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Other服务

追踪 startOtherServices 的设备条件、并行预加载、WMS/Input/Network/UI 服务依赖和失败传播。

基于android-17.0.0_r1
AndroidSystemServerSystemService源码阅读
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Other服务 ​

startOtherServices() 是 SystemServer 中最容易被写成“服务列表”的方法，但 Android 17 的实现更像一个条件驱动的编排器：它读取 feature/property，保存跨服务实例，启动 secondary Zygote preload，并在 PHASE_WAIT_FOR_SENSOR_SERVICE 后建立 WindowManager、InputManager、DisplayManager 的闭环。本文只解释代表性的依赖与状态，不复制数百个服务名。

1. 入口状态 ​

源码文件：frameworks/base/services/java/com/android/server/SystemServer.java

java
private void startOtherServices(@NonNull TimingsTraceAndSlog t) {
    t.traceBegin("startOtherServices");
    mSystemServiceManager.updateOtherServicesStartIndex();

    final Context context = mSystemContext;
    DynamicSystemService dynamicSystem = null;
    IStorageManager storageManager = null;
    WindowManagerService wm = null;
    InputManagerService inputManager = null;

    boolean disableNetworkTime = SystemProperties.getBoolean(
            "config.disable_networktime", false);
    boolean disableCameraService = SystemProperties.getBoolean(
            "config.disable_cameraservice", false);
    boolean isWatch = RoSystemFeatures.hasFeatureWatch(context);
    boolean isTv = RoSystemFeatures.hasFeatureLeanback(context);
    boolean isAutomotive = RoSystemFeatures.hasFeatureAutomotive(context);

updateOtherServicesStartIndex() 记录 Other 组在 SystemServiceManager 服务数组中的起点，方便后续 boot phase 和诊断区分。局部变量保存跨段传递的服务实例；feature/property 则决定某些服务是否进入启动图。isWatch/isTv/isAutomotive 不是展示信息，它们会直接改变 Vibrator、输入、网络和安全服务分支。

2. Secondary预加载 ​

源码文件：frameworks/base/services/java/com/android/server/SystemServer.java

java
final String SECONDARY_ZYGOTE_PRELOAD = "SecondaryZygotePreload";
mZygotePreload = SystemServerInitThreadPool.submit(() -> {
    try {
        TimingsTraceAndSlog traceLog =
                TimingsTraceAndSlog.newAsyncLog();
        traceLog.traceBegin(SECONDARY_ZYGOTE_PRELOAD);
        String[] abis32 = Build.SUPPORTED_32_BIT_ABIS;
        if (abis32.length > 0
                && !Process.ZYGOTE_PROCESS.preloadDefault(abis32[0])) {
            Slog.e(TAG,
                    "Unable to preload default resources for secondary");
        }
        traceLog.traceEnd();
    } catch (Exception ex) {
        Slog.e(TAG,
                "Exception preloading default resources", ex);
    }
}, SECONDARY_ZYGOTE_PRELOAD);

该任务提前约一秒启动 secondary Zygote 默认资源预加载，以便后面的 WebView 32 位 RELRO fork 不必等待资源初始化。Future mZygotePreload 是状态 owner；任务失败只记录日志，真正需要它的消费者会在后续阶段等待或继续走降级路径。异步 trace 使用 newAsyncLog()，不能和主线程 trace 当成同一时间线。

3. 条件服务 ​

java
ServiceManager.addService("sec_key_att_app_id_provider",
        new KeyAttestationApplicationIdProviderService(context));
mSystemServiceManager.startService(KeyChainSystemService.class);
mSystemServiceManager.startService(BinaryTransparencyService.class);
ServiceManager.addService("scheduling_policy",
        new SchedulingPolicyService());

if (com.android.server.ui_latency_stats.Flags
        .uiLatencyStatsService()) {
    mSystemServiceManager.startService(
            com.android.server.uilatencystats.UiLatencyStatsService.class);
}

Other 组同时使用 ServiceManager.addService() 和 SystemServiceManager.startService()：前者发布跨进程 Binder 名称，后者管理 SystemService 实例和生命周期。UI latency service 由 flag 控制，不能从未启动的 Binder 名称反推设备故障。

4. 内容服务 ​

java
if (mPackageManager.hasSystemFeature(
        PackageManager.FEATURE_MICROPHONE)
        || mPackageManager.hasSystemFeature(
        PackageManager.FEATURE_TELECOM)
        || mPackageManager.hasSystemFeature(
        PackageManager.FEATURE_TELEPHONY)) {
    mSystemServiceManager.startService(
            TelecomLoaderService.class);
}

TelephonyRegistry telephonyRegistry =
        new TelephonyRegistry(context,
                new TelephonyRegistry.ConfigurationProvider());
ServiceManager.addService(
        "telephony.registry", telephonyRegistry);

mSystemServiceManager.startService(
        AccountManagerService.Lifecycle.class);
mSystemServiceManager.startService(
        ContentService.Lifecycle.class);
mActivityManagerService.getContentProviderHelper()
        .installSystemProviders();

TelecomLoader 只有在设备具备麦克风、telecom 或 telephony feature 时启动；TelephonyRegistry 直接发布 Binder。AccountManager 必须先于 ContentService，系统 provider 安装又必须在 ContentService 之后进行，随后 SettingsProvider 就绪，SQLite compatibility WAL flags 才重新激活。这是一条“服务构造→provider 消费→全局配置恢复”的依赖链。

5. UI与存储前置 ​

java
if (mFactoryTestMode != FactoryTest.FACTORY_TEST_LOW_LEVEL) {
    mSystemServiceManager.startService(
            StorageManagerService.Lifecycle.class);
    storageManager = IStorageManager.Stub.asInterface(
            ServiceManager.getService("mount"));
    mSystemServiceManager.startService(
            StorageStatsService.Lifecycle.class);
}

mSystemServiceManager.startService(
        UiModeManagerService.class);
mSystemServiceManager.startService(
        LocaleManagerService.class);
mSystemServiceManager.startService(
        AppHibernationService.class);

低级工厂模式跳过 StorageManager；正常模式先启动 StorageManager，再获取其 Binder 代理供后续通知/媒体服务使用。UiMode、Locale、AppHibernation 等服务不都拥有独立 Binder 调用链，但都依赖已建立的 SystemContext 和 PackageManager 状态。

6. WMS与Input ​

源码文件：frameworks/base/services/java/com/android/server/SystemServer.java

java
mSystemServiceManager.startBootPhase(
        t, SystemService.PHASE_WAIT_FOR_SENSOR_SERVICE);

wm = WindowManagerService.main(
        context, inputManager, !mFirstBoot,
        new PhoneWindowManager(),
        mActivityManagerService.mActivityTaskManager);
ServiceManager.addService(
        Context.WINDOW_SERVICE, wm, false,
        DUMP_FLAG_PRIORITY_CRITICAL
                | DUMP_FLAG_PRIORITY_HIGH
                | DUMP_FLAG_PROTO);

mActivityManagerService.setWindowManager(wm);
wm.onInitReady();

inputManager.setWindowManagerCallbacks(
        wm.getInputManagerCallback());
inputManager.start();
mDisplayManagerService.windowManagerAndInputReady();

WMS 启动前先推进到 PHASE_WAIT_FOR_SENSOR_SERVICE，因为 WMS 需要 SensorService；WMS 创建后发布 Binder，再回填 AMS。InputManager 只有在拿到 WMS callback 后才启动，DisplayManager 又要等 WindowManager 和 Input 都 ready。这三个服务形成双向依赖闭环，不能按“类名顺序”拆开理解。

7. 网络与设备条件 ​

java
if (mFactoryTestMode == FactoryTest.FACTORY_TEST_LOW_LEVEL) {
    Slog.i(TAG, "No Bluetooth Service (factory test)");
} else if (!context.getPackageManager().hasSystemFeature(
        PackageManager.FEATURE_BLUETOOTH)) {
    Slog.i(TAG,
            "No Bluetooth Service (Bluetooth Hardware Not Present)");
} else {
    mSystemServiceManager.startServiceFromJar(
            BLUETOOTH_SERVICE_CLASS,
            BLUETOOTH_APEX_SERVICE_JAR_PATH);
}

Bluetooth 的启动同时受工厂测试模式和硬件 feature 控制；NetworkTime、Camera、SystemTextClassifier 等也由 property 控制。读取条件后再看服务 trace，才能区分“跳过”和“启动失败”。

8. 失败与恢复 ​

Other 主体用一个 try/catch 包围大量服务启动，异常会记录 Failure starting core service 并重新抛出，最终回到 SystemServer.run()。部分 UI/Storage/Locale 服务则单独 reportWtf()，允许 SystemServer 继续启动并把局部故障交给默认 WTF handler。两种策略不同：前者是编排主线失败，后者是可降级服务失败。

bash
# 输入 Other 入口，输出 feature/property、并行任务和主要服务阶段。
rg -n "startOtherServices|updateOtherServicesStartIndex|FEATURE_|disableNetworkTime|disableCameraService|SecondaryZygotePreload" \
  frameworks/base/services/java/com/android/server/SystemServer.java

# 输入 WMS/Input/Display 关键调用，输出阶段依赖和 ready 闭环。
rg -n "PHASE_WAIT_FOR_SENSOR_SERVICE|WindowManagerService\.main|setWindowManagerCallbacks|inputManager\.start|windowManagerAndInputReady" \
  frameworks/base/services/java/com/android/server/SystemServer.java

下一篇将展开 startApexServices() 和服务启动封口；不会重复本文的 Other 条件分支、WMS/Input 闭环和 secondary preload。