drd/tests/rwlock_race.c

   1 /** Cause a race inside code protected by a reader lock.
   2  */
   3
   4
   5 /* Needed for older glibc's (2.3 and older, at least) who don't
   6    otherwise "know" about pthread_rwlock_anything or about
   7    PTHREAD_MUTEX_RECURSIVE (amongst things). */
   8
   9 #define _GNU_SOURCE 1
  10
  11 #include <pthread.h>
  12 #include <stdio.h>
  13 #include <unistd.h>
  14
  15
  16
  17 static pthread_rwlock_t s_rwlock;
  18 static int s_racy;
  19
  20 static void sleep_ms(const int ms)
  21 {
  22   struct timespec delay = { ms / 1000, (ms % 1000) * 1000 * 1000 };
  23   nanosleep(&delay, 0);
  24 }
  25
  26 static void* thread_func(void* arg)
  27 {
  28   pthread_rwlock_rdlock(&s_rwlock);
  29   s_racy++;
  30   pthread_rwlock_unlock(&s_rwlock);
  31   sleep_ms(100);
  32   return 0;
  33 }
  34
  35 int main(int argc, char** argv)
  36 {
  37   pthread_t thread1;
  38   pthread_t thread2;
  39
  40 #if 0
  41
  42   VALGRIND_DO_CLIENT_REQUEST_STMT(VG_USERREQ__DRD_TRACE_ADDR,
  43                                   &s_racy, 0, 0, 0, 0);
  44 #endif
  45
  46   pthread_rwlock_init(&s_rwlock, 0);
  47   pthread_create(&thread1, 0, thread_func, 0);
  48   pthread_create(&thread2, 0, thread_func, 0);
  49   pthread_join(thread1, 0);
  50   pthread_join(thread2, 0);
  51   pthread_rwlock_destroy(&s_rwlock);
  52
  53   fprintf(stderr, "Result: %d\n", s_racy);
  54
  55   return 0;
  56 }