Re: [sysvinit-devel] [Question] A panic when reboot --force the system

[Scott James Remnant]

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> On Oct 23, 2015, at 2:45 AM, Rui Xiang <address@hidden> wrote:
> 
> Hi，list
> 
> I encounter a panic about init process.
> 
> Kernel panic - not syncing: Attempted to kill init! exitcode=0x00000007
> 
> Pid: 1, comm: init Tainted: G  R        O 3.4.24.19-0.11-default #1
> Call Trace:
> [<ffffffff8144dd24>] panic+0xc1/0x1e2
> [<ffffffff8104483b>] do_exit+0x7db/0x8d0
> [<ffffffff81044c7a>] do_group_exit+0x3a/0xa0
> [<ffffffff8105394b>] get_signal_to_deliver+0x1ab/0x5e0
> [<ffffffff81002270>] do_signal+0x60/0x5f0
> [<ffffffff8145bf97>] ? do_page_fault+0x4a7/0x4d0
> [<ffffffff81170d2c>] ? poll_select_copy_remaining+0xec/0x140
> [<ffffffff81002885>] do_notify_resume+0x65/0x80
> [<ffffffff8124ca7e>] ? trace_hardirqs_on_thunk+0x3a/0x3c
> [<ffffffff814587ab>] retint_signal+0x4d/0x92
> 
> The system has a little memory left, then reboot it, and get the panic.
> 
> In our host, kswapd would be wake up while using a lot of memory, and then 
> reclaim
> some pages from init process. If we execute *"reboot"* or *"reboot -f"* to 
> reboot
> host through sysvinit, reboot process will call sys_reboot and shut down the 
> sas
> driver(disk), then will trigger the panic of init process.
> 
> As follow,
> 
>        HOST                    reboot process            init process
> use a lot of memory
> wake up kswapd
>   reclaim some pages
>   (these pages are code segment
>    or data segment of init process)
>   from init thread (pid=1)
>                                reboot
>                                  sys_reboot
>                                    shutdown disk driver
>                                                        init thread read data 
> from disk
>                                                          page_fault
>                                                            filemap_fault
>                                                              readpage failed 
> because the disk is closed
>                                                            return 
> VM_FAULT_SIGBUS
>                                                            send signal SIGBUS
>                                                          do_signal
>                                                            do_exit
>                                                            trigger the panic
> 
> 
> It seems that reboot or force reboot through *sysvinit* have the problem.
> Furthermore, using reboot -f in *systemd* should also have this problem, 
> right?
> 
> And is that a bug for current reboot process in sysvinit or systemd?
> 
> All comments are welcome, thanks.
> 
>