2018-03-13 19:58:11

by SF Markus Elfring

Subject: [PATCH] iio/adc/nau7802: Improve unlocking of a mutex in nau7802_read_raw()

From: Markus Elfring <[email protected]>
Date: Tue, 13 Mar 2018 20:52:26 +0100

* Add a jump target so that a call of the function "mutex_unlock" is stored
only once in this function implementation.

* Replace two calls by goto statements.

This issue was detected by using the Coccinelle software.

Signed-off-by: Markus Elfring <[email protected]>
---
drivers/iio/adc/nau7802.c | 15 +++++----------
1 file changed, 5 insertions(+), 10 deletions(-)

diff --git a/drivers/iio/adc/nau7802.c b/drivers/iio/adc/nau7802.c
index 8997e74a8847..68d06a492760 100644
--- a/drivers/iio/adc/nau7802.c
+++ b/drivers/iio/adc/nau7802.c
@@ -303,10 +303,8 @@ static int nau7802_read_raw(struct iio_dev *indio_dev,
* - Channel 2 is value 1 in the CHS register
*/
ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_CTRL2);
- if (ret < 0) {
- mutex_unlock(&st->lock);
- return ret;
- }
+ if (ret < 0)
+ goto unlock;

if (((ret & NAU7802_CTRL2_CHS_BIT) && !chan->channel) ||
(!(ret & NAU7802_CTRL2_CHS_BIT) &&
@@ -316,18 +314,15 @@ static int nau7802_read_raw(struct iio_dev *indio_dev,
NAU7802_REG_CTRL2,
NAU7802_CTRL2_CHS(chan->channel) |
NAU7802_CTRL2_CRS(st->sample_rate));
-
- if (ret < 0) {
- mutex_unlock(&st->lock);
- return ret;
- }
+ if (ret < 0)
+ goto unlock;
}

if (st->client->irq)
ret = nau7802_read_irq(indio_dev, chan, val);
else
ret = nau7802_read_poll(indio_dev, chan, val);
-
+unlock:
mutex_unlock(&st->lock);
return ret;

--
2.16.2

2018-03-18 10:25:47

by Jonathan Cameron

Subject: Re: [PATCH] iio/adc/nau7802: Improve unlocking of a mutex in nau7802_read_raw()

On Tue, 13 Mar 2018 20:56:25 +0100
SF Markus Elfring <[email protected]> wrote:

> From: Markus Elfring <[email protected]>
> Date: Tue, 13 Mar 2018 20:52:26 +0100
>
> * Add a jump target so that a call of the function "mutex_unlock" is stored
> only once in this function implementation.
>
> * Replace two calls by goto statements.
>
> This issue was detected by using the Coccinelle software.
>
> Signed-off-by: Markus Elfring <[email protected]>
Similar to other cases, this non obvious error handling flow rather implies
that this block of code might work better as a utility function called from
the case statement.

> ---
> drivers/iio/adc/nau7802.c | 15 +++++----------
> 1 file changed, 5 insertions(+), 10 deletions(-)
>
> diff --git a/drivers/iio/adc/nau7802.c b/drivers/iio/adc/nau7802.c
> index 8997e74a8847..68d06a492760 100644
> --- a/drivers/iio/adc/nau7802.c
> +++ b/drivers/iio/adc/nau7802.c
> @@ -303,10 +303,8 @@ static int nau7802_read_raw(struct iio_dev *indio_dev,
> * - Channel 2 is value 1 in the CHS register
> */
> ret = i2c_smbus_read_byte_data(st->client, NAU7802_REG_CTRL2);
> - if (ret < 0) {
> - mutex_unlock(&st->lock);
> - return ret;
> - }
> + if (ret < 0)
> + goto unlock;
>
> if (((ret & NAU7802_CTRL2_CHS_BIT) && !chan->channel) ||
> (!(ret & NAU7802_CTRL2_CHS_BIT) &&
> @@ -316,18 +314,15 @@ static int nau7802_read_raw(struct iio_dev *indio_dev,
> NAU7802_REG_CTRL2,
> NAU7802_CTRL2_CHS(chan->channel) |
> NAU7802_CTRL2_CRS(st->sample_rate));
> -
> - if (ret < 0) {
> - mutex_unlock(&st->lock);
> - return ret;
> - }
> + if (ret < 0)
> + goto unlock;
> }
>
> if (st->client->irq)
> ret = nau7802_read_irq(indio_dev, chan, val);
> else
> ret = nau7802_read_poll(indio_dev, chan, val);
> -
> +unlock:
> mutex_unlock(&st->lock);
blank line before simple returns. It isn't a major enough part to be
worth the noise of adding them to existing code, but there is no reason
to take them out!

> return ret;
>