linux-kernel - Re: [PATCH] gpiolib: irqchip: use different lockdep class for each gpio irqchip

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Date:	Fri, 14 Aug 2015 16:05:52 +0300
From:	Grygorii Strashko <grygorii.strashko@...com>
To:	Lars-Peter Clausen <lars@...afoo.de>,
	Linus Walleij <linus.walleij@...aro.org>
CC:	Alexandre Courbot <gnurou@...il.com>,
	Linux-OMAP <linux-omap@...r.kernel.org>,
	"linux-gpio@...r.kernel.org" <linux-gpio@...r.kernel.org>,
	Sekhar Nori <nsekhar@...com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Geert Uytterhoeven <geert@...ux-m68k.org>,
	Roger Quadros <rogerq@...com>
Subject: Re: [PATCH] gpiolib: irqchip: use different lockdep class for each
 gpio irqchip

On 08/14/2015 03:40 PM, Lars-Peter Clausen wrote:
> On 08/14/2015 02:34 PM, Linus Walleij wrote:
> [...]
>> Every chip will get their own lock class on the heap.
>>
>> But I think it is a bit kludgy.
>>
>> Is it not possible to have  the lock key in struct gpio_chip
>> be a real member instead of a pointer and get a per-chip
>> lock that way?
>>
>> (...)
>> struct lock_class_key lock_key;
>>
>> instead of:
>>
>> struct lock_class_key  *lock_key;
>>
>> -> problem solved, without kludgy header defines?
> 
> 
> Lock keys need to be in persistent memory since they have a unlimited life
> time. Once registered it is expected to exist until the system is reset.
> 
> We recently fixed the same issue of nested locks in regmap. For reference
> the discussion with had a look at different ways to solve this can be found
> here[1] and the final patch series that went in here[2].
> 
> - Lars
> 
> [1] https://lkml.org/lkml/2015/6/25/144
> [2] https://lkml.org/lkml/2015/7/8/43

I've actually followed [2], but without deep digging in Lock keys anatomy :)
(as mentioned in commit message)

-- 
regards,
-grygorii
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