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

[Rui Xiang]

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.