#include <pthread.h>
#include <stdlib.h>
#include <stdio.h>
#include <stdint.h>

#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>

pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;

int v[4];

unsigned long counts[4];
unsigned long count;

void* thread(void* X) {
  const int mine=(uintptr_t)X;
  for (;;) {
    pthread_mutex_lock(&lock);
    v[mine]=1;
    if (v[0]+v[1]+v[2]+v[3]!=1) {
      write(1,"KAPUTT!\n",8);
      exit(1);
    }
    v[mine]=0;
    ++counts[mine];
    if (++count%1000000==0) {
      char buf[100];
      sprintf(buf,"%d  \r",count);
      write(1,buf,strlen(buf));
    }
    pthread_mutex_unlock(&lock);
  }
}

int main() {
  pthread_t p[4];
  pthread_mutex_lock(&lock);
  pthread_mutex_unlock(&lock);
  puts("This test runs for 5 seconds (or it fails early).");
  pthread_create(&p[0],0,thread,(void*)0);
  pthread_create(&p[1],0,thread,(void*)1);
  pthread_create(&p[2],0,thread,(void*)2);
  pthread_create(&p[3],0,thread,(void*)3);
  sleep(5);
  printf("%lu iterations: %lu %lu %lu %lu.\n",count,counts[0],counts[1],counts[2],counts[3]);
  exit(0);
}