From a9f6a19b57c4f37dfd6aa322071948245fecbd91 Mon Sep 17 00:00:00 2001
From: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Date: Tue, 19 May 2015 16:16:29 +0900
Subject: [PATCH] power_supply: Use wrappers to avoid races when registering
 power supply

Use wrappers over get_property() and set_property() internally in power
supply and for sysfs interface. The wrappers provide safe access if
power supply is not yet registered or t is being destroyed.

In case of syfs the theoretical race could happen between ending of
driver's probe and parallel sysfs access:
some_driver_probe()                    userspace
====================================   ===========================
  drv->psy = power_supply_register()
    device_add()
      sysfs entries are created
    atomic_inc(&psy->use_cnt);
                                       store on sysfs attributes
                                         drv->set_property()
                                           dereference of drv->psy
  drv->psy = returned psy;

For leds the race could happen between power supply being destroyed and
ongoing power_supply_changed_work().

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@samsung.com>
Signed-off-by: Sebastian Reichel <sre@kernel.org>
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