Subject: BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!

From: syzbot <[email-masked]>
Date: Wed, 06 Mar 2019 10:04:04 -0800

Hello,

syzbot found the following crash on:

HEAD commit:    cf08baa29613 Add linux-next specific files for 20190306
git tree:       linux-next
console output: https://syzkaller.appspot.com/x/log.txt?x=15bc76c7200000
kernel config:  https://syzkaller.appspot.com/x/.config?x=c8b6073d992e8217
dashboard link: https://syzkaller.appspot.com/bug?extid=91fd909b6e62ebe06131
compiler:       gcc (GCC) 9.0.0 20181231 (experimental)

Unfortunately, I don't have any reproducer for this crash yet.

IMPORTANT: if you fix the bug, please add the following tag to the commit:
Reported-by: [email-masked]

BUG: MAX_LOCKDEP_CHAIN_HLOCKS too low!
turning off the locking correctness validator.
CPU: 0 PID: 11902 Comm: kworker/u5:27 Not tainted 5.0.0-next-20190306 #4
Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS  
Google 01/01/2011
Workqueue: hci94 hci_power_on
Call Trace:
  __dump_stack lib/dump_stack.c:77 [inline]
  dump_stack+0x172/0x1f0 lib/dump_stack.c:113
  add_chain_cache kernel/locking/lockdep.c:2582 [inline]
  lookup_chain_cache_add kernel/locking/lockdep.c:2656 [inline]
  validate_chain kernel/locking/lockdep.c:2676 [inline]
  __lock_acquire.cold+0x250/0x50d kernel/locking/lockdep.c:3692
  lock_acquire+0x16f/0x3f0 kernel/locking/lockdep.c:4202
  __flush_work+0x677/0x8a0 kernel/workqueue.c:3034
  flush_work+0x18/0x20 kernel/workqueue.c:3060
  hci_dev_do_open+0xa92/0x1780 net/bluetooth/hci_core.c:1543
  hci_power_on+0x10d/0x580 net/bluetooth/hci_core.c:2173
  process_one_work+0x98e/0x1790 kernel/workqueue.c:2269
  worker_thread+0x98/0xe40 kernel/workqueue.c:2415
  kthread+0x357/0x430 kernel/kthread.c:253
  ret_from_fork+0x3a/0x50 arch/x86/entry/entry_64.S:352

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