linux-kernel - Re: irq lock inversion

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Date:	Mon, 9 Nov 2009 16:34:18 +0100
From:	Jens Axboe <jens.axboe@...cle.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	Tejun Heo <tj@...nel.org>, Jiri Kosina <jkosina@...e.cz>,
	Peter Zijlstra <peterz@...radead.org>,
	Yinghai Lu <yhlu.kernel@...il.com>,
	Thomas Gleixner <tglx@...utronix.de>, cl@...ux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: irq lock inversion

On Sun, Nov 08 2009, Ingo Molnar wrote:
> 
> * Jens Axboe <jens.axboe@...cle.com> wrote:
> 
> > On Fri, Nov 06 2009, Ingo Molnar wrote:
> > > Read the lockdep message please, consider all the backtraces it prints, 
> > > it says something different.
> > 
> > In all honesty, reading and parsing lockdep messages requires a 
> > special state of mind. IOW, readability is not its high point.
> 
> We frequently do patches to improve the messages but there's a hard 
> limit: generally the messages mirror the complexity of the underlying 
> locking scenario.
> 
> Unfortunately lockdep cannot pretend something is simple when it is not. 
> There are two ways out of that: either to simplify the underlying 
> locking rules, or to understand them.

I think the primary problem is that it tries to condense too much
information, instead of just spelling it out. That may be obvious to a
person intimately familiar with lockdep, but not to others. Things like
the STATE line, for instance. It would read a lot easier if these things
were just spelled out.

I know this message isn't really productive, just tossing it out there.
I'll try to to back it up with a patch the next time it annoys me :-)

-- 
Jens Axboe

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