linux-kernel - Re: [RFC PATCH 1/2] regmap: add configurable lock class key for lockdep

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Message-ID: <20150625153325.GR14071@sirena.org.uk>
Date:	Thu, 25 Jun 2015 16:33:25 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Lars-Peter Clausen <lars@...afoo.de>
Cc:	Arjan van de Ven <arjan@...ux.intel.com>,
	Nicolas Boichat <drinkcat@...omium.org>,
	Mauro Carvalho Chehab <mchehab@....samsung.com>,
	Antti Palosaari <crope@....fi>, Ingo Molnar <mingo@...hat.com>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	linux-kernel@...r.kernel.org, Bard Liao <bardliao@...ltek.com>,
	Oder Chiou <oder_chiou@...ltek.com>,
	Liam Girdwood <lgirdwood@...il.com>,
	Jaroslav Kysela <perex@...ex.cz>, Takashi Iwai <tiwai@...e.de>,
	alsa-devel@...a-project.org,
	Anatol Pomozov <anatol.pomozov@...il.com>
Subject: Re: [RFC PATCH 1/2] regmap: add configurable lock class key for
 lockdep

On Thu, Jun 25, 2015 at 05:03:00PM +0200, Lars-Peter Clausen wrote:
> On 06/25/2015 03:21 PM, Arjan van de Ven wrote:

> >wouldn't it be better to use the mutex_lock_nested() and co to explicitly
> >express your hierarchy?

> That would require that the hierarchy is known in advance. The hierarchy
> depends on the hardware topology. Different systems will have different
> hierarchies where the relationship between locks can change and it will be
> hard to find a hierarchy that works across all topologies.

It depends on what you use as the key for the nested locking stuff.  If
you assign a key per regmap (casting the pointer to an integer, using an
IDR or something).  I don't know if that creates problems for the
locking code, I'd not expect so but then I'd not have expected the
problem in the first place.

As far as I can tell we're likely to end up needing a key per regmap or
something similar.

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