FAILED: patch "[PATCH] iio: imu: inv_mpu6050: fix possible deadlock between mutex" failed to apply to 4.17-stable tree

[<gregkh@linuxfoundation.org>]

The patch below does not apply to the 4.17-stable tree.
If someone wants it applied there, or to any other stable or longterm
tree, then please email the backport, including the original git commit
id to <stable@vger.kernel.org>.

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

>From ca4c8fc97e669d7464a95e006d0ca4eadfa4e4bc Mon Sep 17 00:00:00 2001
From: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Date: Mon, 30 Apr 2018 12:14:09 +0200
Subject: [PATCH] iio: imu: inv_mpu6050: fix possible deadlock between mutex
 and iio

Detected by kernel circular locking dependency checker.

We are locking iio mutex (iio_device_claim_direct_mode) after
locking our internal mutex. But when the buffer starts, iio first
locks its mutex and then we lock our internal one.

To avoid possible deadlock, we need to use the same order
everwhere. So we change the ordering by locking first iio mutex,
then our internal mutex.

Fixes: 68cd6e5b206b ("iio: imu: inv_mpu6050: fix lock issues by using our own mutex")
Cc: stable@vger.kernel.org
Signed-off-by: Jean-Baptiste Maneyrol <jmaneyrol@invensense.com>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>

diff --git a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
index aafa77766b08..7358935fb391 100644
--- a/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
+++ b/drivers/iio/imu/inv_mpu6050/inv_mpu_core.c
@@ -340,12 +340,9 @@ static int inv_mpu6050_read_channel_data(struct iio_dev *indio_dev,
 	int result;
 	int ret;
 
-	result = iio_device_claim_direct_mode(indio_dev);
-	if (result)
-		return result;
 	result = inv_mpu6050_set_power_itg(st, true);
 	if (result)
-		goto error_release;
+		return result;
 
 	switch (chan->type) {
 	case IIO_ANGL_VEL:
@@ -386,14 +383,11 @@ static int inv_mpu6050_read_channel_data(struct iio_dev *indio_dev,
 	result = inv_mpu6050_set_power_itg(st, false);
 	if (result)
 		goto error_power_off;
-	iio_device_release_direct_mode(indio_dev);
 
 	return ret;
 
 error_power_off:
 	inv_mpu6050_set_power_itg(st, false);
-error_release:
-	iio_device_release_direct_mode(indio_dev);
 	return result;
 }
 
@@ -407,9 +401,13 @@ inv_mpu6050_read_raw(struct iio_dev *indio_dev,
 
 	switch (mask) {
 	case IIO_CHAN_INFO_RAW:
+		ret = iio_device_claim_direct_mode(indio_dev);
+		if (ret)
+			return ret;
 		mutex_lock(&st->lock);
 		ret = inv_mpu6050_read_channel_data(indio_dev, chan, val);
 		mutex_unlock(&st->lock);
+		iio_device_release_direct_mode(indio_dev);
 		return ret;
 	case IIO_CHAN_INFO_SCALE:
 		switch (chan->type) {
@@ -532,17 +530,18 @@ static int inv_mpu6050_write_raw(struct iio_dev *indio_dev,
 	struct inv_mpu6050_state  *st = iio_priv(indio_dev);
 	int result;
 
-	mutex_lock(&st->lock);
 	/*
 	 * we should only update scale when the chip is disabled, i.e.
 	 * not running
 	 */
 	result = iio_device_claim_direct_mode(indio_dev);
 	if (result)
-		goto error_write_raw_unlock;
+		return result;
+
+	mutex_lock(&st->lock);
 	result = inv_mpu6050_set_power_itg(st, true);
 	if (result)
-		goto error_write_raw_release;
+		goto error_write_raw_unlock;
 
 	switch (mask) {
 	case IIO_CHAN_INFO_SCALE:
@@ -581,10 +580,9 @@ static int inv_mpu6050_write_raw(struct iio_dev *indio_dev,
 	}
 
 	result |= inv_mpu6050_set_power_itg(st, false);
-error_write_raw_release:
-	iio_device_release_direct_mode(indio_dev);
 error_write_raw_unlock:
 	mutex_unlock(&st->lock);
+	iio_device_release_direct_mode(indio_dev);
 
 	return result;
 }
@@ -643,17 +641,18 @@ inv_mpu6050_fifo_rate_store(struct device *dev, struct device_attribute *attr,
 	    fifo_rate > INV_MPU6050_MAX_FIFO_RATE)
 		return -EINVAL;
 
+	result = iio_device_claim_direct_mode(indio_dev);
+	if (result)
+		return result;
+
 	mutex_lock(&st->lock);
 	if (fifo_rate == st->chip_config.fifo_rate) {
 		result = 0;
 		goto fifo_rate_fail_unlock;
 	}
-	result = iio_device_claim_direct_mode(indio_dev);
-	if (result)
-		goto fifo_rate_fail_unlock;
 	result = inv_mpu6050_set_power_itg(st, true);
 	if (result)
-		goto fifo_rate_fail_release;
+		goto fifo_rate_fail_unlock;
 
 	d = INV_MPU6050_ONE_K_HZ / fifo_rate - 1;
 	result = regmap_write(st->map, st->reg->sample_rate_div, d);
@@ -667,10 +666,9 @@ inv_mpu6050_fifo_rate_store(struct device *dev, struct device_attribute *attr,
 
 fifo_rate_fail_power_off:
 	result |= inv_mpu6050_set_power_itg(st, false);
-fifo_rate_fail_release:
-	iio_device_release_direct_mode(indio_dev);
 fifo_rate_fail_unlock:
 	mutex_unlock(&st->lock);
+	iio_device_release_direct_mode(indio_dev);
 	if (result)
 		return result;