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android L 关机流程图
下面是简单的流程图,从java到kernel层。
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)
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; }
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); } } ..... }
完了
android L 关机流程图