syzbot has bisected this issue to:

commit 68e9dc29f8f42c79d2a3755223ed910ce36b4ae2
Author: Yuyang Du [off-list ref]
Date:   Mon May 6 08:19:36 2019 +0000

    locking/lockdep: Check redundant dependency only when CONFIG_LOCKDEP_SMALL

bisection log:  https://syzkaller.appspot.com/x/bisect.txt?x=12f2bda8300000
start commit:   ad347abe Merge tag 'trace-v5.13-rc5-2' of git://git.kernel..
git tree:       upstream
final oops:     https://syzkaller.appspot.com/x/report.txt?x=11f2bda8300000
console output: https://syzkaller.appspot.com/x/log.txt?x=16f2bda8300000
kernel config:  https://syzkaller.appspot.com/x/.config?x=30f476588412c065
dashboard link: https://syzkaller.appspot.com/bug?extid=99043e2052d9c50c81fc
syz repro:      https://syzkaller.appspot.com/x/repro.syz?x=1204231fd00000
C reproducer:   https://syzkaller.appspot.com/x/repro.c?x=1324e4d0300000

Reported-by: syzbot+99043e2052d9c50c81fc@syzkaller.appspotmail.com
Fixes: 68e9dc29f8f4 ("locking/lockdep: Check redundant dependency only when CONFIG_LOCKDEP_SMALL")

For information about bisection process see: https://goo.gl/tpsmEJ#bisection