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SubjectRe: [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@users.sourceforge.net>
> 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@users.sourceforge.net>
> ---
> 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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