linux-kernel - Re: [RFC PATCH] regulator: Fix recursive mutex lockdep warning

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Message-ID: <55C33E89.2060501@linaro.org>
Date:	Thu, 06 Aug 2015 12:01:29 +0100
From:	Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
To:	Mark Brown <broonie@...nel.org>
CC:	Liam Girdwood <lgirdwood@...il.com>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH] regulator: Fix recursive mutex lockdep warning


On 06/08/15 10:43, Mark Brown wrote:
> On Wed, Aug 05, 2015 at 05:02:08PM +0100, Srinivas Kandagatla wrote:
>> A recursive lockdep warning occurs if you call regulator_set_voltage()
>> on a load switches that are modelled as regulators with a parent supply as
>> there is no nesting annotation for the rdev->mutex.
>> To avoid this warning, use the unlocked version of the get_voltage().
>
> No, just completely removing the locking is broken - the locking is
> there for a reason!  This needs some lockdep dance, either something

Yes, I totally agree, removing locking would have more regressions.

> like what we have for regmaps with a class per regulator or something

lock_class per regulator makes more sense, I will try to cookup an RFC 
patch.
> more fancy but whatever's going on just hacking out locking to shut up
> warnings from lockdep is clearly not a good idea.
>

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