Message-Id: <56315101-B3A5-4596-947E-5D34A5FFBB37@gmx.de>
Date:   Sat, 5 Mar 2022 16:12:27 +0100
From:   Reimar Döffinger <Reimar.Doeffinger@....de>
To:     Byungchul Park <byungchul.park@....com>
Cc:     Theodore Ts'o <tytso@....edu>, damien.lemoal@...nsource.wdc.com,
        linux-ide@...r.kernel.org, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, torvalds@...ux-foundation.org,
        mingo@...hat.com, linux-kernel@...r.kernel.org,
        peterz@...radead.org, will@...nel.org, tglx@...utronix.de,
        rostedt@...dmis.org, joel@...lfernandes.org, sashal@...nel.org,
        daniel.vetter@...ll.ch, chris@...is-wilson.co.uk,
        duyuyang@...il.com, johannes.berg@...el.com, tj@...nel.org,
        willy@...radead.org, david@...morbit.com, amir73il@...il.com,
        bfields@...ldses.org, gregkh@...uxfoundation.org,
        kernel-team@....com, linux-mm@...ck.org, akpm@...ux-foundation.org,
        mhocko@...nel.org, minchan@...nel.org, hannes@...xchg.org,
        vdavydov.dev@...il.com, sj@...nel.org, jglisse@...hat.com,
        dennis@...nel.org, cl@...ux.com, penberg@...nel.org,
        rientjes@...gle.com, vbabka@...e.cz, ngupta@...are.org,
        linux-block@...r.kernel.org, paolo.valente@...aro.org,
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        jlayton@...nel.org, dan.j.williams@...el.com, hch@...radead.org,
        djwong@...nel.org, dri-devel@...ts.freedesktop.org,
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        melissa.srw@...il.com, hamohammed.sa@...il.com
Subject: Re: Report 2 in ext4 and journal based on v5.17-rc1

Hi,
Sorry to butt in as an outsider, but this seems like a shockingly disrespectful discussion for such a wide CC list.
I don't want to make rules how you discuss things (I very rarely contribute), and I see the value in a frank discussion, but maybe you could continue with a reduced CC list?
I find it unlikely that I am the only one who could do without this.

Best regards,
Reimar Döffinger

> On 5 Mar 2022, at 15:55, Byungchul Park <byungchul.park@....com> wrote:
> 
> On Fri, Mar 04, 2022 at 10:40:35PM -0500, Theodore Ts'o wrote:
>> On Fri, Mar 04, 2022 at 12:20:02PM +0900, Byungchul Park wrote:
>>> 
>>> I found a point that the two wait channels don't lead a deadlock in
>>> some cases thanks to Jan Kara. I will fix it so that Dept won't
>>> complain it.
>> 
>> I sent my last (admittedly cranky) message before you sent this.  I'm
>> glad you finally understood Jan's explanation.  I was trying to tell
> 
> Not finally. I've understood him whenever he tried to tell me something.
> 
>> you the same thing, but apparently I failed to communicate in a
> 
> I don't think so. Your point and Jan's point are different. All he has
> said make sense. But yours does not.
> 
>> sufficiently clear manner.  In any case, what Jan described is a
>> fundamental part of how wait queues work, and I'm kind of amazed that
>> you were able to implement DEPT without understanding it.  (But maybe
> 
> Of course, it was possible because all that Dept has to know for basic
> work is wait and event. The subtle things like what Jan told me help
> Dept be better.
> 
>> that is why some of the DEPT reports were completely incomprehensible
> 
> It's because you are blinded to blame at it without understanding how
> Dept works at all. I will fix those that must be fixed. Don't worry.
> 
>> to me; I couldn't interpret why in the world DEPT was saying there was
>> a problem.)
> 
> I can tell you if you really want to understand why. But I can't if you
> are like this.
> 
>> In any case, the thing I would ask is a little humility.  We regularly
>> use lockdep, and we run a huge number of stress tests, throughout each
>> development cycle.
> 
> Sure.
> 
>> So if DEPT is issuing lots of reports about apparently circular
>> dependencies, please try to be open to the thought that the fault is
> 
> No one was convinced that Dept doesn't have a fault. I think your
> worries are too much.
> 
>> in DEPT, and don't try to argue with maintainers that their code MUST
>> be buggy --- but since you don't understand our code, and DEPT must be
> 
> No one argued that their code must be buggy, either. So I don't think
> you have to worry about what's never happened.
> 
>> theoretically perfect, that it is up to the Maintainers to prove to
>> you that their code is correct.
>> 
>> I am going to gently suggest that it is at least as likely, if not
>> more likely, that the failure is in DEPT or your understanding of what
> 
> No doubt. I already think so. But it doesn't mean that I have to keep
> quiet without discussing to imporve Dept. I will keep improving Dept in
> a reasonable way.
> 
>> how kernel wait channels and locking works.  After all, why would it
>> be that we haven't found these problems via our other QA practices?
> 
> Let's talk more once you understand how Dept works at least 10%. Or I
> think we cannot talk in a productive way.
> 

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