Re: [PATCH] iio/accel/bmc150: Improve unlocking of a mutex in two functions

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Hi,

On 25-10-17 16:33, SF Markus Elfring wrote:
From: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
Date: Wed, 25 Oct 2017 16:26:29 +0200

Add a jump target so that a call of the function "mutex_unlock" is mostly
stored at the end of these function implementations.
Replace five calls by goto statements.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <elfring@xxxxxxxxxxxxxxxxxxxxx>
---
  drivers/iio/accel/bmc150-accel-core.c | 32 ++++++++++++++------------------
  1 file changed, 14 insertions(+), 18 deletions(-)

diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
index 870f92ef61c2..f2a85a11a5e4 100644
--- a/drivers/iio/accel/bmc150-accel-core.c
+++ b/drivers/iio/accel/bmc150-accel-core.c
@@ -554,18 +554,15 @@ static int bmc150_accel_get_axis(struct bmc150_accel_data *data,
mutex_lock(&data->mutex);
  	ret = bmc150_accel_set_power_state(data, true);
-	if (ret < 0) {
-		mutex_unlock(&data->mutex);
-		return ret;
-	}
+	if (ret < 0)
+		goto unlock_after_failure;
ret = regmap_bulk_read(data->regmap, BMC150_ACCEL_AXIS_TO_REG(axis),
  			       &raw_val, sizeof(raw_val));
  	if (ret < 0) {
  		dev_err(dev, "Error reading axis %d\n", axis);
  		bmc150_accel_set_power_state(data, false);
-		mutex_unlock(&data->mutex);
-		return ret;
+		goto unlock_after_failure;
  	}
  	*val = sign_extend32(le16_to_cpu(raw_val) >> chan->scan_type.shift,
  			     chan->scan_type.realbits - 1);
@@ -575,6 +572,10 @@ static int bmc150_accel_get_axis(struct bmc150_accel_data *data,
  		return ret;
return IIO_VAL_INT;
+
+unlock_after_failure:
+	mutex_unlock(&data->mutex);
+	return ret;
  }
static int bmc150_accel_read_raw(struct iio_dev *indio_dev,

IMHO, if you do this, you should rework the function so that there is a single unlock call
at the end, not a separate one in in error label.

Could e.g. change this:

        ret = bmc150_accel_set_power_state(data, false);
        mutex_unlock(&data->mutex);
        if (ret < 0)
                return ret;

        return IIO_VAL_INT;
}

To:

        ret = bmc150_accel_set_power_state(data, false);
        if (ret < 0)
                goto unlock;

	ret = IIO_VAL_INT;
unlock:
        mutex_unlock(&data->mutex);

        return ret;
}

And also use the unlock label in the other cases, this is actually
quite a normal pattern. I see little use in a patch like this if there
are still 2 unlock paths after the patch.

Regards,

Hans





@@ -1170,28 +1171,23 @@ static int bmc150_accel_trigger_set_state(struct iio_trigger *trig,
  	mutex_lock(&data->mutex);
if (t->enabled == state) {
-		mutex_unlock(&data->mutex);
-		return 0;
+		ret = 0;
+		goto unlock;
  	}
if (t->setup) {
  		ret = t->setup(t, state);
-		if (ret < 0) {
-			mutex_unlock(&data->mutex);
-			return ret;
-		}
+		if (ret < 0)
+			goto unlock;
  	}
ret = bmc150_accel_set_interrupt(data, t->intr, state);
-	if (ret < 0) {
-		mutex_unlock(&data->mutex);
-		return ret;
-	}
+	if (ret < 0)
+		goto unlock;
t->enabled = state;
-
+unlock:
  	mutex_unlock(&data->mutex);
-
  	return ret;
  }
--
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