C++中监视线程卡死并自动崩溃退出 WatchDog

发表于 分类于 Valine： 本文字数： 2.2k 阅读时长 ≈ 2 分钟

之前写过在Python中监视卡死崩溃退出并打印卡死处的调用堆栈

在此记录一下C++的版本，不过没有在代码层面实现堆栈打印，可以通过core dump和gdb来查看崩溃时的堆栈

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// WatchDog.h
#pragma once

#include <cstdint>
#include <mutex>
#include <thread>
#include <atomic>
#include <condition_variable>

class WatchDog {
public:
    WatchDog(int timeout=10, bool echo=false); // seconds
    ~WatchDog() { stop(); }
    void stop();
    void kick();

private:
    void dog();
    void bark();

private:
    const int _timeout;
    const int _echo;
    std::atomic<int64_t> _last_kicked_ts;

    std::mutex _mutex;
    bool _stopped; // protected by _mutex
    std::condition_variable _cond; // protected by _mutex

    std::thread _dog;
};

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// WatchDog.cpp
#include "WatchDog.h"
#include <iostream>

using namespace std;

namespace {

int64_t get_gmtime_us(){
    std::chrono::system_clock clock;
    return std::chrono::duration_cast<std::chrono::microseconds>(
        clock.now().time_since_epoch()).count();
}

} // namespace


WatchDog::WatchDog(int timeout, bool echo)
: _timeout(timeout)
, _echo(echo)
, _last_kicked_ts(get_gmtime_us())
, _stopped(false)
, _dog(&WatchDog::dog, this) {
}


void WatchDog::stop() {
    do {
        std::unique_lock<std::mutex> lock(_mutex);
        _stopped = true;
        _cond.notify_one(); // wake up the dog
    } while(false);
    
    try {
        _dog.join();
    }
    catch (...) {
        // it's ok, could already be dead
    }
}

void WatchDog::kick() {
    _last_kicked_ts = get_gmtime_us();
}

void WatchDog::dog() {
    std::unique_lock<std::mutex> lock(_mutex);
    while (true) {
        if (_stopped) return;

        int64_t ts = get_gmtime_us();
        if (ts - _last_kicked_ts > _timeout * 1000000) {
            bark();
        }

        if (_echo) {
            std::cout << "Successful dog check"
                << " [ts] " << ts
                << " [last_kicked_ts] " << _last_kicked_ts << std::endl;
        }

        // wake up when notified, or every N seconds
        int n = std::max(_timeout / 3, 1);
        _cond.wait_for(lock, std::chrono::seconds(n));
    }
}

void WatchDog::bark() {
    if (_echo) {
        std::cout << "\n!!!!! WATCH DOG FAILURE TRIGGERED !!!!!" << std::endl;
    }
    abort();
}