Systemserver service and servicemanager service analysis

1 SystemServer Service analysis

SystemServer yes zygote The first one to start Android Service process , The main work is as follows ：
(1) Create all core services of the system
(2) Add services to ServiceManager in
(3) Initialize service

1.1 SystemServer Services started

(1)power
PowerManagerService: Power management
BatteryService: Battery service
(2)ActivityManagerService
Activity management service
(3)PackageManagerService
Package management service , And bottom installd Establish communication
(4)WindowManagerService
Window management service , And surfaceflinger Service interaction
(5)TelephonyRegistry
telephony support
(6)ContentService
Data exchange between processes
(7)Sensor
LightsService: Light sense
VibratorService: Vibration
(8)Network
NetworkManagementService: Mobile network management services
NetworkStatsService: Mobile network status service
WifiP2pService:p2p service
WifiService:wifi service
ConnectivityService: Network connection status service
(9)BluetoothService
Bluetooth service

1.2 SystemServer Start process

(1)SystemServer.main()
(2)dalvik.set()
(3)System.loadlibrary("android_servers");
(4)nativeInit()
(5)initAndLoop()
Start various services of the system , Add services to ServiceManager in .

2 ServiceManager Service analysis

2.1 ServiceManager Service Overview

(1) Service process , yes android One of the core services of the system
(2) System service management ： Manage the services added to the system by the system and Applications
(3) Query for services ： Respond to client Request and return the corresponding service
Android If an application wants to get a system service , This system service needs to be added to ServiceManager in . If the service exits abnormally several times in a row , The system will restart . If the service is restarted , The system will restart zygote,surfaceflinger,media Etc .

2.2 ServiceManager When was it created ?

ServiceManager By init Process by parsing init.rc File , The corresponding executable program /system/bin/servicemanager, The corresponding source file is service_manager.c.

service servicemanager /system/bin/servicemanager
    class core
    user system
    group system
    critical
    onrestart restart healthd
    onrestart restart zygote
    onrestart restart media
    onrestart restart surfaceflinger
    onrestart restart drm

2.3 ServiceManager The boot process

(1) open binder
ServiceManager be based on Binder Mechanism realization
binder_open()
open("/dev/binder")
mmap()
(2)binder_become_context_manager()
(3) Cyclic reception binder news
Received binder Message type ： Add service , Query services and obtain services
adopt binder_loop() To receive messages sent by other processes binder news
(4) Handle binder news
adopt svcmgr_handler() Handle those sent by other processes binder news

2.4 ServiceManager management service

 

chart 1 ServiceManager management service
(1) System or Android The application process sends a request to add system services , adopt binder Interprocess communication to ServiceManager Process processing , Then check the permissions of the process that initiated the request , Then check whether the service already exists , If there is a direct return ; If it doesn't exist , Add this service to Service List in .
(2) This service is also obtained through binder Interprocess communication to ServiceManager Process processing , Inquire about Service List Find out what to do Service, Then return .