Re: WARNING in lockdep_unregister_key

[syzbot]

syzbot has bisected this bug to:

commit 009bb421b6ceb7916ce627023d0eb7ced04c8910
Author: Bart Van Assche <bvanassche@xxxxxxx>
Date:   Sun Mar 3 22:00:46 2019 +0000

    workqueue, lockdep: Fix an alloc_workqueue() error path

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=1625a027200000
start commit:   009bb421 workqueue, lockdep: Fix an alloc_workqueue() erro..
git tree:       upstream
final crash:    https://syzkaller.appspot.com/x/report.txt?x=1525a027200000
console output: https://syzkaller.appspot.com/x/log.txt?x=1125a027200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=e9d91b7192a5e96e
dashboard link: https://syzkaller.appspot.com/bug?extid=be0c198232f86389c3dd
userspace arch: amd64
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1006dc83200000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=137d0027200000

Reported-by: syzbot+be0c198232f86389c3dd@xxxxxxxxxxxxxxxxxxxxxxxxx
Fixes: 009bb421 ("workqueue, lockdep: Fix an alloc_workqueue() error path")