本頁面由 Cloud Translation API 翻譯而成。

汽車看門狗

使用汽車看門狗幫助調試 VHAL。汽車看門狗監控並殺死不健康的進程。對於要被汽車看門狗監視的進程，該進程必須向汽車看門狗註冊。當汽車看門狗殺死不健康的進程時，汽車看門狗會將進程的狀態寫入data/anr ，就像其他應用程序無響應 (ANR) 轉儲一樣。這樣做有助於調試過程。

本文介紹供應商 HAL 和服務如何向汽車看門狗註冊進程。

供應商 HAL

通常，供應商 HAL 為hwbinder使用線程池。但是，汽車看門狗客戶端通過binder與汽車看門狗守護進程通信，這與hwbinder不同。因此，正在使用另一個用於binder的線程池。

在makefile中指定汽車看門狗aidl

在shared_libs中包含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 策略

允許system_server殺死你的 HAL。如果您沒有system_server.te ，請創建一個。強烈建議您為每台設備添加 SELinux 策略。
允許供應商 HAL 使用 binder（ binder_use宏）並將供應商 HAL 添加到carwatchdog客戶端域（ carwatchdog_client_domain宏）。請參閱下面的systemserver.te和vehicle_default.te代碼：
系統服務器.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)
```

通過繼承 BnCarWatchdogClient 實現一個客戶端類

在checkIfAlive中，執行健康檢查。例如，發佈到線程循環處理程序。如果健康，請致電ICarWatchdog::tellClientAlive 。請參閱下面的WatchogClient.h和WatchogClient.cpp代碼：

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();
}

啟動binder線程並註冊客戶端

為 binder 通信創建線程池。如果供應商 HAL 出於自身目的使用 hwbinder，則必須創建另一個線程池用於 car watchdog binder 通信）。
使用名稱搜索守護進程並調用ICarWatchdog::registerClient 。汽車看門狗守護進程接口名稱為android.automotive.watchdog.ICarWatchdog/default 。

根據服務響應能力，選擇汽車看門狗支持的以下三種超時類型之一，然後將超時傳遞給ICarWatchdog::registerClient調用：

關鍵（3s）
中等（5s）
正常(10s)

有關VehicleService.cpp和WatchogClient.cpp的代碼，請參見以下代碼：

車輛服務.cpp

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;
}

供應商服務（本機）

指定汽車看門狗aidl makefile

在shared_libs中包含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 策略

要添加 SELinux 策略，請允許供應商服務域使用 binder（ binder_use宏）並將供應商服務域添加到carwatchdog客戶端域（ carwatchdog_client_domain宏）。有關sample_client.te和file_contexts的信息，請參見下面的代碼：
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)
```
文件上下文
```
/vendor/bin/sample_native_client  u:object_r:sample_client_exec:s0
```

通過繼承 BnCarWatchdogClient 實現一個客戶端類

在checkIfAlive中，執行健康檢查。一種選擇是發佈到線程循環處理程序。如果健康，請致電ICarWatchdog::tellClientAlive 。請參閱下面的SampleNativeClient.h和SampleNativeClient.cpp代碼：

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;
};

示例 NativeClient.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);
}

啟動一個活頁夾線程並註冊客戶端

汽車看門狗守護進程接口名稱為android.automotive.watchdog.ICarWatchdog/default 。

使用名稱搜索守護進程並調用ICarWatchdog::registerClient 。請參閱下面的main.cpp和SampleNativeClient.cpp代碼：

主文件

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();
    ...
}

示例 NativeClient.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);
}

供應商服務 (Android)

通過繼承 CarWatchdogClientCallback 實現客戶端

編輯新文件如下：

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() {}
};

註冊客戶端

調用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);
}

註銷客戶端

服務完成後調用CarWatchdogManager.unregisterClient() ：

private void finishClient() {
    CarWatchdogManager manager =
        (CarWatchdogManager) car.getCarManager(
        Car.CAR_WATCHDOG_SERVICE);
    manager.unregisterClient(mClientCallback);
}

檢測被汽車看門狗終止的進程

汽車看門狗轉儲/殺死進程（供應商 HAL、供應商本機服務、供應商 Android 服務），這些進程在卡住且無響應時註冊到汽車看門狗。通過檢查 logcats 來檢測這種轉儲。當有問題的進程被轉儲或終止時，汽車看門狗會輸出日誌carwatchdog killed process_name (pid:process_id) 。因此：

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

相關日誌被捕獲。例如，如果 KitchenSink 應用程序（汽車看門狗客戶端）卡住，則會將如下一行寫入日誌：

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

要確定 KitchenSink 應用程序卡住的原因或位置，請使用存儲在/data/anr的進程轉儲，就像使用 Activity ANR 案例一樣。

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

以下示例輸出特定於 KitchenSink 應用程序：

$ 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 -----

找到轉儲文件（例如，上例中的/data/anr/anr_2020-05-01-09-50-18-290 ）並開始分析。

汽車看門狗

供應商 HAL

在makefile中指定汽車看門狗aidl

添加 SELinux 策略

系統服務器.te

hal_vehicle_default.te

通過繼承 BnCarWatchdogClient 實現一個客戶端類

WatchogClient.h

WatchogClient.cpp

啟動binder線程並註冊客戶端

車輛服務.cpp

WatchogClient.cpp

供應商服務（本機）

指定汽車看門狗aidl makefile

添加 SELinux 策略

sample_client.te

文件上下文

通過繼承 BnCarWatchdogClient 實現一個客戶端類

SampleNativeClient.h

示例 NativeClient.cpp

啟動一個活頁夾線程並註冊客戶端

主文件

示例 NativeClient.cpp

供應商服務 (Android)

通過繼承 CarWatchdogClientCallback 實現客戶端

註冊客戶端

註銷客戶端

檢測被汽車看門狗終止的進程