and5.1PowerManagerService深入分析(二)PowerManager中各函数

and5.1PowerManagerService深入分析（二）PowerManager中各函数今天主要从PowerManager中的接口入手去分析PowerManagerService.先分析PowerManager中的一个内部类WakeLock，可以使用这个类持睡眠锁。

下面是PowerManager中WakeLock内部类来里面的代码：[java] view plain copypublic void acquire() {synchronized (mToken) {acquireLocked();}}/*** Acquires the wake lock with a timeout.* <p>* Ensures that the device is on at the level requested when* the wake lock was created. The lock will be released after the given timeout* expires.* </p>** @param timeout The timeout after which to release the wake lock, in milliseconds.*/public void acquire(long timeout) {synchronized (mToken) {acquireLocked();mHandler.postDelayed(mReleaser, timeout);//利用消息机制做一个timeout的持锁，mReleaser中是对该锁释放了}}private void acquireLocked() {if (!mRefCounted || mCount++ == 0) {// Do this even if the wake lock is already thought to be held (mHeld == true)// because non-reference counted wake locks are not always properly released.// For example, the keyguard's wake lock might be forcibly released by the// power manager without the keyguard knowing. A subsequent call to acquire// should immediately acquire the wake lock once again despite never having// been explicitly released by the keyguard.mHandler.removeCallbacks(mReleaser);Trace.asyncTraceBegin(Trace.TRACE_TAG_POWER, mTraceName, 0);try {mService.acquireWakeLock(mToken, mFlags, mTag, mPackageName,mWorkSource,//调用PMS的acquireWakeLockmHistoryTag);} catch (RemoteException e) {}mHeld = true;}}先看PMS里的acquireWakeLock函数，先做一些权限的检查，然后就调用acquireWakeLockInternal函数。

[java] view plain copy@Override // Binder callpublic void acquireWakeLock(IBinder lock, int flags, String tag, String packageName, WorkSource ws, String historyTag) {if (lock == null) {throw new IllegalArgumentException("lock must not be null");}if (packageName == null) {throw new IllegalArgumentException("packageName must not be null");}PowerManager.validateWakeLockParameters(flags, tag);mContext.enforceCallingOrSelfPermission(android.Manifest.permission.WAKE_LOCK, null);if ((flags & PowerManager.DOZE_W AKE_LOCK) != 0) {mContext.enforceCallingOrSelfPermission(android.Manifest.permission.DEVICE_POWER, null);}if (ws != null && ws.size() != 0) {mContext.enforceCallingOrSelfPermission(android.Manifest.permission.UPDATE_DEVICE_STATS, null);} else {ws = null;}final int uid = Binder.getCallingUid();final int pid = Binder.getCallingPid();final long ident = Binder.clearCallingIdentity();try {acquireWakeLockInternal(lock, flags, tag, packageName, ws, historyTag, uid, pid);} finally {Binder.restoreCallingIdentity(ident);}}acquireWakeLockInternal函数[java] view plain copyprivate void acquireWakeLockInternal(IBinder lock, int flags, String tag, String packageName, WorkSource ws, String historyTag, int uid, int pid) {synchronized (mLock) {if (DEBUG_SPEW) {Slog.d(TAG, "acquireWakeLockInternal: lock=" + Objects.hashCode(lock)+ ", flags=0x" + Integer.toHexString(flags)+ ", tag=\"" + tag + "\", ws=" + ws + ", uid=" + uid + ", pid=" + pid);}WakeLock wakeLock;int index = findWakeLockIndexLocked(lock);//查找这个IBinder的锁。

因为每个应用都是一个进程，通过binder通信与PMS交互。

IBinder是唯一的boolean notifyAcquire;if (index >= 0) {//找到wakeLock = mWakeLocks.get(index);if (!wakeLock.hasSameProperties(flags, tag, ws, uid, pid)) {//如果属性不一样就更新// Update existing wake lock. This shouldn't happen but is harmless.notifyWakeLockChangingLocked(wakeLock, flags, tag, packageName,//通知电池统计uid, pid, ws, historyTag);wakeLock.updateProperties(flags, tag, packageName, ws, historyTag, uid, pid);}notifyAcquire = false;} else {//没找到wakeLock = new WakeLock(lock, flags, tag, packageName, ws, historyTag, uid, pid);//新建一个WakeLock加入列表try {lock.linkToDeath(wakeLock, 0);} catch (RemoteException ex) {throw new IllegalArgumentException("Wake lock is already dead.");}mWakeLocks.add(wakeLock);notifyAcquire = true;}applyWakeLockFlagsOnAcquireLocked(wakeLock, uid);//下面详细分析mDirty |= DIRTY_WAKE_LOCKS;//mDirty 标志位置位updatePowerStateLocked();//更新power状态if (notifyAcquire) {// This needs to be done last so we are sure we have acquired the// kernel wake lock. Otherwise we have a race where the system may// go to sleep between the time we start the accounting in battery// stats and when we actually get around to telling the kernel to// stay awake.notifyWakeLockAcquiredLocked(wakeLock);//通知电池统计那块}}}findWakeLockIndexLocked函数[java] view plain copyprivate int findWakeLockIndexLocked(IBinder lock) {final int count = mWakeLocks.size();for (int i = 0; i < count; i++) {if (mWakeLocks.get(i).mLock == lock) {return i;}}return -1;}applyWakeLockFlagsOnAcquireLocked函数[java] view plain copyprivate void applyWakeLockFlagsOnAcquireLocked(WakeLock wakeLock, int uid) { if ((wakeLock.mFlags & PowerManager.ACQUIRE_CAUSES_WAKEUP) != 0//如果持的锁有ACQUIRE_CAUSES_WAKEUP，还有屏幕锁的话，会wakeup设备&& isScreenLock(wakeLock)) {wakeUpNoUpdateLocked(SystemClock.uptimeMillis(), uid);}}[java] view plain copy@SuppressWarnings("deprecation")private static boolean isScreenLock(final WakeLock wakeLock) {switch (wakeLock.mFlags & PowerManager.W AKE_LOCK_LEVEL_MASK) { case PowerManager.FULL_WAKE_LOCK:case PowerManager.SCREEN_BRIGHT_W AKE_LOCK:case PowerManager.SCREEN_DIM_WAKE_LOCK:return true;}return false;}updatePowerStateLocked这个函数是所有的地方都会调用，因此我们最后分析。