panic when reboot the system

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. Perhaps this is a bug and trigger it like this and the latest kernel maybe also have the problem.

use a lot of memory
wake up kswapd()
reclaim some pages from init thread (pid=1)
reboot
shutdown the disk
init thread read data from disk
page fault, because the page has already reclaimed
receive SIGBUS, and init thread exit
trigger the panic

Thanks,
Xishi Qiu

Interesting. 3.4 is a pretty old kernel but I expect at least some of this remains.

- Why the heck did the disk get shut down while init still had pages on it? We shouldn't be able to get that far without having done a swapoff.

- Ignoring the above, as far as I can tell a regular old I/O error during pagein of one of init's pages (anon or file-backed) will result in the delivery of SIGBUS to init. If init isn't catching SIGBUS (or if init's signal-handling code is also swapped out to a bad sector??) then we're going to kill init and the system will panic as above.

I'm not sure what we can do in this situation - init has permanently lost some text or data and is hence dead. But panicing the system doesn't seem the correct response.

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