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

and5.1PowerManagerService

深入分析

（二）

PowerManager

中各函数< /p>

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< /p>

中

WakeLock

内部类来里面的代码 ：

[java] view plain copy

public void acquire() {

synchronized (mToken) {

acquireLocked();

}

}

/**

* Acquires the wake lock with a timeout.

*

* 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.

*

*

* @param timeout The timeout after which to release the wake lock, in milliseconds.

*/

public void acquire(long timeout) {

synchronized (mToken) {

acquireLocked();

layed(mReleaser, timeout);//

利用消息机制做一个

timeout

的持锁，

< br>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.

Callbacks(mReleaser);

raceBegin(_TAG_POWER, mTraceName, 0);

try {

eWakeLock(mToken,

mFlags,

mTag,

mPackageName,

< br>mWorkSource,//

调用

PMS

的

acquireWakeLock

mHistoryTag);

} catch (RemoteException e) {

}

mHeld = true;

}

}

先

看

PMS

里

的

acq uireWakeLock

函

数

，

先

做

一

些

权

限

的

检

查

，

然

后

< br>就

调

用

acquireWake LockInternal

函数。

[java] view plain copy

@Override // Binder call

public void acquireWakeLock(IBinder lock, int flags, String tag, String packageName,

WorkSource ws, String historyTag) {

if (lock == null) {

throw new IllegalArgumentException(

}

if (packageName == null) {

throw new IllegalArgumentException(

}

teWakeLockParameters(flags, tag);

eCallingOrSelfPermission(_LOCK,

null);

if ((flags & _W

AKE_LOCK) != 0) {

eCallingOrSelfPermission(

_POWER, null);

}

if (ws != null && () != 0) {

eCallingOrSelfPermission(

_DEVICE_STATS, null);

} else {

ws = null;

}

final int uid = lingUid();

final int pid = lingPid();

final long ident = allingIdentity();

try {

acquireWakeLockInternal(lock, flags, tag, packageName, ws, historyTag, uid, pid);

} finally {

eCallingIdentity(ident);

}

}

ac quireWakeLockInternal

函数

[java] view plain copy

private 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

,

+

+

}

WakeLock wakeLock;

int index = fin dWakeLockIndexLocked(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 = (index);

if

(!eProperties(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);

Properties(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 {

Death(wakeLock, 0);

} catch (RemoteException ex) {

throw new IllegalArgumentException(

}

(wakeLock);

notifyAcquire = true;

}

app lyWakeLockFlagsOnAcquireLocked(wakeLock, uid);//

下面详细分析

mDirty |= DIRTY_WAKE_LOCKS;//mDirty

标志位置位

updatePowerStateLocked();//

更新

power

状态

< br>

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.

notifyWakeLockAcquiredLocke d(wakeLock);//

通知电池统计那块

}

}

}

fi ndWakeLockIndexLocked

函数

[java] view plain copy

private int findWakeLockIndexLocked(IBinder lock) {

final int count = ();

for (int i = 0; i < count; i++) {

if ((i).mLock == lock) {

return i;

}

}

return -1;

}

ap plyWakeLockFlagsOnAcquireLocked

函数

[java] view plain copy

private void applyWakeLockFlagsOnAcquireLocked(WakeLock wakeLock, int uid) {

if

((

&

E_CAUSES_WAKEUP)

!=

< br>0//

如果持的

锁有

ACQUI RE_CAUSES_WAKEUP

，还有屏幕锁的话，会

wa keup

设备

&& isScreenLock(wakeLock)) {

wakeUpNoUpdateLocked(Millis(), uid);

}

}

[java] view plain copy

@SuppressWarnings(

private static boolean isScreenLock(final WakeLock wakeLock) {

switch ( & PowerManager.W

AKE_LOCK_LEVEL_MASK) {

case _WAKE_LOCK:

case _BRIGHT_W

AKE_LOCK:

case _DIM_WAKE_LOCK:

return true;

}

return false;

}

up datePowerStateLocked

这个函数是所有的地方都会调用，因此我们 最后分析。

下面看下释放锁，

releaseWakeLockInternal

函数：