linux-kernel - Re: [PATCH v5] lockdep: Allow tuning tracing capacity constants.

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Message-ID: <968067e3-d87b-b04d-c2ba-fad04c439130@i-love.sakura.ne.jp>
Date:   Mon, 5 Apr 2021 20:44:58 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [PATCH v5] lockdep: Allow tuning tracing capacity constants.

Dmitry, I've just sent this patch to tomoyo-test1.git tree, for finding bugs
(which previously could not be found due to lack of this patch) in linux-next.git
will be helpful anyway.

Since this patch should appear in tomorrow's linux-next.git , please prepare
syzkaller for tuning appropriate values (default value + 1 should be OK).

On 2021/03/31 19:58, Tetsuo Handa wrote:
> Peter, are you there?
> 
> If you keep silence, we will assume that applying this patch is the way to go.
> 
> On 2021/03/20 16:34, Dmitry Vyukov wrote:
>> On Mon, Feb 8, 2021 at 11:29 AM Tetsuo Handa
>> <penguin-kernel@...ove.sakura.ne.jp> wrote:
>>>
>>> Since syzkaller continues various test cases until the kernel crashes,
>>> syzkaller tends to examine more locking dependencies than normal systems.
>>> As a result, syzbot is reporting that the fuzz testing was terminated
>>> due to hitting upper limits lockdep can track [1] [2] [3]. Since analysis
>>> via /proc/lockdep* did not show any obvious culprit [4] [5], we have no
>>> choice but allow tuning tracing capacity constants.
>>>
>>> [1] https://syzkaller.appspot.com/bug?id=3d97ba93fb3566000c1c59691ea427370d33ea1b
>>> [2] https://syzkaller.appspot.com/bug?id=381cb436fe60dc03d7fd2a092b46d7f09542a72a
>>> [3] https://syzkaller.appspot.com/bug?id=a588183ac34c1437fc0785e8f220e88282e5a29f
>>> [4] https://lkml.kernel.org/r/4b8f7a57-fa20-47bd-48a0-ae35d860f233@i-love.sakura.ne.jp
>>> [5] https://lkml.kernel.org/r/1c351187-253b-2d49-acaf-4563c63ae7d2@i-love.sakura.ne.jp
>>>
>>> Reported-by: syzbot <syzbot+cd0ec5211ac07c18c049@...kaller.appspotmail.com>
>>> Reported-by: syzbot <syzbot+91fd909b6e62ebe06131@...kaller.appspotmail.com>
>>> Reported-by: syzbot <syzbot+62ebe501c1ce9a91f68c@...kaller.appspotmail.com>
>>> References: https://lkml.kernel.org/r/1595640639-9310-1-git-send-email-penguin-kernel@I-love.SAKURA.ne.jp
>>> Signed-off-by: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
>>> Acked-by: Dmitry Vyukov <dvyukov@...gle.com>
>>
>> Peter, ping.
>> Please at least provide some feedback.
>> This is still the top crasher on syzbot and harms testing of the whole
>> kernel. I am periodically thinking of disabling LOCKDEP on syzbot as
>> harming more than helping, but so far talking myself out of it because
>> it will likely be broken more when we try to re-enable it and I still
>> hope for a timely resolution of this issue.
>>
>