Re: Odroid U3 mutex deadlock.

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Hi Anand,

On 2016-01-02 06:14, Anand Moon wrote:
Hi Krzysztof

On 14 December 2015 at 05:15, Krzysztof Kozlowski
<k.kozlowski@xxxxxxxxxxx> wrote:
On 12.12.2015 13:32, Anand Moon wrote:
Hi Krzysztof,

I am just observing this deadlock om my Odroid U3.
This is not a deadlock yet, just a report from lockdep. Could be a real
issue, could be false positive, maybe some locks miss nesting annotations.

Typical information for bug report would be useful, like the exact
version (it is mentioned in lockdep report but is it really correct?)
and reproducibility. And of course git-bisect would be nice to have, see:
Documentation/BUG-HUNTING

Best regards,
Krzysztof


Thanks for your inputs. I narrowed down to this commit.
----------------------------------------------------------------------------------
commit ec459c0c77faca53cf161830cb264e51bb1abba6
Author: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Date:   Wed Feb 4 23:44:15 2015 +0900

     ARM: dts: add dependency between TV and LCD0 power domains for exynos4

     TV Mixer needs both TV and LCD0 domains enabled to be fully operational.
     This dependency is modelled by making TV power domains a sub-domain of
     LCD0 power domain.

     Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
     Signed-off-by: Kukjin Kim <kgene@xxxxxxxxxx>
-------------------------------------------------------------------------------------
After reverting this I am not observing below lockdep warning report.
But after reverting this patch I observer another bug.

The mentioned lockdep warning is a false positive. Such warning is reported for
every subdomain present in a system. As you noticed that removing dependency
between power domains also removes this warning, but it will introduce real
problems with power on/off sequences of graphics devices.

I will send a patch for genpd core fixing the deplock warning. Thanks for
reporting the issue and pointing a good place to start digging in the source :)

Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland

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