linux-kernel - Re: [lockdep] b09be676e0 BUG: unable to handle kernel NULL pointer dereference at 000001f2

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Date:   Thu, 12 Oct 2017 17:21:55 +0800
From:   Fengguang Wu <fengguang.wu@...el.com>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Byungchul Park <byungchul.park@....com>,
        Ingo Molnar <mingo@...nel.org>, linux-kernel@...r.kernel.org,
        LKP <lkp@...org>, Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [lockdep] b09be676e0 BUG: unable to handle kernel NULL pointer
 dereference at 000001f2

On Thu, Oct 12, 2017 at 10:47:25AM +0200, Peter Zijlstra wrote:
>On Tue, Oct 03, 2017 at 10:06:34PM +0800, Fengguang Wu wrote:
>
>> #!/bin/bash
>>
>> kernel=$1
>> initrd=openwrt-trinity-i386.cgz
>>
>> wget --no-clobber https://github.com/fengguang/reproduce-kernel-bug/raw/master/initrd/$initrd
>>
>> kvm=(
>> 	qemu-system-x86_64
>> 	-enable-kvm
>> 	-cpu Haswell,+smep
>> 	-kernel $kernel
>> 	-initrd $initrd
>> 	-m 256
>> 	-smp 1
>> 	-device e1000,netdev=net0
>> 	-netdev user,id=net0
>> 	-boot order=nc
>> 	-no-reboot
>> 	-watchdog i6300esb
>> 	-watchdog-action debug
>> 	-rtc base=localtime
>> 	-serial stdio
>> 	-display none
>> 	-monitor null
>> )
>>
>> append=(
>> 	root=/dev/ram0
>> 	hung_task_panic=1
>> 	debug
>> 	apic=debug
>> 	sysrq_always_enabled
>> 	rcupdate.rcu_cpu_stall_timeout=100
>> 	net.ifnames=0
>> 	printk.devkmsg=on
>> 	panic=-1
>> 	softlockup_panic=1
>> 	nmi_watchdog=panic
>> 	oops=panic
>> 	load_ramdisk=2
>> 	prompt_ramdisk=0
>> 	drbd.minor_count=8
>> 	systemd.log_level=err
>> 	ignore_loglevel
>> 	console=tty0
>> 	earlyprintk=ttyS0,115200
>> 	console=ttyS0,115200
>> 	vga=normal
>> 	rw
>> 	drbd.minor_count=8
>> )
>>
>> "${kvm[@]}" -append "${append[*]}"
>
>
>So I was wanting to go chase that one splat you triggered, but the above
>(after s/Haswell,+smep/host/) boots right up until it wants an init:
>
>[    0.000000] Kernel command line: root=/dev/ram0 hung_task_panic=1 debug apic=debug sysrq_always_enabled rcupdate.rcu_cpu_stall_timeout=100 net.ifnames=0 printk.devkmsg=on panic=-1 softlockup_panic=1 nmi_watchdog=panic oops=panic load_ramdisk=2 prompt_ramdisk=0 drbd.minor_count=8 systemd.log_level=err ignore_loglevel console=tty0 earlyprintk=ttyS0,115200 console=ttyS0,115200 vga=normal rw drbd.minor_count=8
>
>[   35.721719] Kernel panic - not syncing: No working init found.  Try passing init= option to kernel. See Linux Documentation/admin-guide/init.rst for guidance.

Well I got the same result. The script and initrd image matches well
with my local version. I'll dig what goes wrong.

>And it did download that initrd thingy...
>
>$ shasum openwrt-trinity-i386.cgz
>0a405d02a162defd82a5ffd556fd24e0ee2f994a  openwrt-trinity-i386.cgz
>
>
>Anything else I need?
>