linux-kernel - Re: [PATCH v3 05/18] regulator: core: Reduce critical area in _regulator

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Message-ID: <20150807120752.GQ20873@sirena.org.uk>
Date:	Fri, 7 Aug 2015 13:07:52 +0100
From:	Mark Brown <broonie@...nel.org>
To:	Tomeu Vizoso <tomeu.vizoso@...labora.com>
Cc:	linux-kernel@...r.kernel.org, Rob Herring <robh+dt@...nel.org>,
	Stephen Warren <swarren@...dotorg.org>,
	Javier Martinez Canillas <javier@....samsung.com>,
	Thierry Reding <thierry.reding@...il.com>,
	"Rafael J. Wysocki" <rjw@...ysocki.net>,
	linux-arm-kernel@...ts.infradead.org,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	devicetree@...r.kernel.org,
	Linus Walleij <linus.walleij@...aro.org>,
	linux-acpi@...r.kernel.org, Arnd Bergmann <arnd@...db.de>
Subject: Re: [PATCH v3 05/18] regulator: core: Reduce critical area in
 _regulator_get

On Thu, Aug 06, 2015 at 04:11:42PM +0200, Tomeu Vizoso wrote:

> This backtrace illustrates the situation described above:
> 
> (regulator_register) from [<c05efe64>]
> (devm_regulator_register+0x48/0x84)

Please don't paste entire backtraces into commit messages, they are
enormous and contain very little useful content - they just obscure
actual information in the commit message.  If you feel there's useful
information in there just include edited highlights with only that.

> +static int _regulator_enable(struct regulator *regulator, bool do_lock)
>  {
> -	int ret;
> +	struct regulator_dev *rdev = regulator->rdev;
> +	int ret = 0;
>  
> -	lockdep_assert_held_once(&rdev->mutex);
> +	if (regulator->always_on)
> +		return 0;
> +
> +	if (rdev->supply) {
> +		ret = regulator_enable(rdev->supply);
> +		if (ret != 0)
> +			return ret;
> +	}
> +
> +	if (do_lock)
> +		mutex_lock(&rdev->mutex);
> +	else
> +		lockdep_assert_held_once(&rdev->mutex);

Eew.  This do_lock stuff is *not* nice and going to be fragile.  I'm not
a fan, we need something better.

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