Android 5.1 SystemServer SystemService 各个系统Manager

一、SystemServer

Zygote如何启动SystemServer就不分析了，主要分析下java层：

先看下主函数

[java] view plain copy

print ?

1. public static void main(String[] args) {  
2.     new SystemServer().run();  
3. }  

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

下面我们看run函数里面的java service的启动：

[java] view plain copy

print ?

1. mSystemServiceManager = new SystemServiceManager(mSystemContext);  
2. LocalServices.addService(SystemServiceManager.class, mSystemServiceManager);  
3.   
4. // Start services.  
5. try {  
6.     startBootstrapServices();  
7.     startCoreServices();  
8.     startOtherServices();  
9. } catch (Throwable ex) {  
10.     Slog.e("System", "******************************************");  
11.     Slog.e("System", "************ Failure starting system services", ex);  
12.     throw ex;  
13. }  

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

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

SystemServiceManager这个类只是管理各个service，用SystemServiceManager启动service的时候，会把service加入自己的链表。并且调用service的onStart函数。

[java] view plain copy

print ?

1. public <T extends SystemService> T startService(Class<T> serviceClass) {  
2.     final String name = serviceClass.getName();  
3.     Slog.i(TAG, "Starting " + name);  
4.   
5.     // Create the service.  
6.     if (!SystemService.class.isAssignableFrom(serviceClass)) {  
7.         throw new RuntimeException("Failed to create " + name  
8.                 + ": service must extend " + SystemService.class.getName());  
9.     }  
10.     final T service;  
11.     try {  
12.         Constructor<T> constructor = serviceClass.getConstructor(Context.class);  
13.         service = constructor.newInstance(mContext);  
14.     } catch (InstantiationException ex) {  
15.         throw new RuntimeException("Failed to create service " + name  
16.                 + ": service could not be instantiated", ex);  
17.     } catch (IllegalAccessException ex) {  
18.         throw new RuntimeException("Failed to create service " + name  
19.                 + ": service must have a public constructor with a Context argument", ex);  
20.     } catch (NoSuchMethodException ex) {  
21.         throw new RuntimeException("Failed to create service " + name  
22.                 + ": service must have a public constructor with a Context argument", ex);  
23.     } catch (InvocationTargetException ex) {  
24.         throw new RuntimeException("Failed to create service " + name  
25.                 + ": service constructor threw an exception", ex);  
26.     }  
27.   
28.     // Register it.  
29.     mServices.add(service);//加入链表  
30.   
31.     // Start it.  
32.     try {  
33.         service.onStart();//调用service的onStart函数  
34.     } catch (RuntimeException ex) {  
35.         throw new RuntimeException("Failed to start service " + name  
36.                 + ": onStart threw an exception", ex);  
37.     }  
38.     return service;  
39. }  

    public <T extends SystemService> T startService(Class<T> serviceClass) {
        final String name = serviceClass.getName();
        Slog.i(TAG, "Starting " + name);

        // Create the service.
        if (!SystemService.class.isAssignableFrom(serviceClass)) {
            throw new RuntimeException("Failed to create " + name
                    + ": service must extend " + SystemService.class.getName());
        }
        final T service;
        try {
            Constructor<T> constructor = serviceClass.getConstructor(Context.class);
            service = constructor.newInstance(mContext);
        } catch (InstantiationException ex) {
            throw new RuntimeException("Failed to create service " + name
                    + ": service could not be instantiated", ex);
        } catch (IllegalAccessException ex) {
            throw new RuntimeException("Failed to create service " + name
                    + ": service must have a public constructor with a Context argument", ex);
        } catch (NoSuchMethodException ex) {
            throw new RuntimeException("Failed to create service " + name
                    + ": service must have a public constructor with a Context argument", ex);
        } catch (InvocationTargetException ex) {
            throw new RuntimeException("Failed to create service " + name
                    + ": service constructor threw an exception", ex);
        }

        // Register it.
        mServices.add(service);//加入链表

        // Start it.
        try {
            service.onStart();//调用service的onStart函数
        } catch (RuntimeException ex) {
            throw new RuntimeException("Failed to start service " + name
                    + ": onStart threw an exception", ex);
        }
        return service;
    }

SystemServer每执行到一个阶段都会调用SystemServiceManager的startBootPhase函数

[java] view plain copy

print ?

1. mActivityManagerService = mSystemServiceManager.startService(  
2.         ActivityManagerService.Lifecycle.class).getService();  
3. mActivityManagerService.setSystemServiceManager(mSystemServiceManager);  
4. mActivityManagerService.setInstaller(installer);  
5.   
6. // Power manager needs to be started early because other services need it.  
7. // Native daemons may be watching for it to be registered so it must be ready  
8. // to handle incoming binder calls immediately (including being able to verify  
9. // the permissions for those calls).  
10. mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);  
11.   
12. // Now that the power manager has been started, let the activity manager  
13. // initialize power management features.  
14. mActivityManagerService.initPowerManagement();  
15.   
16. // Display manager is needed to provide display metrics before package manager  
17. // starts up.  
18. mDisplayManagerService = mSystemServiceManager.startService(DisplayManagerService.class);  
19.   
20. // We need the default display before we can initialize the package manager.  
21. mSystemServiceManager.startBootPhase(SystemService.PHASE_WAIT_FOR_DEFAULT_DISPLAY);  

        mActivityManagerService = mSystemServiceManager.startService(
                ActivityManagerService.Lifecycle.class).getService();
        mActivityManagerService.setSystemServiceManager(mSystemServiceManager);
        mActivityManagerService.setInstaller(installer);

        // Power manager needs to be started early because other services need it.
        // Native daemons may be watching for it to be registered so it must be ready
        // to handle incoming binder calls immediately (including being able to verify
        // the permissions for those calls).
        mPowerManagerService = mSystemServiceManager.startService(PowerManagerService.class);

        // Now that the power manager has been started, let the activity manager
        // initialize power management features.
        mActivityManagerService.initPowerManagement();

        // Display manager is needed to provide display metrics before package manager
        // starts up.
        mDisplayManagerService = mSystemServiceManager.startService(DisplayManagerService.class);

        // We need the default display before we can initialize the package manager.
        mSystemServiceManager.startBootPhase(SystemService.PHASE_WAIT_FOR_DEFAULT_DISPLAY);

我们下面看下SystemServiceManager的startBootPhase函数，它会把mServices中的service取出来，调用onBootPhase函数

[java] view plain copy

print ?

1. public void startBootPhase(final int phase) {  
2.     if (phase <= mCurrentPhase) {  
3.         throw new IllegalArgumentException("Next phase must be larger than previous");  
4.     }  
5.     mCurrentPhase = phase;  
6.   
7.     Slog.i(TAG, "Starting phase " + mCurrentPhase);  
8.   
9.     final int serviceLen = mServices.size();  
10.     for (int i = 0; i < serviceLen; i++) {  
11.         final SystemService service = mServices.get(i);  
12.         try {  
13.             service.onBootPhase(mCurrentPhase);  
14.         } catch (Exception ex) {  
15.             throw new RuntimeException("Failed to boot service "  
16.                     + service.getClass().getName()  
17.                     + ": onBootPhase threw an exception during phase "  
18.                     + mCurrentPhase, ex);  
19.         }  
20.     }  
21. }  

    public void startBootPhase(final int phase) {
        if (phase <= mCurrentPhase) {
            throw new IllegalArgumentException("Next phase must be larger than previous");
        }
        mCurrentPhase = phase;

        Slog.i(TAG, "Starting phase " + mCurrentPhase);

        final int serviceLen = mServices.size();
        for (int i = 0; i < serviceLen; i++) {
            final SystemService service = mServices.get(i);
            try {
                service.onBootPhase(mCurrentPhase);
            } catch (Exception ex) {
                throw new RuntimeException("Failed to boot service "
                        + service.getClass().getName()
                        + ": onBootPhase threw an exception during phase "
                        + mCurrentPhase, ex);
            }
        }
    }

二、SystemService

我们再来SystemService这个类，这个类一般是一些系统service来继承这个类

先看看PowerManagerService

[java] view plain copy

print ?

1. public final class PowerManagerService extends SystemService  
2.         implements Watchdog.Monitor {  

public final class PowerManagerService extends SystemService
        implements Watchdog.Monitor {

其中实现了onStart和onBootPhase函数

扫描二维码关注公众号，回复： 592827 查看本文章

[java] view plain copy

print ?

1. @Override  
2. public void onStart() {  
3.     publishBinderService(Context.POWER_SERVICE, new BinderService());  
4.     publishLocalService(PowerManagerInternal.class, new LocalService());  
5.   
6.     Watchdog.getInstance().addMonitor(this);  
7.     Watchdog.getInstance().addThread(mHandler);  
8. }  
9.   
10. @Override  
11. public void onBootPhase(int phase) {  
12.     synchronized (mLock) {  
13.         if (phase == PHASE_BOOT_COMPLETED) {  
14.             final long now = SystemClock.uptimeMillis();  
15.             mBootCompleted = true;  
16.             mDirty |= DIRTY_BOOT_COMPLETED;  
17.             userActivityNoUpdateLocked(  
18.                     now, PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, Process.SYSTEM_UID);  
19.             updatePowerStateLocked();  
20.         }  
21.     }  
22. }  

    @Override
    public void onStart() {
        publishBinderService(Context.POWER_SERVICE, new BinderService());
        publishLocalService(PowerManagerInternal.class, new LocalService());

        Watchdog.getInstance().addMonitor(this);
        Watchdog.getInstance().addThread(mHandler);
    }

    @Override
    public void onBootPhase(int phase) {
        synchronized (mLock) {
            if (phase == PHASE_BOOT_COMPLETED) {
                final long now = SystemClock.uptimeMillis();
                mBootCompleted = true;
                mDirty |= DIRTY_BOOT_COMPLETED;
                userActivityNoUpdateLocked(
                        now, PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, Process.SYSTEM_UID);
                updatePowerStateLocked();
            }
        }
    }

其中publishBinderService函数是SystemService中的函数，最后是调用了ServiceManager.addService。

[java] view plain copy

print ?

1. protected final void publishBinderService(String name, IBinder service) {  
2.     publishBinderService(name, service, false);  
3. }  
4.   
5. /** 
6.  * Publish the service so it is accessible to other services and apps. 
7.  */  
8. protected final void publishBinderService(String name, IBinder service,  
9.         boolean allowIsolated) {  
10.     ServiceManager.addService(name, service, allowIsolated);  
11. }  

    protected final void publishBinderService(String name, IBinder service) {
        publishBinderService(name, service, false);
    }

    /**
     * Publish the service so it is accessible to other services and apps.
     */
    protected final void publishBinderService(String name, IBinder service,
            boolean allowIsolated) {
        ServiceManager.addService(name, service, allowIsolated);
    }

三、ServiceManager

而ServiceManager 这个类，是java层用来和serviceManager进程通信的。

[java] view plain copy

print ?

1. public final class ServiceManager {  
2.     private static final String TAG = "ServiceManager";  
3.   
4.     private static IServiceManager sServiceManager;  
5.     private static HashMap<String, IBinder> sCache = new HashMap<String, IBinder>();  
6.   
7.     private static IServiceManager getIServiceManager() {  
8.         if (sServiceManager != null) {  
9.             return sServiceManager;  
10.         }  
11.   
12.         // Find the service manager  
13.         sServiceManager = ServiceManagerNative.asInterface(BinderInternal.getContextObject());  
14.         return sServiceManager;  
15.     }  
16.   
17.     /** 
18.      * Returns a reference to a service with the given name. 
19.      *  
20.      * @param name the name of the service to get 
21.      * @return a reference to the service, or <code>null</code> if the service doesn't exist 
22.      */  
23.     public static IBinder getService(String name) {  
24.         try {  
25.             IBinder service = sCache.get(name);  
26.             if (service != null) {  
27.                 return service;  
28.             } else {  
29.                 return getIServiceManager().getService(name);  
30.             }  
31.         } catch (RemoteException e) {  
32.             Log.e(TAG, "error in getService", e);  
33.         }  
34.         return null;  
35.     }  
36.   
37.     /** 
38.      * Place a new @a service called @a name into the service 
39.      * manager. 
40.      *  
41.      * @param name the name of the new service 
42.      * @param service the service object 
43.      */  
44.     public static void addService(String name, IBinder service) {  
45.         try {  
46.             getIServiceManager().addService(name, service, false);  
47.         } catch (RemoteException e) {  
48.             Log.e(TAG, "error in addService", e);  
49.         }  
50.     }  

public final class ServiceManager {
    private static final String TAG = "ServiceManager";

    private static IServiceManager sServiceManager;
    private static HashMap<String, IBinder> sCache = new HashMap<String, IBinder>();

    private static IServiceManager getIServiceManager() {
        if (sServiceManager != null) {
            return sServiceManager;
        }

        // Find the service manager
        sServiceManager = ServiceManagerNative.asInterface(BinderInternal.getContextObject());
        return sServiceManager;
    }

    /**
     * Returns a reference to a service with the given name.
     * 
     * @param name the name of the service to get
     * @return a reference to the service, or <code>null</code> if the service doesn't exist
     */
    public static IBinder getService(String name) {
        try {
            IBinder service = sCache.get(name);
            if (service != null) {
                return service;
            } else {
                return getIServiceManager().getService(name);
            }
        } catch (RemoteException e) {
            Log.e(TAG, "error in getService", e);
        }
        return null;
    }

    /**
     * Place a new @a service called @a name into the service
     * manager.
     * 
     * @param name the name of the new service
     * @param service the service object
     */
    public static void addService(String name, IBinder service) {
        try {
            getIServiceManager().addService(name, service, false);
        } catch (RemoteException e) {
            Log.e(TAG, "error in addService", e);
        }
    }

四、系统的各个Manager

再来看看ContextImpl里面对各个Manager的注册，下面是PMS的注册

[java] view plain copy

print ?

1. registerService(POWER_SERVICE, new ServiceFetcher() {  
2.         public Object createService(ContextImpl ctx) {  
3.             IBinder b = ServiceManager.getService(POWER_SERVICE);  
4.             IPowerManager service = IPowerManager.Stub.asInterface(b);  
5.             if (service == null) {  
6.                 Log.wtf(TAG, "Failed to get power manager service.");  
7.             }  
8.             return new PowerManager(ctx.getOuterContext(),  
9.                     service, ctx.mMainThread.getHandler());  
10.         }});  

        registerService(POWER_SERVICE, new ServiceFetcher() {
                public Object createService(ContextImpl ctx) {
                    IBinder b = ServiceManager.getService(POWER_SERVICE);
                    IPowerManager service = IPowerManager.Stub.asInterface(b);
                    if (service == null) {
                        Log.wtf(TAG, "Failed to get power manager service.");
                    }
                    return new PowerManager(ctx.getOuterContext(),
                            service, ctx.mMainThread.getHandler());
                }});

再来看看getSystemService，比如获取PowerManager等

[java] view plain copy

print ?

1. @Override  
2. public Object getSystemService(String name) {  
3.     ServiceFetcher fetcher = SYSTEM_SERVICE_MAP.get(name);  
4.     return fetcher == null ? null : fetcher.getService(this);  
5. }  

    @Override
    public Object getSystemService(String name) {
        ServiceFetcher fetcher = SYSTEM_SERVICE_MAP.get(name);
        return fetcher == null ? null : fetcher.getService(this);
    }

下面ServiceFetcher 中createService就是上面在注册各个Manager的时候定义的。

[java] view plain copy

print ?

1. /*package*/ static class ServiceFetcher {  
2.     int mContextCacheIndex = -1;  
3.   
4.     /** 
5.      * Main entrypoint; only override if you don't need caching. 
6.      */  
7.     public Object getService(ContextImpl ctx) {  
8.         ArrayList<Object> cache = ctx.mServiceCache;  
9.         Object service;  
10.         synchronized (cache) {  
11.             if (cache.size() == 0) {  
12.                 // Initialize the cache vector on first access.  
13.                 // At this point sNextPerContextServiceCacheIndex  
14.                 // is the number of potential services that are  
15.                 // cached per-Context.  
16.                 for (int i = 0; i < sNextPerContextServiceCacheIndex; i++) {  
17.                     cache.add(null);  
18.                 }  
19.             } else {  
20.                 service = cache.get(mContextCacheIndex);  
21.                 if (service != null) {  
22.                     return service;  
23.                 }  
24.             }  
25.             service = createService(ctx);  
26.             cache.set(mContextCacheIndex, service);  
27.             return service;  
28.         }  
29.     }  
30.   
31.     /** 
32.      * Override this to create a new per-Context instance of the 
33.      * service.  getService() will handle locking and caching. 
34.      */  
35.     public Object createService(ContextImpl ctx) {  
36.         throw new RuntimeException("Not implemented");  
37.     }  
38. }