以上这些只有前六个命令被Android系统所使用，为什么这么说，可以去看bionic/libc/include/sys/reboot.h，上边已经贴出了。LINUX_REBOOT_CMD_HALT虽有定义，但是也没有发现Android系统中哪里有调用，有高手找到的话，希望能够告知一下。最终的最终，能够用到的就只有三个：
- RESTART
- POWER_OFF
-
RESTART2
10.最终实现
重启调用的是kernel_restart，区别是参数是不是空，关机则调用kernel_power_off()，先看关机：/** * kernel_power_off - power_off the system * * Shutdown everything and perform a clean system power_off. */ void kernel_power_off(void) { kernel_shutdown_prepare(SYSTEM_POWER_OFF); if (pm_power_off_prepare) pm_power_off_prepare(); disable_nonboot_cpus(); syscore_shutdown(); printk(KERN_EMERG "Power down.n"); kmsg_dump(KMSG_DUMP_POWEROFF); machine_power_off(); } EXPORT_SYMBOL_GPL(kernel_power_off);最了一系列准备工作，最终调用machine_power_off()：
void machine_power_off(void) { machine_shutdown(); if (pm_power_off) pm_power_off(); }之前找寻的pm_power_off在这里就有用处了，是关机的最后一步操作。关机完成，之后看下重启操作：
/** * kernel_restart - reboot the system * @cmd: pointer to buffer containing command to execute for restart * or %NULL * * Shutdown everything and perform a clean reboot. * This is not safe to call in interrupt context. */ void kernel_restart(char *cmd) { kernel_restart_prepare(cmd); if (!cmd) printk(KERN_EMERG "Restarting system.n"); else printk(KERN_EMERG "Restarting system with command '%s'.n", cmd); kmsg_dump(KMSG_DUMP_RESTART); machine_restart(cmd); } EXPORT_SYMBOL_GPL(kernel_restart);
