw_unannotated.c

   1 #include <stdio.h>
   2 #include <threads.h>
   3 #include <stdatomic.h>
   4
   5 #include <stdatomic.h>
   6 #include "threads.h"
   7 #include "libinterface.h"
   8
   9 /*atomic_*/ int _seq;
  10 /*atomic_*/ int _data;
  11
  12 void seqlock_init() {
  13         store_32(&_seq, 0);
  14         store_32(&_data, 0);
  15 }
  16
  17 int seqlock_read() {
  18         while (true) {
  19                 int old_seq = load_32(&_seq);
  20
  21                 if (old_seq % 2 == 1) {
  22                 } else {
  23                         int res = load_32(&_data);
  24                         int seq = load_32(&_seq);
  25
  26                         if (seq == old_seq) { // relaxed
  27                                 return res;
  28                         }
  29                 }
  30         }
  31 }
  32
  33 void seqlock_write(int new_data) {
  34         while (true) {
  35                 int old_seq = load_32(&_seq);
  36                 if (old_seq % 2 == 1) {
  37                 } else {
  38                         int new_seq = old_seq + 1;
  39                         int cas_value = rmw_32(CAS, &_seq, old_seq, new_seq);
  40                         if (old_seq == cas_value) {
  41                                 break;
  42                         }
  43                 }
  44         }
  45         store_32(&_data, new_data);
  46
  47         rmw_32(ADD, &_seq, /*dummy */0, 1);
  48 }
  49
  50 static void a(void *obj) {
  51         seqlock_write(3);
  52 }
  53
  54 static void b(void *obj) {
  55         seqlock_write(2);
  56 }
  57
  58 static void c(void *obj) {
  59         int r1 = seqlock_read();
  60 }
  61
  62 int user_main(int argc, char **argv) {
  63         thrd_t t1, t2, t3;
  64         seqlock_init();
  65
  66         thrd_create(&t1, (thrd_start_t)&a, NULL);
  67         thrd_create(&t2, (thrd_start_t)&b, NULL);
  68         thrd_create(&t3, (thrd_start_t)&c, NULL);
  69
  70         thrd_join(t1);
  71         thrd_join(t2);
  72         thrd_join(t3);
  73         return 0;
  74 }