/****************************************************************************
 *                  I.MX6 android shutdown 内核崩溃
 * 说明：
 *     本文主要是记录解决I.MX6的关机会进入halt模式，导致内核崩溃。
 *
 *                                        2016-3-24 深圳 南山平山村 曾剑锋
 ***************************************************************************/

一、参考文章：
    android 关机 流程分析 
        http://blog.chinaunix.net/uid-24227137-id-3248111.html

二、 现象：
    SysRq : Emergency Remount R/O
    EXT4-fs (mmcblk0p4): re-mounted. Opts: (null)
    EXT4-fs (mmcblk0p6): re-mounted. Opts: (null)
    Emergency Remount complete
    System halted.
    BUG: soft lockup - CPU#1 stuck for 23s! [Thread-88:3327]
    Modules linked in:
    
    Pid: 3327, comm:            Thread-88
    CPU: 1    Not tainted  (3.0.35 #617)
    PC is at machine_halt+0x8/0xc
    LR is at smp_send_stop+0x9c/0xc4
    pc : [<c004d7dc>]    lr : [<c0052f98>]    psr: 60000013
    sp : d0e53e88  ip : 00000000  fp : 78393c6c
    r10: 00000000  r9 : d0e52000  r8 : c004ca84
    r7 : 00000000  r6 : 4321fedc  r5 : 28121969  r4 : 4321fedc
    r3 : 00000001  r2 : 00000001  r1 : 00000000  r0 : 00000001
    Flags: nZCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment user
    Control: 10c53c7d  Table: 24fa804a  DAC: 00000015
    
    PC: 0xc004d75c:
    d75c  e5843004 eaffffda eb01b99d e3500000 1affffed e5973004 e12fff33 e10f3000
    d77c  e3130080 1a000003 f1080080 eaffffd4 eb19c101 eaffffe0 e59f0018 e3a010fa
    d79c  eb0101fd f1080080 eaffffcd c06dccf4 c0a0ce64 c09886b4 c085477c e1a0200d

三、 解决方法：
    cat kernel/sys.c
    /*
     * Reboot system call: for obvious reasons only root may call it,
     * and even root needs to set up some magic numbers in the registers
     * so that some mistake won't make this reboot the whole machine.
     * You can also set the meaning of the ctrl-alt-del-key here.
     *
     * reboot doesn't sync: do that yourself before calling this.
     */
    SYSCALL_DEFINE4(reboot, int, magic1, int, magic2, unsigned int, cmd,
            void __user *, arg)
    {
        ......
        //if ((cmd == LINUX_REBOOT_CMD_POWER_OFF) && !pm_power_off)
        //    cmd = LINUX_REBOOT_CMD_HALT;
        ......
    }