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汽车监控定时器

使用汽车监控定时器帮助调试 VHAL。汽车监控定时器可监控进程的运行状况并终止运行状况不佳的进程。如需通过汽车监控定时器监控某个进程,必须向汽车监控定时器注册该进程。当汽车监控定时器终止运行状况不佳的进程时,它会像其他“应用无响应”(ANR) 转储一样,将进程的状态写入 data/anr。这样做有助于执行调试过程。

本文将介绍供应商 HAL 和服务如何向汽车监控定时器注册进程。

供应商 HAL

通常,供应商 HAL 会使用 hwbinder 对应的线程池。但是,汽车监控定时器客户端会通过 binder(不同于 hwbinder)与汽车监控定时器守护程序通信。因此,供应商 HAL 会使用 binder 对应的线程池。

在 makefile 中指定汽车监控定时器 AIDL

  1. shared_libs 中添加 carwatchdog_aidl_interface-ndk_platform

    Android.bp

    cc_defaults {
        name: "vhal_v2_0_defaults",
        shared_libs: [
            "libbinder_ndk",
            "libhidlbase",
            "liblog",
            "libutils",
            "android.hardware.automotive.vehicle@2.0",
            "carwatchdog_aidl_interface-ndk_platform",
        ],
        cflags: [
            "-Wall",
            "-Wextra",
            "-Werror",
        ],
    }
    

添加 SELinux 政策

  1. 允许 system_server 终止您的 HAL。如果您没有 system_server.te,请创建一个。强烈建议您为每台设备添加一个 SELinux 政策。
  2. 允许供应商 HAL 使用 binder(binder_use 宏),并将供应商 HAL 添加到 carwatchdog 客户端域(carwatchdog_client_domain 宏)中。请参阅 systemserver.tevehicle_default.te 的以下代码:

    system_server.te

    # Allow system_server to kill vehicle HAL
    allow system_server hal_vehicle_server:process sigkill;
    

    hal_vehicle_default.te

    # Configuration for register VHAL to car watchdog
    carwatchdog_client_domain(hal_vehicle_default)
    binder_use(hal_vehicle_default)
    

通过继承 BnCarWatchdogClient 实现客户端类

  1. checkIfAlive 中,执行运行状况检查。例如,发布到线程循环处理程序。如果运行状况良好,则调用 ICarWatchdog::tellClientAlive。 请参阅 WatchogClient.hWatchogClient.cpp 的以下代码:

    WatchogClient.h

    class WatchdogClient : public aidl::android::automotive::watchdog::BnCarWatchdogClient {
      public:
        explicit WatchdogClient(const ::android::sp<::android::Looper>& handlerLooper, VehicleHalManager* vhalManager);
    
    ndk::ScopedAStatus checkIfAlive(int32_t sessionId, aidl::android::automotive::watchdog::TimeoutLength timeout) override; ndk::ScopedAStatus prepareProcessTermination() override; };

    WatchogClient.cpp

    ndk::ScopedAStatus WatchdogClient::checkIfAlive(int32_t sessionId, TimeoutLength /*timeout*/) {
        // Implement or call your health check logic here
        return ndk::ScopedAStatus::ok();
    }
    

启动 binder 线程并注册客户端

  1. 为 binder 通信创建线程池。如果供应商 HAL 将 hwbinder 用于自己的目的,则您必须为汽车监控定时器 binder 通信再创建一个线程池。
  2. 使用名称搜索守护程序并调用 ICarWatchdog::registerClient。汽车监控定时器守护程序的接口名称为 android.automotive.watchdog.ICarWatchdog/default
  3. 根据服务响应能力,选择汽车监控定时器支持的以下三种超时之一,然后在对 ICarWatchdog::registerClient 的调用中传递该超时:
    • critical(3s)
    • moderate(5s)
    • normal(10s)
    请参阅 VehicleService.cppWatchogClient.cpp 的以下代码:

    VehicleService.cp

    int main(int /* argc */, char* /* argv */ []) {
        // Set up thread pool for hwbinder
        configureRpcThreadpool(4, false /* callerWillJoin */);
    
        ALOGI("Registering as service...");
        status_t status = service->registerAsService();
    
        if (status != OK) {
            ALOGE("Unable to register vehicle service (%d)", status);
            return 1;
        }
    
        // Setup a binder thread pool to be a car watchdog client.
        ABinderProcess_setThreadPoolMaxThreadCount(1);
        ABinderProcess_startThreadPool();
        sp<Looper> looper(Looper::prepare(0 /* opts */));
        std::shared_ptr<WatchdogClient> watchdogClient =
                ndk::SharedRefBase::make<WatchdogClient>(looper, service.get());
        // The current health check is done in the main thread, so it falls short of capturing the real
        // situation. Checking through HAL binder thread should be considered.
        if (!watchdogClient->initialize()) {
            ALOGE("Failed to initialize car watchdog client");
            return 1;
        }
        ALOGI("Ready");
        while (true) {
            looper->pollAll(-1 /* timeoutMillis */);
        }
    
        return 1;
    }
    

    WatchogClient.cpp

    bool WatchdogClient::initialize() {
        ndk::SpAIBinder binder(AServiceManager_getService("android.automotive.watchdog.ICarWatchdog/default"));
        if (binder.get() == nullptr) {
            ALOGE("Failed to get carwatchdog daemon");
            return false;
        }
        std::shared_ptr<ICarWatchdog> server = ICarWatchdog::fromBinder(binder);
        if (server == nullptr) {
            ALOGE("Failed to connect to carwatchdog daemon");
            return false;
        }
        mWatchdogServer = server;
    
        binder = this->asBinder();
        if (binder.get() == nullptr) {
            ALOGE("Failed to get car watchdog client binder object");
            return false;
        }
        std::shared_ptr<ICarWatchdogClient> client = ICarWatchdogClient::fromBinder(binder);
        if (client == nullptr) {
            ALOGE("Failed to get ICarWatchdogClient from binder");
            return false;
        }
        mTestClient = client;
        mWatchdogServer->registerClient(client, TimeoutLength::TIMEOUT_NORMAL);
        ALOGI("Successfully registered the client to car watchdog server");
        return true;
    }
    

供应商服务(原生)

指定汽车监控定时器 AIDL makefile

  1. shared_libs 中添加 carwatchdog_aidl_interface-ndk_platform

    Android.bp

    cc_binary {
        name: "sample_native_client",
        srcs: [
            "src/*.cpp"
        ],
        shared_libs: [
            "carwatchdog_aidl_interface-ndk_platform",
            "libbinder_ndk",
        ],
        vendor: true,
    }
    

添加 SELinux 政策

  1. 如需添加 SELinux 政策,请允许供应商服务域使用 binder(binder_use 宏),并将供应商服务域添加到 carwatchdog 客户端域(carwatchdog_client_domain 宏)中。请参阅 sample_client.tefile_contexts 的以下代码:

    sample_client.te

    type sample_client, domain;
    type sample_client_exec, exec_type, file_type, vendor_file_type;
    
    carwatchdog_client_domain(sample_client)
    
    init_daemon_domain(sample_client)
    binder_use(sample_client)
    

    file_contexts

    /vendor/bin/sample_native_client  u:object_r:sample_client_exec:s0
    

通过继承 BnCarWatchdogClient 实现客户端类

  1. checkIfAlive 中,执行运行状况检查。一种选择是发布到线程循环处理程序。如果运行状况良好,则调用 ICarWatchdog::tellClientAlive。 请参阅 SampleNativeClient.hSampleNativeClient.cpp 的以下代码:

    SampleNativeClient.h

    class SampleNativeClient : public BnCarWatchdogClient {
    public:
        ndk::ScopedAStatus checkIfAlive(int32_t sessionId, TimeoutLength
            timeout) override;
        ndk::ScopedAStatus prepareProcessTermination() override;
        void initialize();
    
    private:
        void respondToDaemon();
    private:
        ::android::sp<::android::Looper> mHandlerLooper;
        std::shared_ptr<ICarWatchdog> mWatchdogServer;
        std::shared_ptr<ICarWatchdogClient> mClient;
        int32_t mSessionId;
    };
    

    SampleNativeClient.cpp

    ndk::ScopedAStatus WatchdogClient::checkIfAlive(int32_t sessionId, TimeoutLength timeout) {
        mHandlerLooper->removeMessages(mMessageHandler,
            WHAT_CHECK_ALIVE);
        mSessionId = sessionId;
        mHandlerLooper->sendMessage(mMessageHandler,
            Message(WHAT_CHECK_ALIVE));
        return ndk::ScopedAStatus::ok();
    }
    // WHAT_CHECK_ALIVE triggers respondToDaemon from thread handler
    void WatchdogClient::respondToDaemon() {
      // your health checking method here
      ndk::ScopedAStatus status = mWatchdogServer->tellClientAlive(mClient,
            mSessionId);
    }
    

启动 binder 线程并注册客户端

汽车监控定时器守护程序的接口名称为 android.automotive.watchdog.ICarWatchdog/default

  1. 使用名称搜索守护程序并调用 ICarWatchdog::registerClient。请参阅 main.cppSampleNativeClient.cpp 的以下代码:

    main.cpp

    int main(int argc, char** argv) {
        sp<Looper> looper(Looper::prepare(/*opts=*/0));
    
        ABinderProcess_setThreadPoolMaxThreadCount(1);
        ABinderProcess_startThreadPool();
        std::shared_ptr<SampleNativeClient> client =
            ndk::SharedRefBase::make<SampleNatvieClient>(looper);
    
        // The client is registered in initialize()
        client->initialize();
        ...
    }
    

    SampleNativeClient.cpp

    void SampleNativeClient::initialize() {
        ndk::SpAIBinder binder(AServiceManager_getService(
            "android.automotive.watchdog.ICarWatchdog/default"));
        std::shared_ptr<ICarWatchdog> server =
            ICarWatchdog::fromBinder(binder);
        mWatchdogServer = server;
        ndk::SpAIBinder binder = this->asBinder();
        std::shared_ptr<ICarWatchdogClient> client =
            ICarWatchdogClient::fromBinder(binder)
        mClient = client;
        server->registerClient(client, TimeoutLength::TIMEOUT_NORMAL);
    }
    

供应商服务 (Android)

通过继承 CarWatchdogClientCallback 实现客户端

  1. 按下面所示修改新文件:
    private final CarWatchdogClientCallback mClientCallback = new CarWatchdogClientCallback() {
        @Override
        public boolean onCheckHealthStatus(int sessionId, int timeout) {
            // Your health check logic here
            // Returning true implies the client is healthy
            // If false is returned, the client should call
            // CarWatchdogManager.tellClientAlive after health check is
            // completed
        }
    
        @Override
        public void onPrepareProcessTermination() {}
    };
    

注册客户端

  1. 调用 CarWatchdogManager.registerClient()
    private void startClient() {
        CarWatchdogManager manager =
            (CarWatchdogManager) car.getCarManager(
            Car.CAR_WATCHDOG_SERVICE);
        // Choose a proper executor according to your health check method
        ExecutorService executor = Executors.newFixedThreadPool(1);
        manager.registerClient(executor, mClientCallback,
            CarWatchdogManager.TIMEOUT_NORMAL);
    }
    

取消注册客户端

  1. 服务完成时调用 CarWatchdogManager.unregisterClient()
    private void finishClient() {
        CarWatchdogManager manager =
            (CarWatchdogManager) car.getCarManager(
            Car.CAR_WATCHDOG_SERVICE);
        manager.unregisterClient(mClientCallback);
    }
    

检测被汽车监控定时器终止的进程

汽车监控定时器会在已向其注册的进程(供应商 HAL、供应商原生服务、供应商 Android 服务)卡死且无响应时,转储/终止这些进程。可通过检查 logcat 来检测此类转储。转储或终止有问题的进程后,汽车监控定时器会输出日志 carwatchdog killed process_name (pid:process_id)。因此:

$ adb logcat -s CarServiceHelper | fgrep "carwatchdog killed"

系统会捕获相关日志。例如,如果 KitchenSink 应用(汽车监控定时器客户端)卡死,系统会向日志中写入如下所示的代码行:

05-01 09:50:19.683   578  5777 W CarServiceHelper: carwatchdog killed com.google.android.car.kitchensink (pid: 5574)

如需确定 KitchenSink 应用卡死的原因或位置,请使用存储在 /data/anr 中的进程转储,就像使用 Activity ANR 案例一样。

$ adb root
$ adb shell grep -Hn "pid process_pid" /data/anr/*

以下示例输出特定于 KitchenSink 应用:

$ adb shell su root grep -Hn "pid 5574" /data/anr/*.
/data/anr/anr_2020-05-01-09-50-18-290:3:----- pid 5574 at 2020-05-01 09:50:18 -----
/data/anr/anr_2020-05-01-09-50-18-290:285:----- Waiting Channels: pid 5574 at 2020-05-01 09:50:18 -----

找到转储文件(例如,以上示例中的 /data/anr/anr_2020-05-01-09-50-18-290),并开始进行分析。