libcruft-util/test/thread/spinlock.cpp

/*
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/.
 *
 * Copyright 2018 Danny Robson <danny@nerdcruft.net>
 */

#include "thread/flag.hpp"
#include "thread/spinlock.hpp"

#include "tap.hpp"

#include <mutex>
#include <thread>


///////////////////////////////////////////////////////////////////////////////
void
fight (cruft::thread::flag &start, cruft::thread::spinlock &l, int iterations)
{
    start.wait ();
    for (int count = 0; count < iterations; ++count)
        std::lock_guard g (l);
};


//-----------------------------------------------------------------------------
int
main ()
{
    cruft::TAP::logger tap;

    cruft::thread::spinlock l;
    l.lock ();
    tap.expect (true, "locked without contention");

    l.unlock ();
    tap.expect (true, "unlocked without contention");

    if (std::thread::hardware_concurrency () < 2) {
        tap.skip ("n-way fight");
    } else {
        constexpr int iterations = 1 << 12;
        cruft::thread::flag start_flag;

        std::vector<std::thread> contestants;
        for (unsigned i = 0; i < std::thread::hardware_concurrency (); ++i)
            contestants.emplace_back (fight, std::ref (start_flag), std::ref (l), iterations);

        start_flag.notify_all ();

        for (auto &t: contestants)
            t.join ();

        tap.expect (true, "n-way fight, {} contestants", std::thread::hardware_concurrency ());
    }

    return tap.status ();
}