FYI, we noticed the following commit (built with gcc-4.9):

commit: a94b9367e044ba672c9f4105eb1516ff6ff4948a ("ipv6: grab rt->rt6i_ref before allocating pcpu rt")
https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git master

in testcase: boot

on test machine: qemu-system-x86_64 -enable-kvm -smp 2 -m 512M

caused below changes (please refer to attached dmesg/kmsg for entire log/backtrace):


+--------------------------------------------+------------+------------+
|                                            | 2b760fcf5c | a94b9367e0 |
+--------------------------------------------+------------+------------+
| boot_successes                             | 8          | 4          |
| boot_failures                              | 0          | 4          |
| BUG:using_smp_processor_id()in_preemptible | 0          | 4          |
+--------------------------------------------+------------+------------+



[   28.927206] BUG: using smp_processor_id() in preemptible [00000000] code: odhcpd/1011
[   28.928424] caller is debug_smp_processor_id+0x17/0x19
[   28.929085] CPU: 1 PID: 1011 Comm: odhcpd Not tainted 4.14.0-rc3-00908-ga94b936 #1
[   28.930196] Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
[   28.931421] Call Trace:
[   28.931765]  dump_stack+0x85/0xbe
[   28.932244]  check_preemption_disabled+0xdb/0xed
[   28.932845]  debug_smp_processor_id+0x17/0x19
[   28.933421]  ip6_pol_route+0x541/0x607
[   28.933993]  ip6_pol_route_output+0x11/0x13
[   28.934547]  fib6_rule_action+0xbf/0x1ff
[   28.935088]  ? ip6_pol_route_input+0x17/0x17
[   28.935725]  fib_rules_lookup+0x18e/0x245
[   28.936255]  ? fib_rules_lookup+0x18e/0x245
[   28.936819]  ? ip6_pol_route_input+0x17/0x17
[   28.937404]  fib6_rule_lookup+0x5a/0xe9
[   28.937944]  ? ip6_pol_route_input+0x17/0x17
[   28.938579]  ip6_route_output_flags+0xd0/0xdc
[   28.939147]  ip6_dst_lookup_tail+0x57/0x1aa
[   28.939748]  ip6_dst_lookup_flow+0x33/0x73
[   28.940347]  ip6_datagram_dst_update+0x25b/0x4c2
[   28.940947]  ? save_stack_trace+0x16/0x18
[   28.941697]  __ip6_datagram_connect+0x218/0x2ba
[   28.942286]  ? __ip6_datagram_connect+0x218/0x2ba
[   28.942897]  ? __local_bh_enable_ip+0x87/0xa8
[   28.943471]  ? lock_sock_nested+0x42/0x90
[   28.944080]  ip6_datagram_connect+0x26/0x3a
[   28.944634]  ip6_datagram_connect_v6_only+0x14/0x16
[   28.945296]  inet_dgram_connect+0x4a/0x64
[   28.945815]  SyS_connect+0x7e/0xbf
[   28.946373]  ? __might_fault+0x79/0x7f
[   28.946934]  compat_SyS_socketcall+0x113/0x219
[   28.947797]  ? do_int80_syscall_32+0x22/0x1c1
[   28.948438]  ? trace_hardirqs_on_caller+0x174/0x190
[   28.949063]  do_int80_syscall_32+0x74/0x1c1
[   28.949664]  entry_INT80_compat+0x32/0x50
[   28.950269] RIP: 0023:0xf7ef2384
[   28.950735] RSP: 002b:00000000ffa89318 EFLAGS: 00000296 ORIG_RAX: 0000000000000066
[   28.951736] RAX: ffffffffffffffda RBX: 0000000000000003 RCX: 00000000ffa89328
[   28.952670] RDX: 00000000f7f38000 RSI: 00000000ffa89328 RDI: 00000000ffa89440
[   28.953572] RBP: 00000000ffa89388 R08: 0000000000000000 R09: 0000000000000000
[   28.954538] R10: 0000000000000000 R11: 0000000000000000 R12: 0000000000000000
[   28.955533] R13: 0000000000000000 R14: 0000000000000000 R15: 0000000000000000

Elapsed time: 30

initrds=(
	/osimage/openwrt/openwrt-i386-2016-03-16.cgz
	/lkp/scheduled/vm-lkp-nex04-openwrt-ia32-27/boot-1-openwrt-i386-2016-03-16.cgz-a94b9367e044ba672c9f4105eb1516ff6ff4948a-20171009-12855-139piyy-0.cgz
	/lkp/lkp/lkp-i386.cgz
)

cat "${initrds[@]}" > /fs/sdb1/initrd-vm-lkp-nex04-openwrt-ia32-27

kvm=(
	qemu-system-x86_64
	-enable-kvm
	-kernel /pkg/linux/x86_64-randconfig-h0-10091308/gcc-4.9/a94b9367e044ba672c9f4105eb1516ff6ff4948a/vmlinuz-4.14.0-rc3-00908-ga94b936
	-initrd /fs/sdb1/initrd-vm-lkp-nex04-openwrt-ia32-27
	-m 512
	-smp 2
	-device e1000,netdev=net0
	-netdev user,id=net0,hostfwd=tcp::23296-:22
	-boot order=nc
	-no-reboot
	-watchdog i6300esb
	-watchdog-action debug
	-rtc base=localtime
	-pidfile /dev/shm/kboot/pid-vm-lkp-nex04-openwrt-ia32-27
	-serial file:/dev/shm/kboot/vm-lkp-nex04-openwrt-ia32-27/serial
	-serial file:/dev/shm/kboot/vm-lkp-nex04-openwrt-ia32-27/kmsg
	-daemonize
	-display none
	-monitor null
)

append=(
	ip=::::vm-lkp-nex04-openwrt-ia32-27::dhcp
	root=/dev/ram0
	user=lkp
	job=/lkp/scheduled/vm-lkp-nex04-openwrt-ia32-27/boot-1-openwrt-i386-2016-03-16.cgz-a94b9367e044ba672c9f4105eb1516ff6ff4948a-20171009-12855-139piyy-0.yaml
	ARCH=x86_64
	kconfig=x86_64-randconfig-h0-10091308
	branch=linux-devel/devel-spot-201710090350
	commit=a94b9367e044ba672c9f4105eb1516ff6ff4948a
	BOOT_IMAGE=/pkg/linux/x86_64-randconfig-h0-10091308/gcc-4.9/a94b9367e044ba672c9f4105eb1516ff6ff4948a/vmlinuz-4.14.0-rc3-00908-ga94b936
	max_uptime=600
	RESULT_ROOT=/result/boot/1/vm-lkp-nex04-openwrt-ia32/openwrt-i386-2016-03-16.cgz/x86_64-randconfig-h0-10091308/gcc-4.9/a94b9367e044ba672c9f4105eb1516ff6ff4948a/0
	LKP_SERVER=inn
	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


To reproduce:

        git clone https://github.com/intel/lkp-tests.git
        cd lkp-tests
        bin/lkp qemu -k <bzImage> job-script  # job-script is attached in this email



Thanks,
Xiaolong