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

在 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

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。
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.te 和 vehicle_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

在 checkIfAlive 中，执行健康检查。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.h 和 WatchogClient.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

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。
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。

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.cpp 和 WatchogClient.cpp 的以下代码：

VehicleService.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;
}

供应商服务（原生）

指定汽车监控定时器 AIDL makefile

在 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

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.te 和 file_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

在 checkIfAlive 中，执行健康检查。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.h 和 SampleNativeClient.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。

使用名称搜索守护程序并调用 ICarWatchdog::registerClient。请参阅 main.cpp 和 SampleNativeClient.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

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

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

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。

汽车监控定时器

供应商 HAL

在 makefile 中指定汽车监控定时器 AIDL

添加 SELinux 政策

system_server.te

hal_vehicle_default.te

通过继承 BnCarWatchdogClient 实现客户端类

WatchogClient.h

WatchogClient.cpp

启动 binder 线程并注册客户端

VehicleService.cpp

WatchogClient.cpp

供应商服务（原生）

指定汽车监控定时器 AIDL makefile

添加 SELinux 政策

sample_client.te

file_contexts

通过继承 BnCarWatchdogClient 实现客户端类

SampleNativeClient.h

SampleNativeClient.cpp

启动 binder 线程并注册客户端

main.cpp

SampleNativeClient.cpp

供应商服务 (Android)

通过继承 CarWatchdogClientCallback 实现客户端

注册客户端

取消注册客户端

检测被汽车监控定时器终止的进程