libcruft-util/test/job/spinlock.cpp

/*
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 *
 * Copyright 2018 Danny Robson <danny@nerdcruft.net>
 */

#include "job/flag.hpp"
#include "job/spinlock.hpp"
#include "tap.hpp"

#include <thread>
#include <mutex>


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


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

    util::job::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;
        util::job::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 ();

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

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