linux-kernel - Re: MMC/regulator boot hang in -next

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Date:	Mon, 2 Nov 2015 14:27:02 -0800
From:	John Stultz <john.stultz@...aro.org>
To:	Bjorn Andersson <bjorn.andersson@...ymobile.com>
Cc:	Sascha Hauer <s.hauer@...gutronix.de>,
	Ulf Hansson <ulf.hansson@...aro.org>,
	lkml <linux-kernel@...r.kernel.org>,
	Mark Brown <broonie@...nel.org>
Subject: Re: MMC/regulator boot hang in -next

On Mon, Nov 2, 2015 at 2:03 PM, John Stultz <john.stultz@...aro.org> wrote:
> On Mon, Nov 2, 2015 at 12:46 PM, Bjorn Andersson
> <bjorn.andersson@...ymobile.com> wrote:
>> On Mon 02 Nov 11:57 PST 2015, John Stultz wrote:
>>
>>> Trying to move my nexus7 work to -next, I started seeing boot time
>>> hangs. Enabling some debug options provided with a lockdep spew.
>>>
>>> Reverting "regulator: core: Propagate voltage changes to supply
>>> regulators" -  fc42112c0eaa avoids the hang, but I still see lockdep
>>> noise.
>>>
>>> Full log of -next based tree without any reverts follows:
>>
>> It sure does lock like a deadlock to me. Can you figure out which
>> regulator we're talking about here? And confirm that this is 8064 we're
>> talking about
>
> So it looks like we're setting the voltage on lvs1, which then calls
> get_voltage() on s4. At that point the lockdep spew hits.
>
> But as Mark noted *this* spew looks like a false positive, but I
> suspect lockdep is then disabled and can't detect the real hang
> happens shortly afterwards.

Further on this, the lockdep spew happens w/ v4.3 as well. Its just
the deadlock in -next got me to add lockdep in my config.

thanks
-john
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