SystemServer进程源码分析之一

1, 基本概念

SystemServer是三大核心步骤中的最后一个,主要是各种服务的注册和启动。SystemServer进程由Zygote进程启动。zygoteInit的startSystemServer部分方法如下,

String args[] = { // SystemServer服务进程的信息
            "--setuid=1000", // uid
            "--setgid=1000", // gid
            "--setgroups=1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,1018,1021,1032,3001,3002,3003,3006,3007",
            "--capabilities=" + capabilities + "," + capabilities,
            "--nice-name=system_server", // 进程名
            "--runtime-args",
            "com.android.server.SystemServer", // 包名
        };

在Zygote文章中已经分析了SystemServer进程的启动流程,在此就不多论述了,直接看SystemServer的main方法。

2, SystemServer

SystemServer的main方法如下,

public static void main(String[] args) {
        new SystemServer().run();
    }

Main函数很简单,仅仅构造一个SystemServer对象,然后调用run方法

run方法比较长,还是看大体步骤

1,调整时间

if (System.currentTimeMillis() < EARLIEST_SUPPORTED_TIME) {
            Slog.w(TAG, "System clock is before 1970; setting to 1970.");
            SystemClock.setCurrentTimeMillis(EARLIEST_SUPPORTED_TIME);
        }

2,设置系统相关属性

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", "");
        }
public static void main(String[] args) {
        new SystemServer().run();
}

3,设置环境

VMRuntime.getRuntime().setTargetHeapUtilization(0.8f); // 虚拟机堆栈的大小
        Build.ensureFingerprintProperty(); // 初始化binder
        Environment.setUserRequired(true);
        BinderInternal.disableBackgroundScheduling(true);

        // Prepare the main looper thread (this thread).
        android.os.Process.setThreadPriority(       // Binder,消息机制
                android.os.Process.THREAD_PRIORITY_FOREGROUND);
        android.os.Process.setCanSelfBackground(false);
        Looper.prepareMainLooper();

        // Initialize native services.
        System.loadLibrary("android_servers"); // 加载JNI运行库

4,创建进程上下文

createSystemContext();

5,创建SystemServiceManager

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

6,启动各种服务

  // Start services.
        try {
            startBootstrapServices();
            startCoreServices();
            startOtherServices();
        } catch (Throwable ex) {
            Slog.e("System", "******************************************");
            Slog.e("System", "************ Failure starting system services", ex);
            throw ex;
        }

7,开始循环处理消息。

Looper.loop();

3, 启动各种服务

服务分三类启动:

3.1 startBootstrapServices

ActivityManagerService	PowerManagerService	LightsService
DisplayManagerService	RegionalizationService	PackageManagerService
SensorService

3.2 startCoreServices

BatteryService

UsageStatsService

WebViewUpdateService

3.3 startOtherServices

SchedulingPolicyService	TelecomLoaderService	telephonyRegistry
CameraService	AccountManagerService	ContentService
VibratorService	ConsumerIrService	AlarmManagerService
Watchdog	InputManagerService	WindowManagerService
BluetoothService	InputMethodManagerService	MountService
UiModeManagerService	LockSettingsService	DeviceIdleController
StatusBarManagerService	ClipboardService	WifiP2pService
NetworkScoreService	NetworkStatsService	WifiService
WifiScanningService	RttService	EthernetService
ConnectivityService	NsdService	UpdateLockService
LocationManagerService	CountryDetectorService	SearchManagerService
DropBoxManagerService	WallpaperManagerService	AudioService
DockObserver	WiredAccessoryManager	MidiService
UsbService	SerialService	TwilightService
JobSchedulerService	BackupManagerService	AppWidgetService
GestureLauncherService	DiskStatsService	SamplingProfilerService
CertBlacklister	DreamManagerService	AssetAtlasService
PrintManagerService	MediaSessionService	HdmiControlService
MediaRouterService	TrustManagerService	FingerprintService
LauncherAppsService	MmsServiceBroker

AccessibilityManagerService   PersistentDataBlockService   DevicePolicyManagerService

NetworkManagementService  TextServicesManagerService  NetworkPolicyManagerService

NotificationManagerService   DeviceStorageMonitorService  VoiceInteractionManagerService

NetworkTimeUpdateService   CommonTimeManagementService  GraphicsStatsService

RestrictionsManagerService   TvInputManagerService      MediaProjectionManagerService

果然,一切皆服务啊!

4,小结

SystemServer进程是android中一个很重要的进程由Zygote进程启动

SystemServer进程主要用于启动系统中的服务