PowerManagerService流程分析
一、PowerManagerService简介
PowerManagerService主要服务Android系统电源管理工作，这样讲比较笼统，就具体细节上大致可以认为PowerManagerService集中处理用户活动（如点击屏幕，按电源键等）、电量变化、用户设置（如在Setting中设置省电模式，飞行模式）、插拔充电器（无线冲，有线冲）等。当发生以上事件时，PowerManagerService都要进行各种状态的更新，以下把PMS作为PowerManagerService的简称
二、PowerManagerService启动流程
2.1、PMS启动
// 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);
.
.
.
try {
// TODO: use boot phase
mPowerManagerService.systemReady(mActivityManagerService.getAppOpsService());
} catch (Throwable e) {
reportWtf("making Power Manager Service ready", e);
}
2.2、SystemServiceManager.startService()
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);
30
31 // Start it.
32 try {
33 service.onStart();
34 } catch (RuntimeException ex) {
35 throw new RuntimeException("Failed to start service " + name
36 + ": onStart threw an exception", ex);
37 }
38 return service;
39 }
在Android5.0以后SystemServer启动服务的方式发生了改变，在Android4.4以前SystemServer通过new方法创建服务的对象，并把服务注册到SystemManager中；Android5.0以后SystemServer通过SystemServiceManager.startService来启动服务，主要通过反射的方式获取服务的构造方法，并创建服务对象；最后调用服务重写的onStart（）方法。
说明：Android5.0以后所有服务都实现SystemService接口，这样方法服务的统一管理。
2.3 、PMS构造方法
public PowerManagerService(Context context) {
super(context);
mContext = context;
//启动一个线程，创建一个handler，handler发送的消息由该线程来处理
mHandlerThread = new ServiceThread(TAG,
Process.THREAD_PRIORITY_DISPLAY, false /*allowIo*/);
mHandlerThread.start();
mHandler = new PowerManagerHandler(mHandlerThread.getLooper());
synchronized (mLock) {
//创建两个suspendBlocker对象，获取suspendblocker防止cpu进去休眠
mWakeLockSuspendBlocker = createSuspendBlockerLocked("PowerManagerService.WakeLocks");
mDisplaySuspendBlocker = createSuspendBlockerLocked("PowerManagerService.Display");
mDisplaySuspendBlocker.acquire();
mHoldingDisplaySuspendBlocker = true;
mHalAutoSuspendModeEnabled = false;
mHalInteractiveModeEnabled = true;
mWakefulness = WAKEFULNESS_AWAKE;
//初始化电源相关设置，这些方法通过jni调动native方法
nativeInit();
nativeSetAutoSuspend(false);
nativeSetInteractive(true);
nativeSetFeature(POWER_FEATURE_DOUBLE_TAP_TO_WAKE, 0);
}
}
2.4、OnStart()方法
1 @Override
2 public void onStart() {
3 //BinderService继承IPowerManager.Stub，其实就是PowerManager的服务端
4 //这里其实就是把BinderService对象注册到ServiceManager中
5 publishBinderService(Context.POWER_SERVICE, new BinderService());
6 publishLocalService(PowerManagerInternal.class, new LocalService());
7
8 //加入Watchdog监听
9 Watchdog.getInstance().addMonitor(this);
10 Watchdog.getInstance().addThread(mHandler);
11 }
2.5、systemReady()方法
public void systemReady(IAppOpsService appOps) {
synchronized (mLock) {
mSystemReady = true;
mAppOps = appOps;
mDreamManager = getLocalService(DreamManagerInternal.class);
mDisplayManagerInternal = getLocalService(DisplayManagerInternal.class);
mPolicy = getLocalService(WindowManagerPolicy.class);
mBatteryManagerInternal = getLocalService(BatteryManagerInternal.class);
PowerManager pm = (PowerManager) mContext.getSystemService(Context.POWER_SERVICE);
//最大、最小、默认的屏幕亮超时时间
mScreenBrightnessSettingMinimum = pm.getMinimumScreenBrightnessSetting();
mScreenBrightnessSettingMaximum = pm.getMaximumScreenBrightnessSetting();
mScreenBrightnessSettingDefault = pm.getDefaultScreenBrightnessSetting();
//传感器相关，传感器检查到外部事件可以通过发送消息到mHandler的消息队列中处理
SensorManager sensorManager = new SystemSensorManager(mContext, mHandler.getLooper());
// The notifier runs on the system server's main looper so as not to interfere
// with the animations and other critical functions of the power manager.
mBatteryStats = BatteryStatsService.getService();
//注意上面的注释，notifier运行在system server的主线程中，并且参数中传入了一个SuspendBlocker对象，应该发送通知的时候需要点亮屏幕
mNotifier = new Notifier(Looper.getMainLooper(), mContext, mBatteryStats,
mAppOps, createSuspendBlockerLocked("PowerManagerService.Broadcasts"),
mPolicy);
//无线充电器相关，参数中传入了sensorManager，并且参数中传入了一个SuspendBlocker对象，也是为了有外部事件发生时点亮屏幕
mWirelessChargerDetector = new WirelessChargerDetector(sensorManager,
createSuspendBlockerLocked("PowerManagerService.WirelessChargerDetector"),
mHandler);
//ContentObserver对象，用来监听电源相关设置的改变
mSettingsObserver = new SettingsObserver(mHandler);
mLightsManager = getLocalService(LightsManager.class);
mAttentionLight = mLightsManager.getLight(LightsManager.LIGHT_ID_ATTENTION);
// Initialize display power management.
mDisplayManagerInternal.initPowerManagement(
mDisplayPowerCallbacks, mHandler, sensorManager);
// Register for broadcasts from other components of the system.
//注册一些广播监听器，如电量变化、用户切换(多用户模式，一般手机就是单用户)
IntentFilter filter = new IntentFilter();
filter.addAction(Intent.ACTION_BATTERY_CHANGED);
filter.setPriority(IntentFilter.SYSTEM_HIGH_PRIORITY);
mContext.registerReceiver(new BatteryReceiver(), filter, null, mHandler);
filter = new IntentFilter();
filter.addAction(Intent.ACTION_DREAMING_STARTED);
filter.addAction(Intent.ACTION_DREAMING_STOPPED);
mContext.registerReceiver(new DreamReceiver(), filter, null, mHandler);
filter = new IntentFilter();
filter.addAction(Intent.ACTION_USER_SWITCHED);
mContext.registerReceiver(new UserSwitchedReceiver(), filter, null, mHandler);
filter = new IntentFilter();
filter.addAction(Intent.ACTION_DOCK_EVENT);
mContext.registerReceiver(new DockReceiver(), filter, null, mHandler);
// Register for settings changes.
//监听系统中对电源的设置，如开启省电模式、默认休眠超时时间、屏幕亮度、充电是否亮屏等等
final ContentResolver resolver = mContext.getContentResolver();
resolver.registerContentObserver(Settings.Secure.getUriFor(
Settings.Secure.SCREENSAVER_ENABLED),
false, mSettingsObserver, UserHandle.USER_ALL);
.......
.......
.......
// Go.
//读取资源文件中电源相关设置
readConfigurationLocked();
//更新设置中对电源的相关设置
updateSettingsLocked();
mDirty |= DIRTY_BATTERY_STATE;
//更新电源状态，这里统一处理了所有的状态更新，该方法会被频繁调用
updatePowerStateLocked();
}
}
2.6、updatePowerStateLocked()方法
1 private void updatePowerStateLocked() {
2 if (!mSystemReady || mDirty == 0) {
3 return;
4 }
5 if (!Thread.holdsLock(mLock)) {
6 Slog.wtf(TAG, "Power manager lock was not held when calling updatePowerStateLocked");
7 }
8
9 Trace.traceBegin(Trace.TRACE_TAG_POWER, "updatePowerState");
10 try {
11 // Phase 0: Basic state updates.
12 updateIsPoweredLocked(mDirty);
13 //设置DIRTY_STAY_ON标志位
14 updateStayOnLocked(mDirty);
15 updateScreenBrightnessBoostLocked(mDirty);
16
17 // Phase 1: Update wakefulness.
18 // Loop because the wake lock and user activity computations are influenced
19 // by changes in wakefulness.
20 final long now = SystemClock.uptimeMillis();
21 int dirtyPhase2 = 0;
22 for (;;) {
23 int dirtyPhase1 = mDirty;
24 dirtyPhase2 |= dirtyPhase1;
25 mDirty = 0;
26
27 updateWakeLockSummaryLocked(dirtyPhase1);
28 updateUserActivitySummaryLocked(now, dirtyPhase1);
29 if (!updateWakefulnessLocked(dirtyPhase1)) {
30 break;
31 }
32 }
33
34 // Phase 2: Update display power state.
35 boolean displayBecameReady = updateDisplayPowerStateLocked(dirtyPhase2);
36
37 // Phase 3: Update dream state (depends on display ready signal).
38 updateDreamLocked(dirtyPhase2, displayBecameReady);
39
40 // Phase 4: Send notifications, if needed.
41 finishWakefulnessChangeIfNeededLocked();
42
43 // Phase 5: Update suspend blocker.
44 // Because we might release the last suspend blocker here, we need to make sure
45 // we finished everything else first!
46 updateSuspendBlockerLocked();
47 } finally {
48 Trace.traceEnd(Trace.TRACE_TAG_POWER);
49 }
50 }
这里还是需要把代码贴出来比较好，可以直观看到updatePowerStateLocked()有6个阶段
第0阶段：基本状态更新：
2.6.1、updateIsPoweredLocked()
1 private void updateIsPoweredLocked(int dirty) {
2 if ((dirty & DIRTY_BATTERY_STATE) != 0) {
3 final boolean wasPowered = mIsPowered;
4 final int oldPlugType = mPlugType;
5 final boolean oldLevelLow = mBatteryLevelLow;
6 //获取充电标志位、充电器类型、电量百分比、低电量标志位
7 mIsPowered = mBatteryManagerInternal.isPowered(BatteryManager.BATTERY_PLUGGED_ANY);
8 mPlugType = mBatteryManagerInternal.getPlugType();
9 mBatteryLevel = mBatteryManagerInternal.getBatteryLevel();
10 mBatteryLevelLow = mBatteryManagerInternal.getBatteryLevelLow();
11
12 if (DEBUG_SPEW) {
13 Slog.d(TAG, "updateIsPoweredLocked: wasPowered=" + wasPowered
14 + ", mIsPowered=" + mIsPowered
15 + ", oldPlugType=" + oldPlugType
16 + ", mPlugType=" + mPlugType
17 + ", mBatteryLevel=" + mBatteryLevel);
18 }
19 //充电器插拔时间发生、或者充电器类型更变则设置DIRTY_IS_POWERED标志位
20 if (wasPowered != mIsPowered || oldPlugType != mPlugType) {
21 mDirty |= DIRTY_IS_POWERED;
22
23 // Update wireless dock detection state.
24 //判断是否进行无线充电
25 final boolean dockedOnWirelessCharger = mWirelessChargerDetector.update(
26 mIsPowered, mPlugType, mBatteryLevel);
27
28 // Treat plugging and unplugging the devices as a user activity.
29 // Users find it disconcerting when they plug or unplug the device
30 // and it shuts off right away.
31 // Some devices also wake the device when plugged or unplugged because
32 // they don't have a charging LED.
33 //上面的注释意思是说插拔充电器可以看做是用户行为，当插拔充电器时如果设备没有给出提示则用户会比较疑惑
34 //特别是在设备没有充电指示灯的时，所以一般插拔充电器时会唤醒设备
35 final long now = SystemClock.uptimeMillis();
36 if (shouldWakeUpWhenPluggedOrUnpluggedLocked(wasPowered, oldPlugType,
37 dockedOnWirelessCharger)) {
38 //如果设置了插拔充电器时候需要唤醒设备，则在这里唤醒设备
39 wakeUpNoUpdateLocked(now, "android.server.power:POWER", Process.SYSTEM_UID,
40 mContext.getOpPackageName(), Process.SYSTEM_UID);
41 }
42 userActivityNoUpdateLocked(
43 now, PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, Process.SYSTEM_UID);
44
45 // Tell the notifier whether wireless charging has started so that
46 // it can provide feedback to the user.
47 //当无线充电器开始充电时给出提示音，在mNotifier中进行处理，播放一个ogg音频文件，我的三星设备是在/system/media/audio/ui/WirelessChargingStarted.ogg
48 //该路径下有不少ogg文件，有兴趣的可以看看都是在什么情况下播的
49 if (dockedOnWirelessCharger) {
50 mNotifier.onWirelessChargingStarted();
51 }
52 }
53 //如果电源插拔时间发生、或者是低电量标志位发生变化
54 if (wasPowered != mIsPowered || oldLevelLow != mBatteryLevelLow) {
55 if (oldLevelLow != mBatteryLevelLow && !mBatteryLevelLow) {
56 //当设备从低电量切换为非低电量，则设置自动打盹标志为false（因为已经不是低电量了）
57 if (DEBUG_SPEW) {
58 Slog.d(TAG, "updateIsPoweredLocked: resetting low power snooze");
59 }
60 mAutoLowPowerModeSnoozing = false;
61 }
62 //发送广播ACTION_POWER_SAVE_MODE_CHANGED，该广播在系统多处进行处理，在SystemUI中进行处理，如果低电量则给出提示
63 updateLowPowerModeLocked();
64 }
65 }
66 }
2.6.2、updateScreenBrightnessBoostLocked()
1 private void updateScreenBrightnessBoostLocked(int dirty) {
2 if ((dirty & DIRTY_SCREEN_BRIGHTNESS_BOOST) != 0) {
3 if (mScreenBrightnessBoostInProgress) {
4 final long now = SystemClock.uptimeMillis();
5 //删除屏幕亮度提升超时广播
6 mHandler.removeMessages(MSG_SCREEN_BRIGHTNESS_BOOST_TIMEOUT);
7 if (mLastScreenBrightnessBoostTime > mLastSleepTime) {
8 final long boostTimeout = mLastScreenBrightnessBoostTime +
9 SCREEN_BRIGHTNESS_BOOST_TIMEOUT;
10 //如果超时还没有发生，则重新发送广播（定时广播)
11 if (boostTimeout > now) {
12 Message msg = mHandler.obtainMessage(MSG_SCREEN_BRIGHTNESS_BOOST_TIMEOUT);
13 msg.setAsynchronous(true);
14 mHandler.sendMessageAtTime(msg, boostTimeout);
15 return;
16 }
17 }
18 //运行到这里有2个条件
19 //mLastScreenBrightnessBoostTime <= mLastSleepTime 说明还在睡眠中
20 //boostTimeout <= now 说明屏幕提升超时发生
21 mScreenBrightnessBoostInProgress = false;
22 mNotifier.onScreenBrightnessBoostChanged();
23 userActivityNoUpdateLocked(now,
24 PowerManager.USER_ACTIVITY_EVENT_OTHER, 0, Process.SYSTEM_UID);
25 }
26 }
27 }
第1阶段：基本状态更新：
2.6.3、updateWakeLockSummaryLocked()
1 @SuppressWarnings("deprecation")
2 private void updateWakeLockSummaryLocked(int dirty) {
3 if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_WAKEFULNESS)) != 0) {
4 mWakeLockSummary = 0;
5 //mWakeLocks保存了用户创建的所有wakelock
6 final int numWakeLocks = mWakeLocks.size();
7 for (int i = 0; i < numWakeLocks; i++) {
8 final WakeLock wakeLock = mWakeLocks.get(i);
9 switch (wakeLock.mFlags & PowerManager.WAKE_LOCK_LEVEL_MASK) {
10 case PowerManager.PARTIAL_WAKE_LOCK:
11 if (!wakeLock.mDisabled) {
12 // We only respect this if the wake lock is not disabled.
13 if(!wakeLock.mPackageName.equals("com.google.android.gms")){
14 mWakeLockSummary |= WAKE_LOCK_CPU;
15 }
16 }
17 break;
18 case PowerManager.FULL_WAKE_LOCK:
19 mWakeLockSummary |= WAKE_LOCK_SCREEN_BRIGHT | WAKE_LOCK_BUTTON_BRIGHT;
20 break;
21 case PowerManager.SCREEN_BRIGHT_WAKE_LOCK:
22 mWakeLockSummary |= WAKE_LOCK_SCREEN_BRIGHT;
23 break;
24 case PowerManager.SCREEN_DIM_WAKE_LOCK:
25 mWakeLockSummary |= WAKE_LOCK_SCREEN_DIM;
26 break;
27 case PowerManager.PROXIMITY_SCREEN_OFF_WAKE_LOCK:
28 mWakeLockSummary |= WAKE_LOCK_PROXIMITY_SCREEN_OFF;
29 break;
30 case PowerManager.DOZE_WAKE_LOCK:
31 mWakeLockSummary |= WAKE_LOCK_DOZE;
32 break;
33 case PowerManager.DRAW_WAKE_LOCK:
34 mWakeLockSummary |= WAKE_LOCK_DRAW;
35 break;
36 }
37 }
38 /**
39 根据mWakefullness的状态取消某些锁的作用，意思就是说在系统处于特定状态时，有些锁是没有意义的，需要取消mWakeLockSummary中相应的标志位
40 */
41 // Cancel wake locks that make no sense based on the current state.
42 if (mWakefulness != WAKEFULNESS_DOZING) {
43 mWakeLockSummary &= ~(WAKE_LOCK_DOZE | WAKE_LOCK_DRAW);
44 }
45 /**
46 注意这里，当mWakefulless状态为asleep时，WAKE_LOCK_SCREEN_BRIGHT、WAKE_LOCK_SCREEN_DIM、WAKE_LOCK_BUTTON_BRIGHT、WAKE_LOCK_PROXIMITY_SCREEN_OFF
47 这几种WakeLock的标志位都会被清空，标志位被清空作用就是类似系统释放了这些锁；仔细看唯独WAKE_LOCK_CPU标志位不变，说明PARTIAL_WAKE_LOCK在系统休眠的
48 时候是不是会自动清空的，如果系统中存在PARTIAL_WAKE_LOCK，那么除非手动释放，不然系统将没办法进入休眠
49 如果第三方的应用获取了PARTIAL_WAKE_LOCK，但是在系统休眠时又不是释放该怎么办呢?在后面调试经验中会给出答案。
50 */
51 if (mWakefulness == WAKEFULNESS_ASLEEP
52 || (mWakeLockSummary & WAKE_LOCK_DOZE) != 0) {
53 mWakeLockSummary &= ~(WAKE_LOCK_SCREEN_BRIGHT | WAKE_LOCK_SCREEN_DIM
54 | WAKE_LOCK_BUTTON_BRIGHT);
55 if (mWakefulness == WAKEFULNESS_ASLEEP) {
56 mWakeLockSummary &= ~WAKE_LOCK_PROXIMITY_SCREEN_OFF;
57 }
58 }
59 /**
60 根据mWakefullness的状态增加某些锁的作用，就是说当系统处于特定状态时，需要某些锁来保持系统的状态，比如WAKEFULNESS_AWAKE状态肯定是要保持CPU运行的，所以
61 需要添加WAKE_LOCK_CPU标志位以确保cpu处于运行状态
62 */
63 // Infer implied wake locks where necessary based on the current state.
64 if ((mWakeLockSummary & (WAKE_LOCK_SCREEN_BRIGHT | WAKE_LOCK_SCREEN_DIM)) != 0) {
65 if (mWakefulness == WAKEFULNESS_AWAKE) {
66 mWakeLockSummary |= WAKE_LOCK_CPU | WAKE_LOCK_STAY_AWAKE;
67 } else if (mWakefulness == WAKEFULNESS_DREAMING) {
68 mWakeLockSummary |= WAKE_LOCK_CPU;
69 }
70 }
71 if ((mWakeLockSummary & WAKE_LOCK_DRAW) != 0) {
72 mWakeLockSummary |= WAKE_LOCK_CPU;
73 }
74
75 if (DEBUG_SPEW) {
76 Slog.d(TAG, "updateWakeLockSummaryLocked: mWakefulness="
77 + PowerManagerInternal.wakefulnessToString(mWakefulness)
78 + ", mWakeLockSummary=0x" + Integer.toHexString(mWakeLockSummary));
79 }
80 }
81 }
2.6.4、updateUserActivitySummaryLocked()
这个方法只是更新mUserActivitySummary的值，内容比较简单，这里不再贴代码分析了，读者自行分析吧
2.6.5、updateWakefulnessLocked()
1 private boolean updateWakefulnessLocked(int dirty) {
2 boolean changed = false;
3 if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_USER_ACTIVITY | DIRTY_BOOT_COMPLETED
4 | DIRTY_WAKEFULNESS | DIRTY_STAY_ON | DIRTY_PROXIMITY_POSITIVE
5 | DIRTY_DOCK_STATE)) != 0) {
6 //注意这里会改变mWakefullness的值，但是mWakefullness的值会影响锁的有效性，因此阶段2的处理在一个for循环中
7 if (mWakefulness == WAKEFULNESS_AWAKE && isItBedTimeYetLocked()) {
8 if (DEBUG_SPEW) {
9 Slog.d(TAG, "updateWakefulnessLocked: Bed time...");
10 }
11 final long time = SystemClock.uptimeMillis();
12 if (shouldNapAtBedTimeLocked()) {
13 changed = napNoUpdateLocked(time, Process.SYSTEM_UID);
14 } else {
15 changed = goToSleepNoUpdateLocked(time,
16 PowerManager.GO_TO_SLEEP_REASON_TIMEOUT, 0, Process.SYSTEM_UID);
17 }
18 }
19 }
20 return changed;
21 }
第2、3、4、5代码比较简单，这里就不分析了，读者自行分析，下面我们来关注第6阶段
阶段6：
2.6.6、updateSuspendBlockerLocked()
1 private void updateSuspendBlockerLocked() {
2 final boolean needWakeLockSuspendBlocker = ((mWakeLockSummary & WAKE_LOCK_CPU) != 0);
3 final boolean needDisplaySuspendBlocker = needDisplaySuspendBlockerLocked();
4 final boolean autoSuspend = !needDisplaySuspendBlocker;
5 final boolean interactive = mDisplayPowerRequest.isBrightOrDim();
6
7 // Disable auto-suspend if needed.
8 // FIXME We should consider just leaving auto-suspend enabled forever since
9 // we already hold the necessary wakelocks.
10 if (!autoSuspend && mDecoupleHalAutoSuspendModeFromDisplayConfig) {
11 setHalAutoSuspendModeLocked(false);
12 }
13 /**
14 从上面我们知道有WAKE_LOCK_CPU标志的话就获取一个suspendblocker，这才是正真会阻止cpu待机的东西
15 */
16 // First acquire suspend blockers if needed.
17 if (needWakeLockSuspendBlocker && !mHoldingWakeLockSuspendBlocker) {
18 mWakeLockSuspendBlocker.acquire();
19 mHoldingWakeLockSuspendBlocker = true;
20 }
21 /*
22 只有屏幕亮的时候才需要display suspendblocker，当屏幕灭或者doz的时候这里不会获取suspendblocker
23 */
24 if (needDisplaySuspendBlocker && !mHoldingDisplaySuspendBlocker) {
25 mDisplaySuspendBlocker.acquire();
26 mHoldingDisplaySuspendBlocker = true;
27 }
28
29 /*
30 设置设备为可交互模式
31 */
32 // Inform the power HAL about interactive mode.
33 // Although we could set interactive strictly based on the wakefulness
34 // as reported by isInteractive(), it is actually more desirable to track
35 // the display policy state instead so that the interactive state observed
36 // by the HAL more accurately tracks transitions between AWAKE and DOZING.
37 // Refer to getDesiredScreenPolicyLocked() for details.
38 if (mDecoupleHalInteractiveModeFromDisplayConfig) {
39 // When becoming non-interactive, we want to defer sending this signal
40 // until the display is actually ready so that all transitions have
41 // completed. This is probably a good sign that things have gotten
42 // too tangled over here...
43 if (interactive || mDisplayReady) {
44 setHalInteractiveModeLocked(interactive);
45 }
46 }
47 /*
48 注意这里needWakeLockSuspendBlocker为ture的话是不会释放mWakeLockSuspendBlocker的，所以系统会无法待机
49 这样就能解释的通为什么PARTIAL_WAKE_LOCK级别的锁会导致不能待机了:
50 app-->newWakeLock(PowerManager.PARTIAL_WAKE_LOCK,flag) --->PMS设置mWakeLockSummary的WAKE_LOCK_CPU标志位
51 --->PMS 因为WAKE_LOCK_CPU标志位存在mWakeLockSuspendBlocker.acquire()-->待机失败
52 */
53 // Then release suspend blockers if needed.
54 if (!needWakeLockSuspendBlocker && mHoldingWakeLockSuspendBlocker) {
55 mWakeLockSuspendBlocker.release();
56 mHoldingWakeLockSuspendBlocker = false;
57 }
58 if (!needDisplaySuspendBlocker && mHoldingDisplaySuspendBlocker) {
59 mDisplaySuspendBlocker.release();
60 mHoldingDisplaySuspendBlocker = false;
61 }
62
63 //如果条件成立的话设置自动待机模式
64 // Enable auto-suspend if needed.
65 if (autoSuspend && mDecoupleHalAutoSuspendModeFromDisplayConfig) {
66 setHalAutoSuspendModeLocked(true);
67 }
68 }
三、PowerManager用法
PowerManager的用法很简单，我们主要看下PowerManager创建锁这部分：
newWakeLock(int levelAndFlags, String tag)
levelAndFlags： 就是上边表格中的几个flag，可以看到不同的flag对系统的影响并不一样
PARTIAL_WAKE_LOCK： 保持cpu运转状态，屏幕键盘灭，按power键该锁不会被系统自动释放，所以系统无法进去待机休眠
SCREEN_DIM_WAKE_LOCK： 保持cpu处于运行状态，屏幕微亮、键盘灭，但是按power键进入待机休眠时会自动释放
SCREEN_BRIGHT_WAKE_LOCK： 保持cpu处于运行状态，屏幕亮、键盘灭，但是按power键进入待机休眠时会自动释放
FULL_WAKE_LOCK： 保持cpu处于运行状态，屏幕、键盘亮，但是按power键进入待机休眠时会自动释放
注意：官方的文档介绍尽量不要使用WAKE_LOCK，用FLAG_KEEP_SCREEN_ON标志位代替WAKE_LOCK，用如下方式：
1 getWindow().addFlags(WindowManager.LayoutParams.FLAG_KEEP_SCREEN_ON);
当然该方法只是针对当前Activity，如果要整个应用都保持屏幕亮，则可以写了BaseActivity并设置该标志位，其他Activity继承BaseActivity即可。
四、PowerManagerService调试
PMS中最容易出现的问题就是待机待不下去，原因就是上面说的PARTIAL_WAKE_LOCK级别的锁没有释放，按道理说这种锁的释放应该由应用自身来作的，但是一些第三方的应用（Google的一些应用就很多这种锁）没有释放的话该怎么办呢？
下面介绍两种办法：
1、强制不给设置WAKE_LOCK_CPU标志位
1 private void updateWakeLockSummaryLocked(int dirty) {
2 if ((dirty & (DIRTY_WAKE_LOCKS | DIRTY_WAKEFULNESS)) != 0) {
3 mWakeLockSummary = 0;
4 //mWakeLocks保存了用户创建的所有wakelock
5 final int numWakeLocks = mWakeLocks.size();
6 for (int i = 0; i < numWakeLocks; i++) {
7 final WakeLock wakeLock = mWakeLocks.get(i);
8 switch (wakeLock.mFlags & PowerManager.WAKE_LOCK_LEVEL_MASK) {
9 case PowerManager.PARTIAL_WAKE_LOCK:
10 if (!wakeLock.mDisabled) {
11 // We only respect this if the wake lock is not disabled.
12 //com.google.android.gms获取了PARTIAL_WAKE_LOCK，但是不给设置WAKE_LOCK_CPU标志位
13 if(!wakeLock.mPackageName.equals("com.google.android.gms")){
14 mWakeLockSummary |= WAKE_LOCK_CPU;
15 }else{
16 mWakeLockSummary |= WAKE_LOCK_SCREEN_BRIGHT;
17 }
18 }
2、让系统自动清楚WAKE_LOCK_CPU标志
1 if (mWakefulness == WAKEFULNESS_ASLEEP
2 || (mWakeLockSummary & WAKE_LOCK_DOZE) != 0) {
3 mWakeLockSummary &= ~(WAKE_LOCK_SCREEN_BRIGHT | WAKE_LOCK_SCREEN_DIM
4 | WAKE_LOCK_BUTTON_BRIGHT |WAKE_LOCK_CPU); //待机休眠时清楚 WAKE_LOCK_CPU
5 if (mWakefulness == WAKEFULNESS_ASLEEP) {
6 mWakeLockSummary &= ~WAKE_LOCK_PROXIMITY_SCREEN_OFF;
7 }
8 }
dumpsysy power可打印PMS中锁信息：
五、总结
总的来说PMS的流程并不复杂，不过需要静下心来分析代码仍然不是一件很容易的事情，本人水平有限，有不足之处请指出，后续我会持续更新修改。
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