linux-kernel - Re: [PATCH] lockdep: Show up to three levels for a deadlock scenario

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Date:   Tue, 19 Dec 2017 12:10:10 -0500
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Dhaval Giani <dhaval.giani@...cle.com>
Cc:     Peter Zijlstra <peterz@...radead.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH] lockdep: Show up to three levels for a deadlock
 scenario

On Tue, 19 Dec 2017 11:54:10 -0500
Dhaval Giani <dhaval.giani@...cle.com> wrote:

> On 2017-12-19 11:52 AM, Steven Rostedt wrote:
> > On Tue, 19 Dec 2017 17:46:19 +0100
> > Peter Zijlstra <peterz@...radead.org> wrote:
> > 
> >   
> >> It really isn't that hard, Its mostly a question of TL;DR.
> >>
> >> #0 is useless and should be thrown out
> >> #1 shows where we take #1 while holding #0
> >> ..
> >> #n shows where we take #n while holding #n-1
> >>
> >> And the bottom callstack shows where we take #0 while holding #n. Which
> >> gets you a nice circle in your graph, which spells deadlock.
> >>
> >> Plenty people have shown they get this stuff.  
> > 
> > 
> > Then I suggest that you can either take my patch to improve the
> > visual or remove the visual completely, as nobody cares about it.
> >   
> 
> I prefer the former. As Steven has mentioned elsewhere, people find
> lockdep output hard to follow (enough that he has given talks :) )
> 

Not to mention. There's commit logs that throw everything out except
for this information. See commits:

 692b48258dda
 5acb3cc2c2e9
 7b7622bb95eb5
 478fe3037b227
 fdaf0a51bad49
 1ddd45f8d76f0
 63aea0dbab90a
 1215e51edad12
 f159b3c7cd45c

And those only go back to March of this year.

-- Steve