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

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Message-ID: <20131202002444.GA22418@teo>
Date:	Sun, 1 Dec 2013 16:24:44 -0800
From:	Anton Vorontsov <anton@...msg.org>
To:	Michael Trimarchi <michael@...rulasolutions.com>
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

On Mon, Dec 02, 2013 at 01:02:40AM +0100, Michael Trimarchi wrote:
> 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?

All kind of bad things might happen, yes. But before that I would expect a
bunch of warnings from might_sleep() stuff.

I would recommend to test the patches using preempt/smp kernels + various
DEBUG_ kernel options set.

Thanks,

Anton
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