SystemServer.java的run方法都干了些什么？(2)

private void run() {

TimingsTraceAndSlog t = new TimingsTraceAndSlog();

try {

t.traceBegin("InitBeforeStartServices");

// Record the process start information in sys props.

SystemProperties.set(SYSPROP_START_COUNT, String.valueOf(mStartCount));

SystemProperties.set(SYSPROP_START_ELAPSED, String.valueOf(mRuntimeStartElapsedTime));

SystemProperties.set(SYSPROP_START_UPTIME, String.valueOf(mRuntimeStartUptime));

EventLog.writeEvent(EventLogTags.SYSTEM_SERVER_START,

mStartCount, mRuntimeStartUptime, mRuntimeStartElapsedTime);

//

// Default the timezone property to GMT if not set.

//

String timezoneProperty = SystemProperties.get("persist.sys.timezone");

if (timezoneProperty == null || timezoneProperty.isEmpty()) {

Slog.w(TAG, "Timezone not set; setting to GMT.");

SystemProperties.set("persist.sys.timezone", "GMT");

}

// If the system has "persist.sys.language" and friends set, replace them with

// "persist.sys.locale". Note that the default locale at this point is calculated

// using the "-Duser.locale" command line flag. That flag is usually populated by

// AndroidRuntime using the same set of system properties, but only the system_server

// and system apps are allowed to set them.

//

// NOTE: Most changes made here will need an equivalent change to

// core/jni/AndroidRuntime.cpp

if (!SystemProperties.get("persist.sys.language").isEmpty()) {

final String languageTag = Locale.getDefault().toLanguageTag();

SystemProperties.set("persist.sys.locale", languageTag);

SystemProperties.set("persist.sys.language", "");

SystemProperties.set("persist.sys.country", "");

SystemProperties.set("persist.sys.localevar", "");

}

// The system server should never make non-oneway calls

Binder.setWarnOnBlocking(true);

// The system server should always load safe labels

PackageItemInfo.forceSafeLabels();

// Default to FULL within the system server.

SQLiteGlobal.sDefaultSyncMode = SQLiteGlobal.SYNC_MODE_FULL;

// Deactivate SQLiteCompatibilityWalFlags until settings provider is initialized

SQLiteCompatibilityWalFlags.init(null);

// Here we go!

Slog.i(TAG, "Entered the Android system server!");

final long uptimeMillis = SystemClock.elapsedRealtime();

EventLog.writeEvent(EventLogTags.BOOT_PROGRESS_SYSTEM_RUN, uptimeMillis);

if (!mRuntimeRestart) {

FrameworkStatsLog.write(FrameworkStatsLog.BOOT_TIME_EVENT_ELAPSED_TIME_REPORTED,

FrameworkStatsLog

.BOOT_TIME_EVENT_ELAPSED_TIME__EVENT__SYSTEM_SERVER_INIT_START,

uptimeMillis);

}

// In case the runtime switched since last boot (such as when

// the old runtime was removed in an OTA), set the system

// property so that it is in sync. We can't do this in

// libnativehelper's JniInvocation::Init code where we already

// had to fallback to a different runtime because it is

// running as root and we need to be the system user to set

// the property. http://b/11463182

SystemProperties.set("persist.sys.dalvik.vm.lib.2", VMRuntime.getRuntime().vmLibrary());

// Mmmmmm... more memory!

VMRuntime.getRuntime().clearGrowthLimit();

// Some devices rely on runtime fingerprint generation, so make sure

// we've defined it before booting further.

Build.ensureFingerprintProperty();

// Within the system server, it is an error to access Environment paths without

// explicitly specifying a user.

Environment.setUserRequired(true);

// Within the system server, any incoming Bundles should be defused

// to avoid throwing BadParcelableException.

BaseBundle.setShouldDefuse(true);

// Within the system server, when parceling exceptions, include the stack trace

Parcel.setStackTraceParceling(true);

// Ensure binder calls into the system always run at foreground priority.

BinderInternal.disableBackgroundScheduling(true);

// Increase the number of binder threads in system_server

BinderInternal.setMaxThreads(sMaxBinderThreads);

// Prepare the main looper thread (this thread).

android.os.Process.setThreadPriority(

android.os.Process.THREAD_PRIORITY_FOREGROUND);

android.os.Process.setCanSelfBackground(false);

Looper.prepareMainLooper();

Looper.getMainLooper().setSlowLogThresholdMs(

SLOW_DISPATCH_THRESHOLD_MS, SLOW_DELIVERY_THRESHOLD_MS);

SystemServiceRegistry.sEnableServiceNotFoundWtf = true;

// Initialize native services.

System.loadLibrary("android_servers");

// Allow heap / perf profiling.

initZygoteChildHeapProfiling();

// Debug builds - spawn a thread to monitor for fd leaks.

if (Build.IS_DEBUGGABLE) {

spawnFdLeakCheckThread();

}

// Check whether we failed to shut down last time we tried.

// This call may not return.

performPendingShutdown();

// Initialize the system context.

createSystemContext();

// Call per-process mainline module initialization.

ActivityThread.initializeMainlineModules();

// Create the system service manager.

mSystemServiceManager = new SystemServiceManager(mSystemContext);

mSystemServiceManager.setStartInfo(mRuntimeRestart,

mRuntimeStartElapsedTime, mRuntimeStartUptime);

LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);

// Prepare the thread pool for init tasks that can be parallelized

SystemServerInitThreadPool.start();

// Attach JVMTI agent if this is a debuggable build and the system property is set.

if (Build.IS_DEBUGGABLE) {

// Property is of the form "library_path=parameters".

String jvmtiAgent = SystemProperties.get("persist.sys.dalvik.jvmtiagent");

if (!jvmtiAgent.isEmpty()) {

int equalIndex = jvmtiAgent.indexOf('=');

String libraryPath = jvmtiAgent.substring(0, equalIndex);

String parameterList =

jvmtiAgent.substring(equalIndex + 1, jvmtiAgent.length());

// Attach the agent.

try {

Debug.attachJvmtiAgent(libraryPath, parameterList, null);

} catch (Exception e) {

Slog.e("System", "*************************************************");

Slog.e("System", "********** Failed to load jvmti plugin: " + jvmtiAgent);

}

}

}

} finally {

t.traceEnd(); // InitBeforeStartServices

}

// Setup the default WTF handler

RuntimeInit.setDefaultApplicationWtfHandler(SystemServer::handleEarlySystemWtf);

// Start services.

try {

t.traceBegin("StartServices");

startBootstrapServices(t);

startCoreServices(t);

startOtherServices(t);

} catch (Throwable ex) {

Slog.e("System", "******************************************");

Slog.e("System", "************ Failure starting system services", ex);

throw ex;

} finally {

t.traceEnd(); // StartServices

}

StrictMode.initVmDefaults(null);

if (!mRuntimeRestart && !isFirstBootOrUpgrade()) {

final long uptimeMillis = SystemClock.elapsedRealtime();

FrameworkStatsLog.write(FrameworkStatsLog.BOOT_TIME_EVENT_ELAPSED_TIME_REPORTED,

FrameworkStatsLog.BOOT_TIME_EVENT_ELAPSED_TIME__EVENT__SYSTEM_SERVER_READY,

uptimeMillis);

final long maxUptimeMillis = 60 * 1000;

if (uptimeMillis > maxUptimeMillis) {

Slog.wtf(SYSTEM_SERVER_TIMING_TAG,

"SystemServer init took too long. uptimeMillis=" + uptimeMillis);

}

}

// Diagnostic to ensure that the system is in a base healthy state. Done here as a common

// non-zygote process.

if (!VMRuntime.hasBootImageSpaces()) {

Slog.wtf(TAG, "Runtime is not running with a boot image!");

}

// Loop forever.

Looper.loop();

throw new RuntimeException("Main thread loop unexpectedly exited");

}

SystemServer.run() 是 Android Framework 中 system_server 进程的"主函数"，在 Zygote fork 出 system_server 之后被调用。它负责把 Android 运行所需的所有"系统服务"逐个创建、初始化并发布到 ServiceManager，最终进入 Looper 循环等待 Binder 事务。下面把 300 多行代码按功能阶段拆解说明。

──────────────────

初始化计时与 trace ────────────────── TimingsTraceAndSlog t = new TimingsTraceAndSlog(); t.traceBegin("InitBeforeStartServices");

开启 systrace 区间，方便性能分析工具抓取。

────────────────── 2. 记录启动信息到系统属性 + event log ────────────────── SystemProperties.set(SYSPROP_START_COUNT, ...); SystemProperties.set(SYSPROP_START_ELAPSED, ...); SystemProperties.set(SYSPROP_START_UPTIME, ...); EventLog.writeEvent(EventLogTags.SYSTEM_SERVER_START, ...);

mStartCount：本次开机 system_server 被重启的次数（0 代表第一次）。
mRuntimeStartElapsedTime / mRuntimeStartUptime：从开机到此刻的 elapsedRealTime / uptimeMillis。这些信息后续可被 dumpsys、bootstat、metrics 等抓取。

────────────────── 3. 检查并补全 persist.sys.timezone ────────────────── 如果 persist.sys.timezone 为空，则设为 "GMT"。

────────────────── 4. 将旧式语言属性迁移到 persist.sys.locale ────────────────── persist.sys.language / country / localevar 只在早期版本使用。

若仍残留，则以 Locale.getDefault().toLanguageTag() 生成新格式并存入 persist.sys.locale，然后把旧属性清空。

────────────────── 5. 全局行为开关 ────────────────── Binder.setWarnOnBlocking(true);

system_server 禁止进行阻塞式 Binder 调用，否则打印警告。

PackageItemInfo.forceSafeLabels();

强制所有包解析时加载"safe labels"，防止解析 apk 时引入不受信任的字符串。

SQLiteGlobal.sDefaultSyncMode = FULL;

系统进程使用 FULL sync，保证数据安全。

SQLiteCompatibilityWalFlags.init(null);

先禁用 WAL-compat flag，等 settings provider 起来后再决定。

────────────────── 6. 系统级环境准备 ────────────────── Slog.i(TAG, "Entered the Android system server!");

打 log 供 logcat 过滤。

SystemProperties.set("persist.sys.dalvik.vm.lib.2", VMRuntime.getRuntime().vmLibrary());

把当前运行时 libart.so / libdvm.so 写回属性，保持与 native 侧一致。

VMRuntime.getRuntime().clearGrowthLimit();

取消 Dalvik/ART 的 heap growth limit，允许 system_server 用更多 RAM。

Build.ensureFingerprintProperty();

确保 ro.build.fingerprint 已生成。

Environment.setUserRequired(true);

以后所有访问 Environment 路径必须指定 user handle，避免 user 0 隐式依赖。

BaseBundle.setShouldDefuse(true); Parcel.setStackTraceParceling(true); BinderInternal.disableBackgroundScheduling(true); BinderInternal.setMaxThreads(sMaxBinderThreads);

防止恶意 Bundle、异常序列化泄露，确保所有 Binder 调用以最高优先级运行，并把 Binder 线程池上限调到 31/63（视版本）。

────────────────── 7. 主线程 Looper 初始化 ────────────────── Looper.prepareMainLooper(); Looper.getMainLooper().setSlowLogThresholdMs(...);

system_server 的主线程变为 "ActivityManager" 线程。

────────────────── 8. 加载 native 库 & 调试功能 ────────────────── System.loadLibrary("android_servers");

加载 libandroid_servers.so，内含 SurfaceFlinger、Sensor、Audio 等 native 服务 JNI。

initZygoteChildHeapProfiling();

如果系统属性 ro.config.hw_perf 等开启，则启动 heap profile。

if (Build.IS_DEBUGGABLE) spawnFdLeakCheckThread();

debug 版会起子线程每 30 s 扫描 /proc/self/fd，发现泄漏就 dump。

performPendingShutdown();

检查 /data/system/shutdown-request.dat，如果上次关机失败则直接关机或重启。

────────────────── 9. 创建系统 Context 与 ServiceManager ────────────────── createSystemContext();

创建 system Context（package = "android"，theme = system），加载 framework-res.apk。

ActivityThread.initializeMainlineModules();

把 Mainline 模块（如 ART 模块、Statsd、Media 组件等）提前初始化。

mSystemServiceManager = new SystemServiceManager(mSystemContext); LocalServices.addService(SystemServiceManager.class, mSystemServiceManager); SystemServerInitThreadPool.start();

SystemServiceManager 负责以后 startService 的生命周期；并行线程池用于加速初始化。

────────────────── 10. 可选 JVMTI agent ────────────────── debuggable 版本如果 persist.sys.dalvik.jvmtiagent 指定了 agent，则 attach。

t.traceEnd(); // InitBeforeStartServices

────────────────── 11. 设置默认 WTF handler ────────────────── RuntimeInit.setDefaultApplicationWtfHandler(SystemServer::handleEarlySystemWtf);

捕获系统早期 crash，避免直接 kill system_server。

────────────────── 12. 启动三大类服务 ────────────────── t.traceBegin("StartServices"); startBootstrapServices(t); // 基础、必须在早期启动 startCoreServices(t); // 平台核心服务 startOtherServices(t); // 剩余所有服务 t.traceEnd();

(下面列出典型包含的服务，具体版本有差异)

12.1 startBootstrapServices()

Installer (增量安装 native 侧)
DeviceIdentifiersPolicyService
ActivityManagerService (ATM + AMS)
PowerManagerService
RecoverySystemService
LightsService
DisplayManagerService
PackageManagerService
UserManagerService
OverlayManagerService
SensorPrivacyService
(P)SensorService
(P)BluetoothService
...

12.2 startCoreServices()

BatteryService
UsageStatsService
WebViewUpdateService
BinderCallsStatsService
...

12.3 startOtherServices()

AccountManagerService
ContentService
VibratorService
AlarmManagerService
InputManagerService
WindowManagerService
BluetoothService (部分版本移到 bootstrap)
TelecomLoaderService
ConnectivityService
NetworkManagementService
NetworkStatsService
NetworkPolicyManagerService
WifiService
WifiScanningService
AudioService
CameraService
TrustManagerService
JobSchedulerService
ShortcutService
NotificationManagerService
DevicePolicyManagerService
StatusBarManagerService
ClipboardService
NetworkTimeUpdateService
CommonTimeManagementService
InputMethodManagerService
TextServicesManagerService
...（总计 100+）

每个服务通过 SystemServiceManager.startService() 或 ServiceManager.addService() 注册。细节见 SystemServer.java 的各 start*Services() 方法，此处略。

────────────────── 13. StrictMode 默认策略 ────────────────── StrictMode.initVmDefaults(null);

system_server 自己也要受 StrictMode 检查，防止系统代码违规。

────────────────── 14. 记录系统就绪时间 & 诊断 ────────────────── if (!mRuntimeRestart && !isFirstBootOrUpgrade()) { FrameworkStatsLog.write(... SYSTEM_SERVER_READY ...); if (uptimeMillis > 60 s) Slog.wtf ... }

如果非重启且非 OTA，则把 "system_server 从 init 到 ready" 耗时发送给 statsd。
超过 60 s 打 WTF（系统启动异常慢）。

if (!VMRuntime.hasBootImageSpaces()) Slog.wtf ...

如果当前 ART 没有 boot image，则系统性能会严重下降，打 WTF。

────────────────── 15. 进入主循环 ────────────────── Looper.loop();

system_server 主线程开始处理 Binder、Handler 消息队列，永不返回。
如果 loop() 意外退出，抛 RuntimeException，SystemServer 会触发重启 UI 或直接重启系统。

────────────────── 小结 ────────────────── run() 的工作可以概括为：

记录启动信息
设置系统属性、时区、locale、SQLite、Binder、环境等全局状态
创建 system context 和 SystemServiceManager
并行/顺序地启动 100+ 系统服务
进入 Looper，把线程变成 Binder 服务端，永远处理事务

这些步骤完成后，Android Framework 层才算真正"跑起来"，应用进程才能通过 Binder 调用 AMS、WMS、PKMS 等系统服务。