android 关机流程分析

嵌入式系统一般都有一个关机按键，长按这个按键系统会弹出关机对话框，提示关机确认，

关机动作从按键触发中断，linux kernel层给android framework层返回按键事件进入 framework层，再从framework层到kernel层执行kernel层关机任务。

长按键对应的handler代码：

frameworks/policies/base/phone/com/android/internal/policy/impl/PhoneWindowManager.java
Runnable mPowerLongPress;

private final Runnable mPowerLongPress = new Runnable() {
public void run() {
if (!mPowerKeyHandled) {
mPowerKeyHandled = true;
performHapticFeedbackLw(null, HapticFeedbackConstants.LONG_PRESS, false);
sendCloseSystemWindows(SYSTEM_DIALOG_REASON_GLOBAL_ACTIONS);
showGlobalActionsDialog();
}
}
};

mPowerLongPress 启动关机对话框

(frameworks/policies/base/phone/com/android/internal/policy/impl/GlobalActions.java)

如果我们选择Power OFF’,会调用ShutdownThread.shutdown. 启动关机线程执行关机动作。

frameworks/base/core/java/com/android/internal/app/ShutdownThread.java

真正关机流程：

(1)广播全局事件，ACTION_SHUTDOWN Intent

(2)shutdown ActivityManager 服务

(3) 停止蓝牙服务

(4) 停止电话服务 (radio phone service)

(5)停止mount 服务

(6) 调用Power.shutdown() 进入native 层

frameworks/base/core/java/android/os/Power.java

power的native实现代码：

frameworks/base/core/jni/android_os_Power.cpp

static void android_os_Power_shutdown(JNIEnv *env, jobject clazz)
{
sync();
#ifdef HAVE_ANDROID_OS
reboot(RB_POWER_OFF);
#endif
}

sync, reboot 为linux系统调用，进入linux内核关机流程。

完毕。

1.通过logcat找到关机流程

frameworks/base/core/java/com/android/internal/app/ShutdownThread.java

public void run() {
boolean bluetoothOff;
boolean radioOff;

BroadcastReceiver br = new BroadcastReceiver() {
@Override public void onReceive(Context context, Intent intent) {
// We don't allow apps to cancel this, so ignore the result.
broadcastDone();
}
};

Log.i(TAG, "Sending shutdown broadcast...");

// First send the high-level shut down broadcast.
mBroadcastDone = false;
mContext.sendOrderedBroadcast(new Intent(Intent.ACTION_SHUTDOWN), null,
br, mHandler, 0, null, null);

final long endTime = System.currentTimeMillis() + MAX_BROADCAST_TIME;
synchronized (mBroadcastDoneSync) {
while (!mBroadcastDone) {
long delay = endTime - System.currentTimeMillis();
if (delay <= 0) {
Log.w(TAG, "Shutdown broadcast timed out");
break;
}
try {
mBroadcastDoneSync.wait(delay);
} catch (InterruptedException e) {
}
}
}

Log.i(TAG, "Shutting down activity manager...");

final IActivityManager am =
ActivityManagerNative.asInterface(ServiceManager.checkService("activity"));
if (am != null) {
try {
am.shutdown(MAX_BROADCAST_TIME);
} catch (RemoteException e) {
}
}

final ITelephony phone =
ITelephony.Stub.asInterface(ServiceManager.checkService("phone"));
final IBluetooth bluetooth =
IBluetooth.Stub.asInterface(ServiceManager.checkService(
BluetoothAdapter.BLUETOOTH_SERVICE));

final IMountService mount =
IMountService.Stub.asInterface(
ServiceManager.checkService("mount"));

try {
bluetoothOff = bluetooth == null ||
bluetooth.getBluetoothState() == BluetoothAdapter.STATE_OFF;
if (!bluetoothOff) {
Log.w(TAG, "Disabling Bluetooth...");
bluetooth.disable(false); // disable but don't persist new state
}
} catch (RemoteException ex) {
Log.e(TAG, "RemoteException during bluetooth shutdown", ex);
bluetoothOff = true;
}

try {
radioOff = phone == null || !phone.isRadioOn();
if (!radioOff) {
Log.w(TAG, "Turning off radio...");
phone.setRadio(false);
}
} catch (RemoteException ex) {
Log.e(TAG, "RemoteException during radio shutdown", ex);
radioOff = true;
}

Log.i(TAG, "Waiting for Bluetooth and Radio...");

// Wait a max of 32 seconds for clean shutdown
for (int i = 0; i < MAX_NUM_PHONE_STATE_READS; i++) {
if (!bluetoothOff) {
try {
bluetoothOff =
bluetooth.getBluetoothState() == BluetoothAdapter.STATE_OFF;
} catch (RemoteException ex) {
Log.e(TAG, "RemoteException during bluetooth shutdown", ex);
bluetoothOff = true;
}
}
if (!radioOff) {
try {
radioOff = !phone.isRadioOn();
} catch (RemoteException ex) {
Log.e(TAG, "RemoteException during radio shutdown", ex);
radioOff = true;
}
}
if (radioOff && bluetoothOff) {
Log.i(TAG, "Radio and Bluetooth shutdown complete.");
break;
}
SystemClock.sleep(PHONE_STATE_POLL_SLEEP_MSEC);
}

// Shutdown MountService to ensure media is in a safe state
try {
if (mount != null) {
mount.shutdown();
} else {
Log.w(TAG, "MountService unavailable for shutdown");
}
} catch (Exception e) {
Log.e(TAG, "Exception during MountService shutdown", e);
}

//shutdown power
Log.i(TAG, "Performing low-level shutdown...");
Power.shutdown();
}

logcat显示到最后一步了，但是系统还没有关闭，是电源关闭有问题。

2. Power.shutdown();
找这个 android.os.Power 模块

frameworks/base/core/java/android/os/power.java 中有调用shutdown（）jni接口

3. jni接口

frameworks/base/core/jni/android_os_Power.cpp

static void android_os_Power_shutdown(JNIEnv *env, jobject clazz)
{
sync();
#ifdef HAVE_ANDROID_OS
reboot(RB_POWER_OFF);
#endif
}

其中，RB_POWER_OFF 及RB_AUTOBOOT （重启）定义bionic/libc/include/sys/reboot.h

#define RB_AUTOBOOT LINUX_REBOOT_CMD_RESTART

#define RB_HALT_SYSTEM LINUX_REBOOT_CMD_HALT

#define RB_POWER_OFF LINUX_REBOOT_CMD_POWER_OFF

系统最后会执行系统调用sys_reboot（reboot）。reboot通常定义在内核kernel/kernel/sys.c

4 。内核部分。 kernel/sys.c

其中，

if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
cmd = LINUX_REBOOT_CMD_HALT;

lock_kernel();
switch (cmd) {
case LINUX_REBOOT_CMD_RESTART:
kernel_restart(NULL);
break;

case LINUX_REBOOT_CMD_CAD_ON:
C_A_D = 1;
break;

case LINUX_REBOOT_CMD_CAD_OFF:
C_A_D = 0;
break;

case LINUX_REBOOT_CMD_HALT:
kernel_halt();
unlock_kernel();
do_exit(0);
break;

case LINUX_REBOOT_CMD_POWER_OFF:
printk("test powe down in %s(%d)\n", __FILE__, __LINE__);
kernel_power_off();
unlock_kernel();
do_exit(0);
break;

当pm_power_off为空时，由上层传入的命令LINUX_REBOOT_CMD_POWER_OFF会变为LINUX_REBOOT_CMD_HALT，从而执行 kernel_halt()函数。在该函数中，会执行函数machine_halt()。错误原因就在这儿（pm_power_off为空）。

函数指针pm_power_off是与平台相关的指针，

添加函数

static void lpc32xx_power_off(void)
{
__raw_writel((0x1<<9),GPIO_P2_OUTP_CLR(GPIO_IOBASE));
}

在ea3250_board_init中添加

pm_power_off = lpc32xx_power_off;

编译内核，OK

android层可以正常关闭电源了。。，

原文： http://blog.chinaunix.net/uid-24227137-id-3248111.html

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