linux-kernel - Re: [PATCH v2 2/3] bq2415x_charger: Use power

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Message-ID: <CAOf5uwnkQwkS7_fsLtC5nzdXyS1Rzw2SkxaziUuJrO9SKXh3yw@mail.gmail.com>
Date:	Mon, 2 Dec 2013 01:02:40 +0100
From:	Michael Trimarchi <michael@...rulasolutions.com>
To:	Anton Vorontsov <anton@...msg.org>
Cc:	Pali Rohár <pali.rohar@...il.com>,
	David Woodhouse <dwmw2@...radead.org>,
	Tony Lindgren <tony@...mide.com>,
	Russell King <linux@....linux.org.uk>,
	linux-kernel@...r.kernel.org,
	Linux OMAP Mailing List <linux-omap@...r.kernel.org>,
	freemangordon@....bg, aaro.koskinen@....fi, pavel@....cz
Subject: Re: [PATCH v2 2/3] bq2415x_charger: Use power_supply notifier for automode

Hi Anton

On Sun, Dec 1, 2013 at 11:37 PM, Anton Vorontsov <anton@...msg.org> wrote:
> On Mon, Nov 25, 2013 at 08:16:34PM +0100, Michael Trimarchi wrote:
> ...
>> >> So you can read this value without any type of synchronization
>> >> with the power_supply_core
>> >> and sysfs implementation?
> ...
>> https://lists.ubuntu.com/archives/kernel-team/2013-January/025206.html
>>
>> I found and equivalent scenario that I was trying to said
>
> That's a good question, actually. Even though in Pali's case the notifier
> is atomic (so that we are pretty confident that the object won't be
> unregistered), there is still a possiblity of a dead lock, for example. So

So if the get_property is a sleeping function it will be a deadlock. Right?

Michael

> notifiers should be careful to not hold any locks, because the other
> driver might call get_property(), which might acquire locks.
>
> Thanks,
>
> Anton
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