tests/test-progs/pthread/src/test_std_mutex.cpp

/*
  * Copyright (c) 2018, Cornell University
  * All rights reserved.
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  * notice, this list of conditions and the following disclaimer.
  *
  * Redistributions in binary form must reproduce the above
  * copyright notice, this list of conditions and the following
  * disclaimer in the documentation and/or other materials provided
  * with the distribution.
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  * Neither the name of Cornell University nor the names of its
  * contributors may be used to endorse or promote products derived
  * from this software without specific prior written permission.
  *
  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
  * CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES,
  * INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
  * MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  * DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
  * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
  * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
  * USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  * ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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  *
  * Authors: Tuan Ta, Moyang Wang
  */

#include <cstdlib>
#include <iostream>
#include <mutex>
#include <thread>
#include <vector>

//------------------------------------------------------------------------
// Create n threads, run them in parallel and wait for them in the master
// thread.
// Each child thread increments a shared variable m times
//------------------------------------------------------------------------

#define MAX_N_WORKER_THREADS 10

int main( int argc, const char* argv[] )
{
    int n_worker_threads = 0;

    // allocate all threads
    std::vector< std::thread > threads;

    // mutex to protect the shared variable
    std::mutex my_mutex;

    // variable shared among all threads
    int shared_var = 0;

    // number of steps each thread increments the shared_var
    int nsteps = 1000;

    for ( int tid = 0; tid < MAX_N_WORKER_THREADS; ++tid ) {
        try {
            threads.push_back( std::thread( [&] {
                        std::lock_guard<std::mutex> guard(my_mutex);
                        for ( int i = 0; i < nsteps; ++i )
                            shared_var++;
                    } ) );
        } catch ( const std::system_error& err ) {
            break;
        }
        n_worker_threads++;
    }

    // sync up all threads
    for (int i = 0; i < n_worker_threads; ++i) {
        threads[i].join();
    }

    // verify
    if ( shared_var != n_worker_threads * nsteps || n_worker_threads < 1) {
        return EXIT_FAILURE;
    }

    return EXIT_SUCCESS;
}