spinlock_false.cpp

spinlock_false.cpp

#include <cassert>
#include <iostream>
#include <atomic>
#include <thread>
#include <vector>
#include <string>

using namespace std;

atomic_bool l;
atomic_int i(0);

void check() {
    assert(i.load() == 0);
    i++;
    assert(i.load() == 1);
    i--;
    assert(i.load() == 0);
}

void hoge(int i) {
    for (int n = 0; n < 1000000; n++) {
      // Bug! Should be: `while (l.exchange(true));`
      while (l.load()); l.store(true);
      check();
      l.store(false);
    }
}

int main(int argc, char *argv[]) {
    if (argc != 2) return -1;
    string n(argv[1]);
    int N = stoi(n);

    l.store(false);

    vector<thread> v;
    for (int i = 0; i < N; i++) {
        v.push_back(thread(hoge, i));
    }

    for (int i = 0; i < N; i++) {
        v[i].join();
    }
    return 0;
}