drivers/power/ds2780_battery.c: fix deadlock upon insertion and removal

Fixes the deadlock when inserting and removing the ds2780.
Signed-off-by: Clifton Barnes <cabarnes@indesign-llc.com>
Cc: Evgeniy Polyakov <zbr@ioremap.net>
Cc: <stable@kernel.org>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

drivers/power/ds2780_battery.c

@@ -39,6 +39,7 @@ struct ds2780_device_info {
 	struct device *dev;
 	struct power_supply bat;
 	struct device *w1_dev;
+	struct task_struct *mutex_holder;
 };
 
 enum current_types {
@@ -63,6 +64,9 @@ static inline struct power_supply *to_power_supply(struct device *dev)
 static inline int ds2780_battery_io(struct ds2780_device_info *dev_info,
 	char *buf, int addr, size_t count, int io)
 {
+	if (dev_info->mutex_holder == current)
+		return w1_ds2780_io_nolock(dev_info->w1_dev, buf, addr, count, io);
+	else
 		return w1_ds2780_io(dev_info->w1_dev, buf, addr, count, io);
 }
 
@@ -775,6 +779,7 @@ static int __devinit ds2780_battery_probe(struct platform_device *pdev)
 	dev_info->bat.properties	= ds2780_battery_props;
 	dev_info->bat.num_properties	= ARRAY_SIZE(ds2780_battery_props);
 	dev_info->bat.get_property	= ds2780_battery_get_property;
+	dev_info->mutex_holder		= current;
 
 	ret = power_supply_register(&pdev->dev, &dev_info->bat);
 	if (ret) {
@@ -804,6 +809,8 @@ static int __devinit ds2780_battery_probe(struct platform_device *pdev)
 		goto fail_remove_bin_file;
 	}
 
+	dev_info->mutex_holder = NULL;
+
 	return 0;
 
 fail_remove_bin_file:
@@ -823,6 +830,8 @@ static int __devexit ds2780_battery_remove(struct platform_device *pdev)
 {
 	struct ds2780_device_info *dev_info = platform_get_drvdata(pdev);
 
+	dev_info->mutex_holder = current;
+
 	/* remove attributes */
 	sysfs_remove_group(&dev_info->bat.dev->kobj, &ds2780_attr_group);