linux-kernel - Re: [PATCH v3] lockdep: Allow tuning tracing capacity constants.

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Message-ID: <5e8342c4-702f-80a9-e669-8a7386ce0da1@i-love.sakura.ne.jp>
Date:   Thu, 19 Nov 2020 22:45:25 +0900
From:   Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
To:     Dmitry Vyukov <dvyukov@...gle.com>
Cc:     syzkaller <syzkaller@...glegroups.com>,
        Ingo Molnar <mingo@...hat.com>, Will Deacon <will@...nel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Peter Zijlstra <peterz@...radead.org>
Subject: Re: [PATCH v3] lockdep: Allow tuning tracing capacity constants.

On 2020/11/19 22:06, Dmitry Vyukov wrote:
>>>>
>>>> I am trying to reproduce this locally first. syzbot caims it can
>>>> reproduce it with a number of very simpler reproducers (like spawn
>>>> process, unshare, create socket):
>>>> https://syzkaller.appspot.com/bug?id=8a18efe79140782a88dcd098808d6ab20ed740cc
>>>>
>>>> I see a very slow drift, but it's very slow, so get only to:
>>>>  direct dependencies:                 22072 [max: 32768]
>>>>
>>>> But that's running a very uniform workload.
>>>>
>>>> However when I tried to cat /proc/lockdep to see if there is anything
>>>> fishy already,
>>>> I got this (on c2e7554e1b85935d962127efa3c2a76483b0b3b6).
>>>>
>>>> Some missing locks?

Not a TOMOYO's bug. Maybe a lockdep's bug.

> 
> But I don't know if it's enough to explain the overflow or not...
> 

Since you can't hit the limit locally, I guess we need to ask syzbot to
run massive testcases.