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From: Dmitry Vyukov <dvyukov@google.com>
To: Tetsuo Handa <penguin-kernel@i-love.sakura.ne.jp>
Cc: Peter Zijlstra <peterz@infradead.org>,
	Ingo Molnar <mingo@redhat.com>, Will Deacon <will@kernel.org>,
	Andrew Morton <akpm@linux-foundation.org>,
	LKML <linux-kernel@vger.kernel.org>,
	syzkaller <syzkaller@googlegroups.com>
Subject: Re: [PATCH v2] lockdep: Allow tuning tracing capacity constants.
Date: Wed, 16 Sep 2020 13:28:19 +0200	[thread overview]
Message-ID: <CACT4Y+bjPr=64Lq1-ARD6T=K9LmC_Aor4BRXPcZVtUU8vF0oGg@mail.gmail.com> (raw)
In-Reply-To: <0f7233f7-a04a-e9c9-7920-3a170cc97e4b@i-love.sakura.ne.jp>

On Fri, Sep 4, 2020 at 6:05 PM Tetsuo Handa
<penguin-kernel@i-love.sakura.ne.jp> wrote:
>
> Hello. Can we apply this patch?
>
> This patch addresses top crashers for syzbot, and applying this patch
> will help utilizing syzbot's resource for finding other bugs.

Acked-by: Dmitry Vyukov <dvyukov@google.com>

Peter, do you still have concerns with this?

Both MAX_LOCKDEP_ENTRIES and MAX_LOCKDEP_CHAINS still fire on syzbot a
lot and harm ability to test whole kernel:
https://syzkaller.appspot.com/bug?id=3d97ba93fb3566000c1c59691ea427370d33ea1b
https://syzkaller.appspot.com/bug?id=63fc8d0501c39609dd2f268e4190ec9a72619563

I hate disabling lockdep entirely as it also finds lots of useful things.


> On 2020/08/28 0:20, Tetsuo Handa 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].
> >
> > Let's allow individually tuning upper limits via kernel config options
> > (based on an assumption that there is no inter-dependency among these
> > 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
> >
> > Reported-by: syzbot <syzbot+cd0ec5211ac07c18c049@syzkaller.appspotmail.com>
> > Reported-by: syzbot <syzbot+91fd909b6e62ebe06131@syzkaller.appspotmail.com>
> > Reported-by: syzbot <syzbot+62ebe501c1ce9a91f68c@syzkaller.appspotmail.com>
> > Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
> > ---
> >  kernel/locking/lockdep.c           |  2 +-
> >  kernel/locking/lockdep_internals.h |  8 +++---
> >  lib/Kconfig.debug                  | 40 ++++++++++++++++++++++++++++++
> >  3 files changed, 45 insertions(+), 5 deletions(-)
> >

  reply	other threads:[~2020-09-16 19:08 UTC|newest]

Thread overview: 38+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-25  1:30 [PATCH] lockdep: Introduce CONFIG_LOCKDEP_LARGE Tetsuo Handa
2020-07-25  4:48 ` Dmitry Vyukov
2020-07-25  5:23   ` Tetsuo Handa
2020-08-04  2:36     ` Tetsuo Handa
2020-08-18  9:57       ` Dmitry Vyukov
2020-08-18 11:07         ` Tetsuo Handa
2020-08-18 12:02           ` Dmitry Vyukov
2020-08-18 12:59             ` Tetsuo Handa
2020-08-27 15:20 ` [PATCH v2] lockdep: Allow tuning tracing capacity constants Tetsuo Handa
2020-09-04 16:05   ` Tetsuo Handa
2020-09-16 11:28     ` Dmitry Vyukov [this message]
2020-09-16 11:50       ` peterz
2020-09-16 12:14         ` Dmitry Vyukov
2020-09-28  0:24           ` Tetsuo Handa
2020-09-28  5:12             ` Dmitry Vyukov
2020-10-10 12:58   ` [PATCH v3] " Tetsuo Handa
2020-10-18 13:02     ` Tetsuo Handa
2020-11-18 13:57       ` Tetsuo Handa
2020-11-18 14:23         ` Peter Zijlstra
2020-11-18 14:30           ` Tetsuo Handa
2020-11-18 15:10             ` Peter Zijlstra
2020-11-18 15:31               ` Tetsuo Handa
2020-11-19 12:33                 ` Dmitry Vyukov
2020-11-19 12:43                   ` Dmitry Vyukov
2020-11-19 12:49                     ` Dmitry Vyukov
2020-11-19 13:06                       ` Dmitry Vyukov
2020-11-19 13:45                         ` Tetsuo Handa
2020-11-19 14:05                           ` Dmitry Vyukov
     [not found]                             ` <CACT4Y+aNJmuhk0KicX4FzKW6PhawFBgvrC2gSJcWwUkR8VSSmg@mail.gmail.com>
2020-11-19 14:36                               ` Dmitry Vyukov
2020-11-19 18:08                                 ` Dmitry Vyukov
2020-11-20  9:22                                   ` Dmitry Vyukov
2020-11-20  9:27                                     ` Dmitry Vyukov
2020-11-22  1:56                                       ` Tetsuo Handa
2020-11-27  9:00                                         ` Dmitry Vyukov
2020-12-03 13:47                                           ` Tetsuo Handa
2020-12-04 14:35                                             ` Tetsuo Handa
2020-11-19 14:57                               ` Tetsuo Handa
2021-01-01  8:09     ` [PATCH v4] " Tetsuo Handa

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