linux-kernel - [RFC PATCH] extcon: Fix sleeping in atomic context

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Date:	Fri, 26 Sep 2014 13:50:40 +0200
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	MyungJoo Ham <myungjoo.ham@...sung.com>,
	Chanwoo Choi <cw00.choi@...sung.com>,
	Felipe Balbi <balbi@...com>,
	Sangjung Woo <sangjung.woo@...sung.com>,
	Krzysztof Kozlowski <k.kozlowski@...sung.com>,
	linux-kernel@...r.kernel.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Jingoo Han <jg1.han@...sung.com>
Cc:	Kyungmin Park <kyungmin.park@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>
Subject: [RFC PATCH] extcon: Fix sleeping in atomic context

Hi,

When kernel was built with charger manager and extcon, I encountered
a sleep in atomic context after connecting USB cable to the device.

I found this on internal kernel 3.16 on Exynos3250 development board.
Unfortunately I could not reproduce it on mainline kernel because
none of my boards were able to bring up full charging stack
(fuel gauge, charger, charger-manager, extcon).

However, after looking at source code, this should happen also on
mainline kernel.

The fix for bug is simple - use mutexes instead of spin locks. It was
tested on 3.16 but *should* work on mainline.

My questions/request for comments are:
1. Could someone verify this on mainline (test it)?
2. Should I mark it cc-stable? I think yes *but* the patch changes
   few extcon functions from non-sleeping to might_sleep.
   On mainline these affected functions are not used in atomic
   contexts but I am not sure about older stable kernels.
   Applying this to older kernel could lead to another sleep-in-atomic
   issue...

Any comments?

Best regards,
Krzysztof

Krzysztof Kozlowski (1):
  extcon: Fix sleeping in atomic context after connecting USB cable

 drivers/extcon/extcon-class.c | 15 ++++++++-------
 include/linux/extcon.h        |  3 ++-
 2 files changed, 10 insertions(+), 8 deletions(-)

-- 
1.9.1

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