A simple example demonstrating the coredump problem

core_share.cpp

#include <iostream>
#include <thread>
#include <unordered_map>
#include <shared_mutex>
#include <vector>
#include <random>
class DataManager {
private:
    std::shared_mutex mutex_;
    std::unordered_map<std::string, std::string> m_data;
public:
    int num_keys = 100;
    void loadData() {
        std::unordered_map<std::string, std::string> localdata;
        std::vector<std::string> keys;
        for(int i = 0; i < num_keys; i++) {
            keys.push_back("test" + std::to_string(i));
        }

        for(int i = 0; i < num_keys; i++) {
            localdata[keys[i]] = "test" + std::to_string(i);
        }
        {
            std::unique_lock<std::shared_mutex> lock(mutex_);
            m_data.swap(localdata);
        }
    }

    std::string readData(const std::string& key) {

        {
            std::shared_lock<std::shared_mutex> lock(mutex_);
            return m_data[key];
        }
        return 0;
    }
};

void readerThread(DataManager& dm, int id) {
    while (true) {
        int key = rand() % dm.num_keys + dm.num_keys / 2;
        std::string key_str = "test" + std::to_string(key);
        std::string result = dm.readData(key_str);
    }
}

void loaderThread(DataManager& dm) {
    while (true) {
        dm.loadData();
    }
}

int main() {
    DataManager dm;
    std::thread loader(loaderThread, std::ref(dm));
    std::vector<std::thread> readers;
    for (int i = 0; i < 4; i++) {
        readers.emplace_back(readerThread, std::ref(dm), i);
    }

    loader.join();
    for (auto& t : readers) {
        t.join();
    }

    return 0;
}