INFO: task hung in switchdev_deferred_process_work

[syzbot]

Hello,

syzbot hit the following crash on net-next commit
cf1a1e07fc8bb29947ad3c9568d73aee3f851431 (Fri Apr 20 11:18:16 2018 +0000)
tun: do not compute the rxhash, if not needed
syzbot dashboard link:
https://syzkaller.appspot.com/bug?extid=047726d6b8ddceb70647

Unfortunately, I don't have any reproducer for this crash yet.
Raw console output:
https://syzkaller.appspot.com/x/log.txt?id=6544155694071808
Kernel config:
https://syzkaller.appspot.com/x/.config?id=-8412024688694752032
compiler: gcc (GCC) 8.0.1 20180413 (experimental)
CC: [christia...@ubuntu.com da...@davemloft.net dsa...@gmail.com
f...@strlen.de jb...@redhat.com ktk...@virtuozzo.com
linux-...@vger.kernel.org lucie...@gmail.com
msch...@universe-factory.net net...@vger.kernel.org vyas...@gmail.com]

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: syzbot+047726...@syzkaller.appspotmail.com
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INFO: task kworker/1:2:1978 blocked for more than 120 seconds.
Not tainted 4.16.0+ #10
"echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message.
kworker/1:2 D22952 1978 2 0x80000000
Workqueue: events switchdev_deferred_process_work
Call Trace:
context_switch kernel/sched/core.c:2848 [inline]
__schedule+0x801/0x1e30 kernel/sched/core.c:3490
schedule+0xef/0x430 kernel/sched/core.c:3549
schedule_preempt_disabled+0x10/0x20 kernel/sched/core.c:3607
__mutex_lock_common kernel/locking/mutex.c:833 [inline]
__mutex_lock+0xe38/0x17f0 kernel/locking/mutex.c:893
mutex_lock_nested+0x16/0x20 kernel/locking/mutex.c:908
rtnl_lock+0x17/0x20 net/core/rtnetlink.c:74
switchdev_deferred_process_work+0xe/0x20 net/switchdev/switchdev.c:150
process_one_work+0xc1e/0x1b50 kernel/workqueue.c:2145
worker_thread+0x1cc/0x1440 kernel/workqueue.c:2279
kthread+0x345/0x410 kernel/kthread.c:238
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:411

Showing all locks held in the system:
2 locks held by khungtaskd/891:
#0: 000000001a262294 (rcu_read_lock){....}, at:
check_hung_uninterruptible_tasks kernel/hung_task.c:175 [inline]
#0: 000000001a262294 (rcu_read_lock){....}, at: watchdog+0x1ff/0xf60
kernel/hung_task.c:249
#1: 000000004b99efda (tasklist_lock){.+.+}, at:
debug_show_all_locks+0xde/0x34a kernel/locking/lockdep.c:4470
3 locks held by kworker/1:2/1978:
#0: 00000000a4bea400 ((wq_completion)"events"){+.+.}, at:
__write_once_size include/linux/compiler.h:215 [inline]
#0: 00000000a4bea400 ((wq_completion)"events"){+.+.}, at:
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: 00000000a4bea400 ((wq_completion)"events"){+.+.}, at: atomic64_set
include/asm-generic/atomic-instrumented.h:40 [inline]
#0: 00000000a4bea400 ((wq_completion)"events"){+.+.}, at: atomic_long_set
include/asm-generic/atomic-long.h:57 [inline]
#0: 00000000a4bea400 ((wq_completion)"events"){+.+.}, at: set_work_data
kernel/workqueue.c:617 [inline]
#0: 00000000a4bea400 ((wq_completion)"events"){+.+.}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
#0: 00000000a4bea400 ((wq_completion)"events"){+.+.}, at:
process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116
#1: 00000000c5de1f0b (deferred_process_work){+.+.}, at:
process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120
#2: 00000000005611a7 (rtnl_mutex){+.+.}, at: rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
2 locks held by getty/4475:
#0: 0000000097ac52d9 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 000000003b972d25 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4476:
#0: 000000003c3e2689 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 00000000496b5a4f (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4477:
#0: 00000000c40886da (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 000000006587d58b (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4478:
#0: 00000000ab850933 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 00000000f0235c4f (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4479:
#0: 00000000d99cd33d (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 00000000779082e0 (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4480:
#0: 000000001f27ece1 (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 0000000056411bec (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
2 locks held by getty/4481:
#0: 000000006a90a03b (&tty->ldisc_sem){++++}, at:
ldsem_down_read+0x37/0x40 drivers/tty/tty_ldsem.c:365
#1: 0000000084f5df3c (&ldata->atomic_read_lock){+.+.}, at:
n_tty_read+0x321/0x1cc0 drivers/tty/n_tty.c:2131
3 locks held by kworker/0:4/5295:
#0: 000000007e632e35 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at:
__write_once_size include/linux/compiler.h:215 [inline]
#0: 000000007e632e35 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at:
arch_atomic64_set arch/x86/include/asm/atomic64_64.h:34 [inline]
#0: 000000007e632e35 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at:
atomic64_set include/asm-generic/atomic-instrumented.h:40 [inline]
#0: 000000007e632e35 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at:
atomic_long_set include/asm-generic/atomic-long.h:57 [inline]
#0: 000000007e632e35 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at:
set_work_data kernel/workqueue.c:617 [inline]
#0: 000000007e632e35 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at:
set_work_pool_and_clear_pending kernel/workqueue.c:644 [inline]
#0: 000000007e632e35 ((wq_completion)"%s"("ipv6_addrconf")){+.+.}, at:
process_one_work+0xaef/0x1b50 kernel/workqueue.c:2116
#1: 00000000674d002f ((addr_chk_work).work){+.+.}, at:
process_one_work+0xb46/0x1b50 kernel/workqueue.c:2120
#2: 00000000005611a7 (rtnl_mutex){+.+.}, at: rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
1 lock held by syz-executor7/32060:
#0: 00000000e82e11a2 (ipvs->sync_mutex){+.+.}, at:
do_ip_vs_set_ctl+0x339/0x1d30 net/netfilter/ipvs/ip_vs_ctl.c:2393
2 locks held by syz-executor7/32066:
#0: 00000000005611a7 (rtnl_mutex){+.+.}, at: rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74
#1: 00000000e82e11a2 (ipvs->sync_mutex){+.+.}, at:
do_ip_vs_set_ctl+0x562/0x1d30 net/netfilter/ipvs/ip_vs_ctl.c:2388
1 lock held by ipvs-b:3:0/32063:
#0: 00000000005611a7 (rtnl_mutex){+.+.}, at: rtnl_lock+0x17/0x20
net/core/rtnetlink.c:74

=============================================

NMI backtrace for cpu 0
CPU: 0 PID: 891 Comm: khungtaskd Not tainted 4.16.0+ #10
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS
Google 01/01/2011
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x1b9/0x294 lib/dump_stack.c:113
nmi_cpu_backtrace.cold.4+0x19/0xce lib/nmi_backtrace.c:103
nmi_trigger_cpumask_backtrace+0x151/0x192 lib/nmi_backtrace.c:62
arch_trigger_cpumask_backtrace+0x14/0x20 arch/x86/kernel/apic/hw_nmi.c:38
trigger_all_cpu_backtrace include/linux/nmi.h:138 [inline]
check_hung_task kernel/hung_task.c:132 [inline]
check_hung_uninterruptible_tasks kernel/hung_task.c:190 [inline]
watchdog+0xc10/0xf60 kernel/hung_task.c:249
kthread+0x345/0x410 kernel/kthread.c:238
ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:411
Sending NMI from CPU 0 to CPUs 1:
NMI backtrace for cpu 1 skipped: idling at native_safe_halt+0x6/0x10
arch/x86/include/asm/irqflags.h:54


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