Android关机流程

转自：http://www.2cto.com/kf/201501/367859.html

ShutdownThread.java文件

stop playing music，因为后面可能要playing shutdown music.

代码如下：

 

 

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private static void beginShutdownSequence(Context context) {

  ....

        //acquire audio focus to make the other apps to stop playing muisc

        mAudioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);

        mAudioManager.requestAudioFocus(null,

                AudioManager.STREAM_MUSIC, AudioManager.AUDIOFOCUS_GAIN);

 

show system dialog to indicate phone is shutting down，如果没有关机动画的话，要show一个关机提示出来。

代码如下：

 

 

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if (!checkAnimationFileExist()) {

    // throw up an indeterminate system dialog to indicate radio is

    // shutting down.

    ProgressDialog pd =new ProgressDialog(context);

    pd.setTitle(context.getText(com.android.internal.R.string.power_off));

    pd.setMessage(context.getText(com.android.internal.R.string.shutdown_progress));

    pd.setIndeterminate(true);

    pd.setCancelable(false);

    pd.getWindow().setType(WindowManager.LayoutParams.TYPE_KEYGUARD_DIALOG);

 

    pd.show();

}

Hold the wakelock,make sure we never fall asleep again，抓锁防止机器关机过程中休眠

 

代码如下：

 

 

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sInstance.mCpuWakeLock = sInstance.mPowerManager.newWakeLock(

        PowerManager.PARTIAL_WAKE_LOCK, TAG + -cpu);//这个只是锁住cpu不进入休眠，但screen是off的，需full锁来保证screen常亮

sInstance.mCpuWakeLock.setReferenceCounted(false);

sInstance.mCpuWakeLock.acquire();

 

make sure the screen stays on,再抓一个full锁，防止屏幕半暗

代码如下：

 

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sInstance.mScreenWakeLock = sInstance.mPowerManager.newWakeLock(

        PowerManager.FULL_WAKE_LOCK, TAG + -screen);//保持srceen常亮

sInstance.mScreenWakeLock.setReferenceCounted(false);

sInstance.mScreenWakeLock.acquire();

起一下新进程

 

sending shutdown broadcast，发出广播，通知各app该保存数据赶紧的，我要关机了

代码如下：

 

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Intent intent = new Intent(Intent.ACTION_SHUTDOWN);

intent.addFlags(Intent.FLAG_RECEIVER_FOREGROUND);

mContext.sendOrderedBroadcastAsUser(intent,//发广播

        UserHandle.ALL,null, br, mHandler,0, null,null);

shutdown activity manager，关闭activity manager，即关闭AppOpsService，UsageStatsService，BatteryStatsService

 

注意：android L 与KK在关闭UsageStatsService上有所区别

代码如下：

[ActivityManagerService.java]

 

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final IActivityManager am =

            ActivityManagerNative.asInterface(ServiceManager.checkService(activity));

        if(am != null) {

            try{

                am.shutdown(MAX_BROADCAST_TIME);

            }catch (RemoteException e) {

            }

        }

shutdown package manager，保存app使用时间到 disk里，这是android L新增的功能。

 

代码如下：

[PackageManagerService.java]

 

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final PackageManagerService pm = (PackageManagerService)

    ServiceManager.getService(package);

if (pm != null) {

    pm.shutdown();

}

show shutdown animation，播放关机动画了

 

代码如下：

 

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private static void showShutdownAnimation() {

    /*

     * When boot completed, service.bootanim.exit property is set to 1.

     * Bootanimation checks this property to stop showing the boot animation.

     * Since we use the same code for shutdown animation, we

     * need to reset this property to 0. If this is not set to 0 then shutdown

     * will stop and exit after displaying the first frame of the animation

     */

    SystemProperties.set(service.bootanim.exit,0);

 

    SystemProperties.set(ctl.start, bootanim);//也是用bootanim进程，跟开关动画一样的方式。

}

shutdown radio[NFC,BT,MODEM],注意这里关闭modem这块与andorid KK的不一样。

 

代码如下：

shutdownRadios(MAX_RADIO_WAIT_TIME);

shutdown MountService,特别这里会导致关机失败。

代码如下：

 

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// Set initial variables and time out time.

mActionDone = false;

final long endShutTime = SystemClock.elapsedRealtime() + MAX_SHUTDOWN_WAIT_TIME;

synchronized(mActionDoneSync) {

    try{

        finalIMountService mount = IMountService.Stub.asInterface(

                ServiceManager.checkService(mount));

        if(mount != null) {

            mount.shutdown(observer);

        }else {

            Log.w(TAG, MountService unavailablefor shutdown);

        }

    }catch (Exception e) {

        Log.e(TAG, Exception during MountService shutdown, e);

    }

    while(!mActionDone) {

        longdelay = endShutTime - SystemClock.elapsedRealtime();

        if(delay <= 0) {

            Log.w(TAG, Shutdown wait timed out);

            break;

        }

        try{

            mActionDoneSync.wait(delay);

        }catch (InterruptedException e) {

        }

    }

}

走完上层关机流程，下面就要执行关机动作了。

 

代码如下：

 

 

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public static void rebootOrShutdown(booleanreboot, String reason) {

    deviceRebootOrShutdown(reboot, reason);

    if(reboot) {

        Log.i(TAG, Rebooting, reason:  + reason);

        PowerManagerService.lowLevelReboot(reason);//重启

        Log.e(TAG, Reboot failed, will attempt shutdown instead);

    }else if(SHUTDOWN_VIBRATE_MS > 0) {

        // vibrate before shutting down

        Vibrator vibrator =new SystemVibrator();

        try{

            vibrator.vibrate(SHUTDOWN_VIBRATE_MS, VIBRATION_ATTRIBUTES);

        }catch (Exception e) {

            // Failure to vibrate shouldn't interrupt shutdown.  Just log it.

            Log.w(TAG, Failed to vibrate during shutdown., e);

        }

 

        // vibrator is asynchronous so we need to wait to avoid shutting down too soon.

        try{

            Thread.sleep(SHUTDOWN_VIBRATE_MS);

        }catch (InterruptedException unused) {

        }

    }

 

    // Shutdown power

    Log.i(TAG, Performing low-level shutdown...);

    PowerManagerService.lowLevelShutdown();//关机

}

从代码上看始终会走到lowLevelShutdown()，但如果是重启就不会，lowLevelReboot()就停止了。

 

 

lowLevelShutdown()与lowLevelReboot()都在PowerManagerService.java实现，其实都只是设置一个属性：SystemProperties.set(sys.powerctl, xxx);

正是这个动作触发关机流程往下走，这涉及到init进程的4大功能，请参考我的另一篇文章Android的init进程

 

sys.powerctl属性触发开关在init.rc定义

 

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on property:sys.powerctl=*

    powerctl ${sys.powerctl}

我们来解读这句话，on property:sys.powerctl=*表示当属性sys.powerctl设置为任何值是都会跑到这里，触发动作是powerctl ${sys.powerctl},这个动作的意思是调用powerctl指令，并把sys.powerctl的值传给它。powerctl指令在init进程会执行。

 

从下面的表可知，powerctl对应的操作是do_powerctl

[system/core/init/keywords.h]

 

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KEYWORD(powerctl,    COMMAND,1, do_powerctl)

do_powerctl的实现

 

代码如下：

[system/core/init/builtins.c]

 

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int do_powerctl(int nargs, char **args)

{

....

 

    returnandroid_reboot(cmd, 0, reboot_target);

}

它调用android_reboot()函数，实现如下：

 

 

[system/core/libcutils/android_reboot.c]

 

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int android_reboot(int cmd, int flags UNUSED,char *arg)

{

    intret;

 

    sync();

    remount_ro();

 

    switch(cmd) {

        caseANDROID_RB_RESTART:

            ret = reboot(RB_AUTOBOOT);

            break;

 

        caseANDROID_RB_POWEROFF:

            ret = reboot(RB_POWER_OFF);

            break;

 

        caseANDROID_RB_RESTART2:

            ret = syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,

                           LINUX_REBOOT_CMD_RESTART2, arg);

            break;

 

        default:

            ret = -1;

    }

 

    returnret;

}

从这里看出它的主要工作：

 

sync() 回写block设备的内容，这是阻塞型操作。

remount_ro() 把block设备remount成ro，这里有个关键LOG：SysRq : Emergency Remount R/O，这是在logkit所能看到的最后一句LOG，因为remount成ro了，后面的LOG要通过last kmsg技术导出来。

reboot()或者syscall(__NR_reboot....，这点与android KK不同，这边直接用syscall功能，KK则通过汇编。

后面syscall(__NR_reboot...知道，直接调用了linux的__NR_reboot系统调用，这个系统调用会跑哪里？后面会讲。

reboot()这个函数实现如下：

[bionic/libc/bionic/reboot.cpp]

 

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int reboot(int mode) {

  return__reboot(LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2, mode, NULL);

}

调用了__reboot,它在汇编实现　如下：

 

[bionic/libc/arch-arm/syscalls/__reboot.S]

 

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ENTRY(__reboot)

    mov     ip, r7

    ldr     r7, =__NR_reboot//也跑到__NR_reboot系统调用

    swi     #0

    mov     r7, ip

    cmn     r0, #(MAX_ERRNO +1)

    bxls    lr

    neg     r0, r0

    b       __set_errno_internal

END(__reboot)

 

 

__NR_reboot对应的内核入口在哪里？

如下：

[bionic/libc/kernel/uapi/asm-generic/unistd.h]

 

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#define __NR_reboot142

它在内核入口如下：

 

注：bionic/libc/kernel/uapi/asm-generic/unistd.h与kernel/include/uapi/asm-generic/unistd.h是对应的，方便以后代码追踪

[kernel/include/uapi/asm-generic/unistd.h]

 

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#define __NR_reboot142

__SYSCALL(__NR_reboot, sys_reboot)

 

 

__NR_reboot 映射到 sys_reboot

grep 下sys_reboot　找不到，其实在这里

用SYSCALL_DEFINE定义

[kernel/kernel/sys.c]

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SYSCALL_DEFINE4(reboot,int, magic1, int, magic2, unsigned int, cmd,

        void__user *, arg)

{

    struct pid_namespace *pid_ns = task_active_pid_ns(current);

    charbuffer[256];

    intret = 0;

 

    /* We only trust the superuser with rebooting the system. */

    if(!ns_capable(pid_ns->user_ns, CAP_SYS_BOOT))

        return-EPERM;

 

    /* For safety, we require magic arguments. */

    if(magic1 != LINUX_REBOOT_MAGIC1 ||

        (magic2 != LINUX_REBOOT_MAGIC2 &&

                    magic2 != LINUX_REBOOT_MAGIC2A &&

            magic2 != LINUX_REBOOT_MAGIC2B &&

                    magic2 != LINUX_REBOOT_MAGIC2C))

        return-EINVAL;

 

    /*

     * If pid namespaces are enabled and the current task is in a child

     * pid_namespace, the command is handled by reboot_pid_ns() which will

     * call do_exit().

     */

    ret = reboot_pid_ns(pid_ns, cmd);

    if(ret)

        returnret;

 

    /* Instead of trying to make the power_off code look like

     * halt when pm_power_off is not set do it the easy way.

     */

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

        cmd = LINUX_REBOOT_CMD_HALT;

 

    mutex_lock(&reboot_mutex);

    switch(cmd) {

    caseLINUX_REBOOT_CMD_RESTART:

        kernel_restart(NULL);

        break;

 

    caseLINUX_REBOOT_CMD_CAD_ON:

        C_A_D =1;

        break;

 

    caseLINUX_REBOOT_CMD_CAD_OFF:

        C_A_D =0;

        break;

 

    caseLINUX_REBOOT_CMD_HALT:

        kernel_halt();

        do_exit(0);

        panic(cannot halt);

 

    caseLINUX_REBOOT_CMD_POWER_OFF:

        kernel_power_off();

        do_exit(0);

        break;

 

    caseLINUX_REBOOT_CMD_RESTART2:

        if(strncpy_from_user(&buffer[0], arg, sizeof(buffer) -1) < 0) {

            ret = -EFAULT;

            break;

        }

        buffer[sizeof(buffer) -1] = '';

 

        kernel_restart(buffer);

        break;

 

#ifdef CONFIG_KEXEC

    caseLINUX_REBOOT_CMD_KEXEC:

        ret = kernel_kexec();

        break;

#endif

 

#ifdef CONFIG_HIBERNATION

    caseLINUX_REBOOT_CMD_SW_SUSPEND:

        ret = hibernate();

        break;

#endif

 

    default:

        ret = -EINVAL;

        break;

    }

    mutex_unlock(&reboot_mutex);

    returnret;

}

 

有很多分支，我们只关心kernel_power_off()和kernel_restart()两函数就行

如下：

 

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void kernel_power_off(void)

{

    kernel_shutdown_prepare(SYSTEM_POWER_OFF);//关闭外设

    if(pm_power_off_prepare)

        pm_power_off_prepare();

    migrate_to_reboot_cpu();

    syscore_shutdown();//关闭syscore

    printk(KERN_EMERG Power down.

);//关键打印

    kmsg_dump(KMSG_DUMP_POWEROFF);

    machine_power_off();

}

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void kernel_restart(char *cmd)

{

    kernel_restart_prepare(cmd);//关闭外设

    migrate_to_reboot_cpu();

    syscore_shutdown();//关闭syscore

    if(!cmd)

        printk(KERN_EMERG Restarting system.

);//关键打印

    else

        printk(KERN_EMERG Restarting system with command'%s'.

, cmd);

    kmsg_dump(KMSG_DUMP_RESTART);

    machine_restart(cmd);

}

都执行XX_prepare()函数

 

 

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static void kernel_shutdown_prepare(enumsystem_states state)

{

    blocking_notifier_call_chain(&reboot_notifier_list,

        (state == SYSTEM_HALT)?SYS_HALT:SYS_POWER_OFF, NULL);

    system_state = state;

    usermodehelper_disable();

    device_shutdown();

}

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void kernel_restart_prepare(char *cmd)

{

    blocking_notifier_call_chain(&reboot_notifier_list, SYS_RESTART, cmd);

    system_state = SYSTEM_RESTART;

    usermodehelper_disable();

    device_shutdown();

}

除了前面不同，都调用了device_shutdown()函数，关闭外设。

 

machine_power_off() machine_resestart()函数实现

 

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void machine_power_off(void)

{

    preempt_disable();

    smp_send_stop();

 

    if(pm_power_off)

        pm_power_off();//关机

}

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void machine_restart(char *cmd)

{

    preempt_disable();

    smp_send_stop();

 

    /* Flush the console to make sure all the relevant messages make it

     * out to the console drivers */

    arm_machine_flush_console();

 

    arm_pm_restart(reboot_mode, cmd);//重启

 

    /* Give a grace period for failure to restart of 1s */

    mdelay(1000);

 

    /* Whoops - the platform was unable to reboot. Tell the user! */

    printk(Reboot failed -- System halted

);

    local_irq_disable();

    while(1);

}

pm_power_offf()　arm_pm_restart()都是一个函数指针

 

赋值如下：

[kernel/drivers/power/reset/msm-poweroff.c]

 

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pm_power_off = do_msm_poweroff;

arm_pm_restart = do_msm_restart;

高通平台的关机代码与之前有所不同，现在文件msm-poweroff.c以前是restart.c。

 

do_msm_poweroff()与do_msm_restart()实现如下：

 

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static void do_msm_poweroff(void)

{

....

    pr_notice(Powering off the SoC

);//关键打印

#ifdef CONFIG_MSM_DLOAD_MODE

    set_dload_mode(0);//关机，所以dloadmode是0

#endif

    qpnp_pon_system_pwr_off(PON_POWER_OFF_SHUTDOWN);//配置PMIC,是关机

.....

    /* MSM initiated power off, lower ps_hold */

    __raw_writel(0, msm_ps_hold);//拉　PS＿HOLD,执行关机动作。

 

    mdelay(10000);

    pr_err(Powering off has failed

);

    return;

}

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static void do_msm_restart(enumreboot_mode reboot_mode, constchar *cmd)

...

 

    pr_notice(Going downfor restart now

);//关键打印

 

    msm_restart_prepare(cmd);//重启准备前动作

 

#ifdef CONFIG_MSM_DLOAD_MODE

    /*

     * Trigger a watchdog bite here and if this fails,

     * device will take the usual restart path.

     */

 

    if(WDOG_BITE_ON_PANIC && in_panic)

        msm_trigger_wdog_bite();

#endif

 

....

    halt_spmi_pmic_arbiter();

    __raw_writel(0, msm_ps_hold);//拉PS＿HOLD重启

 

    mdelay(10000);

}

msm_restart_prepare()实现

 

 

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static void msm_restart_prepare(constchar *cmd)

{

#ifdef CONFIG_MSM_DLOAD_MODE

 

    /* Write download mode flags if we're panic'ing

     * Write download mode flags if restart_mode says so

     * Kill download mode if master-kill switch is set

     */

 

    set_dload_mode(download_mode &&

            (in_panic || restart_mode == RESTART_DLOAD));//设置dload

#endif

 

    /* Hard reset the PMIC unless memory contents must be maintained. */

    if(get_dload_mode() || (cmd != NULL && cmd[0] !=''))

        qpnp_pon_system_pwr_off(PON_POWER_OFF_WARM_RESET);//设置PIMC为热重启

    else

        qpnp_pon_system_pwr_off(PON_POWER_OFF_HARD_RESET);//设置PIMC为硬重启

 

    if(cmd != NULL) {

        if(!strncmp(cmd, bootloader, 10)) {

            __raw_writel(0x77665500, restart_reason);//写一些东东到IMEM，用于bootloader,recovery等

        }else if(!strncmp(cmd, recovery, 8)) {

            __raw_writel(0x77665502, restart_reason);

        }else if(!strcmp(cmd, rtc)) {

            __raw_writel(0x77665503, restart_reason);

        }else if(!strncmp(cmd, oem-, 4)) {

            unsignedlong code;

            intret;

            ret = kstrtoul(cmd +4, 16, &code);

            if(!ret)

                __raw_writel(0x6f656d00| (code & 0xff),

                         restart_reason);

        }else if(!strncmp(cmd, edl, 3)) {

            enable_emergency_dload_mode();

        }else {

            __raw_writel(0x77665501, restart_reason);

        }

    }

 

.....

 

}

 

 

do_msm_poweroff()与do_msm_restart()都设置了dload,PMIC，唯一不同的是do_msm_restart()里多了一个__raw_writel的动作，即reason写入IMEM,目的在于重启进入sbl1时判断应该进入那种模式，如我们开发用的bootloader模式，恢复出厂设置的recovery模式等。