linux-kernel - Re: [PATCH 3/3] kernel/smp: add more data to CSD lock debugging

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Date:   Mon, 1 Mar 2021 16:53:27 +0100
From:   Jürgen Groß <jgross@...e.com>
To:     Peter Zijlstra <peterz@...radead.org>,
        "Paul E. McKenney" <paulmck@...nel.org>
Cc:     linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org,
        mhocko@...e.com, Jonathan Corbet <corbet@....net>
Subject: Re: [PATCH 3/3] kernel/smp: add more data to CSD lock debugging

On 01.03.21 16:45, Peter Zijlstra wrote:
> On Sun, Feb 28, 2021 at 04:07:04PM -0800, Paul E. McKenney wrote:
>> On Fri, Feb 26, 2021 at 10:05:51PM +0100, Peter Zijlstra wrote:
>>> On Fri, Feb 26, 2021 at 10:12:05AM -0800, Paul E. McKenney wrote:
>>>> On Fri, Feb 26, 2021 at 05:38:44PM +0100, Peter Zijlstra wrote:
>>>>>
>>>>> I hate all of this, but if this will finally catch the actual problem,
>>>>> we can then revert all this, so sure.
>>>>
>>>> OK, I will bite...  What exactly do you hate about it?
>>>
>>> It's ugly and messy. We're basically commiting a debug session. Normally
>>> gunk like this is done in private trees, then we find the problem and
>>> fix that and crap like this never sees the light of day.
>>
>> Is your hatred due to the presence of debug code at all, or a belief that
>> this code is unlikely to be useful in any subsequent IPI-related bug hunt?
> 
> The clutter, mostly I think. There's a lot of debug sprinkled about.

I agree.

In case we are able to identify the root cause of the problem I think
it would be no problem to revert this patch and put a comment into smp.c
naming the commit-id of this patch and what it was good for. This will
enable future bug hunters to make use of the patch without spoiling the
code for others.


Juergen


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