android 关机 流程分析

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

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）。

5.

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。。，