From: Antti Palosaari <crope@iki.fi>
To: Mark Brown <broonie@kernel.org>
Cc: linux-media@vger.kernel.org, Lars-Peter Clausen <lars@metafoo.de>
Subject: Re: [PATCHv2 1/2] regmap: add configurable lock class key for lockdep
Date: Mon, 22 Dec 2014 15:53:10 +0200 [thread overview]
Message-ID: <54982246.20300@iki.fi> (raw)
In-Reply-To: <20141222133142.GM17800@sirena.org.uk>
On 12/22/2014 03:31 PM, Mark Brown wrote:
> On Mon, Dec 22, 2014 at 02:55:23PM +0200, Antti Palosaari wrote:
>> On 12/22/2014 02:44 PM, Mark Brown wrote:
>>> On Sun, Dec 21, 2014 at 12:34:51AM +0200, Antti Palosaari wrote:
>
>>>> I2C client and I2C adapter are using regmap. As a solution, add
>>>> configuration option to pass custom lock class key for lockdep
>>>> validator.
>
>>> Why is this configurable, how would a device know if the system it is in
>>> needs a custom locking class and can safely use one?
>
>> If RegMap instance is bus master, eg. I2C adapter, then you should define
>> own custom key. If you don't define own key and there will be slave on that
>> bus which uses RegMap too, there will be recursive locking from a lockdep
>> point of view.
>
> That doesn't really explain to me why this is configurable, why should
> drivers have to worry about this?
Did you read the lockdep documentation I pointed previous mail?
from: Documentation/locking/lockdep-design.txt
There is not very detailed documentation available, but the section
"Exception: Nested data dependencies leading to nested locking" explains
something.
One possibility is to disable lockdep checking from that driver totally,
then drivers do not need to care it about. But I don't think it is
proper way. One solution is to use custom regmap locking available
already, but Mauro nor me didn't like that hack:
[RFC HACK] rtl2832: implement own lock for RegMap
https://www.mail-archive.com/linux-media@vger.kernel.org/msg83323.html
> Please also write technical terms like regmap normally.
Lower-case letters?
regards
Antti
--
http://palosaari.fi/
next prev parent reply other threads:[~2014-12-22 13:53 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-12-20 22:34 [PATCHv2 1/2] regmap: add configurable lock class key for lockdep Antti Palosaari
2014-12-20 22:34 ` [PATCHv2 2/2] rtl2832: use custom lock class key for regmap Antti Palosaari
2014-12-22 12:44 ` [PATCHv2 1/2] regmap: add configurable lock class key for lockdep Mark Brown
2014-12-22 12:55 ` Antti Palosaari
2014-12-22 13:31 ` Mark Brown
2014-12-22 13:53 ` Antti Palosaari [this message]
2014-12-22 15:05 ` Mark Brown
2015-02-02 14:31 ` Mauro Carvalho Chehab
2015-02-03 12:06 ` Mark Brown
2014-12-22 14:23 ` Mauro Carvalho Chehab
2014-12-22 15:32 ` Mark Brown
2014-12-22 20:06 ` Mark Brown
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