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

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Message-Id: <1217878742.3589.70.camel@twins>
Date:	Mon, 04 Aug 2008 21:39:02 +0200
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
Cc:	Jeremy Fitzhardinge <jeremy@...p.org>,
	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()

On Mon, 2008-08-04 at 12:31 -0700, Linus Torvalds wrote:
> 
> On Mon, 4 Aug 2008, Jeremy Fitzhardinge wrote:
> > 
> > OK.  I don't actually need to do this, but I was asking for completeness.  But
> > to clarify, you only need to do the reverse unlock if you do it after
> > unlocking the outer lock?  If you're still holding the outer lock, you can
> > unlock in any order?
> 
> Release order should always be totally irrelevant, whether you hold outer 
> locks or not. Only the order of _getting_ locks matter.
> 
> And yes, if there is an outer lock, even the order of getting locks is 
> irrelevant, as long as anybody who gets more than one inner lock always 
> holds the outer one.

I agree, its just non-trivial to convince lockdep of this. I can give it
a go though.

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