[syzbot] BUG: MAX_LOCKDEP_KEYS too low! (2)

Tetsuo Handa penguin-kernel at i-love.sakura.ne.jp
Thu May 20 05:02:00 UTC 2021

On 2021/05/20 5:09, Dmitry Vyukov wrote:
> On Wed, May 19, 2021 at 9:58 PM Randy Dunlap <rdunlap at infradead.org> wrote:
>> On 5/19/21 12:48 PM, Dmitry Vyukov wrote:
>>> On Wed, May 19, 2021 at 7:35 PM syzbot
>>> <syzbot+a70a6358abd2c3f9550f at syzkaller.appspotmail.com> wrote:
>>>> Hello,
>>>> syzbot found the following issue on:
>>>> HEAD commit:    b81ac784 net: cdc_eem: fix URL to CDC EEM 1.0 spec
>>>> git tree:       net
>>>> console output: https://syzkaller.appspot.com/x/log.txt?x=15a257c3d00000
>>>> kernel config:  https://syzkaller.appspot.com/x/.config?x=5b86a12e0d1933b5
>>>> dashboard link: https://syzkaller.appspot.com/bug?extid=a70a6358abd2c3f9550f
>>>> Unfortunately, I don't have any reproducer for this issue yet.
>>>> IMPORTANT: if you fix the issue, please add the following tag to the commit:
>>>> Reported-by: syzbot+a70a6358abd2c3f9550f at syzkaller.appspotmail.com
>>>> BUG: MAX_LOCKDEP_KEYS too low!
>> include/linux/lockdep.h
>> #define MAX_LOCKDEP_KEYS_BITS           13
>> #define MAX_LOCKDEP_KEYS                (1UL << MAX_LOCKDEP_KEYS_BITS)
> Ouch, so it's not configurable yet :(

I didn't try to make this value configurable, for

> Unless, of course, we identify the offender that produced thousands of
> lock classes in the log and fix it.

number of currently active locks should decrease over time.
If this message is printed, increasing this value unlikely helps.

We have https://lkml.kernel.org/r/c099ad52-0c2c-b886-bae2-c64bd8626452@ozlabs.ru
which seems to be unresolved.

Regarding this report, cleanup of bonding device is too slow to catch up to
creation of bonding device?

We might need to throttle creation of BPF, bonding etc. which involve WQ operation for clean up ?

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