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

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Message-ID: <20210301164553.GI2696@paulmck-ThinkPad-P72>
Date:   Mon, 1 Mar 2021 08:45:53 -0800
From:   "Paul E. McKenney" <paulmck@...nel.org>
To:     Jürgen Groß <jgross@...e.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        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 Mon, Mar 01, 2021 at 04:53:27PM +0100, Jürgen Groß wrote:
> 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.

Works for me!

							Thanx, Paul