product/deadlock/deadlock.cpp (9d5b420) - testcode.git

deadlock.cpp

#include <iostream>
#include <string>
#include <vector>
#include <thread>
#include <mutex>
#include <unistd.h>
#include <random>
#include <chrono>
#include "deadlock.hpp"

using namespace std;

namespace {

std::mutex left_chopstick;
std::mutex right_chopstick;

std::vector<std::thread> workers;

void do_work_on_right(bool, int32_t);

int get_rnd()
{
    static std::random_device rd;
    static std::mt19937 gen(rd());
    static std::uniform_int_distribution<> dis(100, 200);
    return dis(gen);
}

void do_work_on_left(bool have_right, int32_t tick)
{
    std::lock_guard<std::mutex> lm (left_chopstick);
    std::this_thread::sleep_for(std::chrono::milliseconds(get_rnd()));
    if (have_right) {
        std::cout << "deadlock::thread " << std::hex << this_thread::get_id() << " " << tick << endl;
    } else {
        do_work_on_right(true, tick);
    }
}

void do_work_on_right(bool have_left, int32_t tick)
{
    std::lock_guard<std::mutex> rm (right_chopstick);
    std::this_thread::sleep_for(std::chrono::milliseconds(get_rnd()));
    if (have_left) {
        std::cout << "deadlock::thread " << std::hex << this_thread::get_id() << " " << tick << endl;
    } else {
        do_work_on_left(true, tick);
    }
}

void work(int32_t ticks)
{
    for(int32_t tick = ticks; tick >= 0; tick--) {
        do_work_on_right(false, tick);
    }
}

};

int deadlock()
{
    uint32_t ticks = 10;
    cout << "The function " << __PRETTY_FUNCTION__ << " was called." << endl;
    cerr << "WARNING: Expect a deadlock. See http://wiki.dlma.com/gdb" << endl;

// Construct the thread right into the push_back() call.
    workers.push_back(std::thread([=]{
        for(uint32_t tick = 0; tick <= ticks; tick++) {
            do_work_on_left(false, tick);
            // usleep(get_rnd() * 1000);  // u for microseconds
        }
    }));

// Or, move the thread into the array.
    std::thread t2(work, ticks);
    workers.push_back(move(t2));

// Don't return before the other threads have finished.
    for (auto &w : workers) {
        if (w.joinable()) w.join();
    }
    return 0;
}

testcode.git

Added a routine to cause a deadlock. See http://wiki.dlma.com/gdb for more.