首页 > 代码库 > android L 关机流程图

android L 关机流程图

下面是简单的流程图,从java到kernel层。


技术分享



ShutdownThread.java文件

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

代码如下:


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:


        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:


            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:

                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:

        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]

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]

        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:

    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:

        // Set initial variables and time out time.
        mActionDone = false;
        final long endShutTime = SystemClock.elapsedRealtime() + MAX_SHUTDOWN_WAIT_TIME;
        synchronized (mActionDoneSync) {
            try {
                final IMountService mount = IMountService.Stub.asInterface(
                        ServiceManager.checkService("mount"));
                if (mount != null) {
                    mount.shutdown(observer);
                } else {
                    Log.w(TAG, "MountService unavailable for shutdown");
                }
            } catch (Exception e) {
                Log.e(TAG, "Exception during MountService shutdown", e);
            }
            while (!mActionDone) {
                long delay = 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:


    public static void rebootOrShutdown(boolean reboot, 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

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]

KEYWORD(powerctl,    COMMAND, 1, do_powerctl)

do_powerctl的实现

代码如下:

[system/core/init/builtins.c]

int do_powerctl(int nargs, char **args)
{
....

    return android_reboot(cmd, 0, reboot_target);
}

它调用android_reboot()函数,实现如下:


[system/core/libcutils/android_reboot.c]

int android_reboot(int cmd, int flags UNUSED, char *arg)
{
    int ret;

    sync();
    remount_ro();

    switch (cmd) {
        case ANDROID_RB_RESTART:
            ret = reboot(RB_AUTOBOOT);
            break;

        case ANDROID_RB_POWEROFF:
            ret = reboot(RB_POWER_OFF);
            break;

        case ANDROID_RB_RESTART2:
            ret = syscall(__NR_reboot, LINUX_REBOOT_MAGIC1, LINUX_REBOOT_MAGIC2,
                           LINUX_REBOOT_CMD_RESTART2, arg);
            break;

        default:
            ret = -1;
    }

    return ret;
}

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]

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]

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]

 #define __NR_reboot 142

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]

#define __NR_reboot 142
__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]

SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
		void __user *, arg)
{
	struct pid_namespace *pid_ns = task_active_pid_ns(current);
	char buffer[256];
	int ret = 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)
		return ret;

	/* 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) {
	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();
		do_exit(0);
		panic("cannot halt");

	case LINUX_REBOOT_CMD_POWER_OFF:
		kernel_power_off();
		do_exit(0);
		break;

	case LINUX_REBOOT_CMD_RESTART2:
		if (strncpy_from_user(&buffer[0], arg, sizeof(buffer) - 1) < 0) {
			ret = -EFAULT;
			break;
		}
		buffer[sizeof(buffer) - 1] = '\0';

		kernel_restart(buffer);
		break;

#ifdef CONFIG_KEXEC
	case LINUX_REBOOT_CMD_KEXEC:
		ret = kernel_kexec();
		break;
#endif

#ifdef CONFIG_HIBERNATION
	case LINUX_REBOOT_CMD_SW_SUSPEND:
		ret = hibernate();
		break;
#endif

	default:
		ret = -EINVAL;
		break;
	}
	mutex_unlock(&reboot_mutex);
	return ret;
}


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

如下:

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.\n");//关键打印
	kmsg_dump(KMSG_DUMP_POWEROFF);
	machine_power_off();
}
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.\n");//关键打印
	else
		printk(KERN_EMERG "Restarting system with command '%s'.\n", cmd);
	kmsg_dump(KMSG_DUMP_RESTART);
	machine_restart(cmd);
}

都执行XX_prepare()函数

static void kernel_shutdown_prepare(enum system_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();
}

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

void machine_power_off(void)
{
	preempt_disable();
	smp_send_stop();

	if (pm_power_off)
		pm_power_off();//关机
}

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\n");
	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]

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:

static void do_msm_poweroff(void)
{
....
	pr_notice("Powering off the SoC\n");//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\n");
	return;
}

static void do_msm_restart(enum reboot_mode reboot_mode, const char *cmd)
...

	pr_notice("Going down for restart now\n");//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

static void msm_restart_prepare(const char *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] != '\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)) {
			unsigned long code;
			int ret;
			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。


完了






android L 关机流程图