syzkaller has found reproducer for the following crash on  
f3b5ad89de16f5d42e8ad36fbdf85f705c1ae051
git://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/master
compiler: gcc (GCC) 7.1.1 20170620
.config is attached
Raw console output is attached.
C reproducer is attached
syzkaller reproducer is attached. See https://goo.gl/kgGztJ
for information about syzkaller reproducers


BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=0 stuck for 37s!
BUG: workqueue lockup - pool cpus=1 node=0 flags=0x0 nice=-20 stuck for 32s!
Showing busy workqueues and worker pools:
workqueue events: flags=0x0
   pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256
     pending: cache_reap
workqueue events_power_efficient: flags=0x80
   pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=2/256
     pending: neigh_periodic_work, do_cache_clean
workqueue mm_percpu_wq: flags=0x8
   pwq 2: cpus=1 node=0 flags=0x0 nice=0 active=1/256
     pending: vmstat_update
workqueue kblockd: flags=0x18
   pwq 3: cpus=1 node=0 flags=0x0 nice=-20 active=1/256
     pending: blk_timeout_work