linux-kernel - Re: [RFC][PATCH 7/7] lockdep: spin_lock_nest

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Message-ID: <48ECE5A4.1040003@redhat.com>
Date:	Wed, 08 Oct 2008 12:53:56 -0400
From:	Steven Rostedt <srostedt@...hat.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Steven Rostedt <rostedt@...dmis.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	David Miller <davem@...emloft.net>, hugh@...itas.com,
	mingo@...e.hu, akpm@...ux-foundation.org,
	linux-kernel@...r.kernel.org, davej@...hat.com
Subject: Re: [RFC][PATCH 7/7] lockdep: spin_lock_nest_lock()

Linus Torvalds wrote:
>
>   
> I know for a fact that some people thought unlocking in non-nested order 
> was a bug. And I believe that belief is a dangerous one.
>   

Ah, OK. You are fighting against nesting nazis, fair enough.

I have written a bit of code where nesting was not possible (similar to
your example, but I call those traversal locking not nesting). I just 
find that
the locks should be nested when the nesting is natural. Breaking the nesting
on natural nesting locks is a bug, IMHO.  But as you know, there are several
programmers out there that can not determine the difference between natural
nesting locks and non nesting locks.

By adding such a rule, those that can not tell the difference will be 
making a
lot of needless noise, hence, it is best not to make any such rule.

Lesson learned.  I'll now go back to debugging my code.

-- Steve

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