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SubjectRe: [PATCH] Staging: iio: ade7758: Replace mlock with buf_lock
On Sat, 20 Jan 2018 21:14:48 +0530
Shreeya Patel <shreeya.patel23498@gmail.com> wrote:

> iio_dev->mlock is to be used only by the IIO core for protecting
> device mode changes between INDIO_DIRECT and INDIO_BUFFER.
>
> This patch replaces the use of mlock with the already established
> buf_lock mutex.
>
> Signed-off-by: Shreeya Patel <shreeya.patel23498@gmail.com>

You can't do it this simply as it will cause deadlock due to nested
locking of the buf_lock.

To share the lock you will need to provide unlocked versions of
the read and write functions and use those if the lock has already been
taken.

Jonathan

> ---
> drivers/staging/iio/meter/ade7758_core.c | 10 ++++++----
> 1 file changed, 6 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/staging/iio/meter/ade7758_core.c b/drivers/staging/iio/meter/ade7758_core.c
> index 7b7ffe5..1a866cc 100644
> --- a/drivers/staging/iio/meter/ade7758_core.c
> +++ b/drivers/staging/iio/meter/ade7758_core.c
> @@ -523,12 +523,13 @@ static int ade7758_read_raw(struct iio_dev *indio_dev,
> long mask)
> {
> int ret;
> + struct ade7758_state *st = iio_priv(indio_dev);
>
> switch (mask) {
> case IIO_CHAN_INFO_SAMP_FREQ:
> - mutex_lock(&indio_dev->mlock);
> + mutex_lock(&st->buf_lock);
> ret = ade7758_read_samp_freq(&indio_dev->dev, val);
> - mutex_unlock(&indio_dev->mlock);
> + mutex_unlock(&st->buf_lock);
> return ret;
> default:
> return -EINVAL;
> @@ -542,14 +543,15 @@ static int ade7758_write_raw(struct iio_dev *indio_dev,
> int val, int val2, long mask)
> {
> int ret;
> + struct ade7758_state *st = iio_priv(indio_dev);
>
> switch (mask) {
> case IIO_CHAN_INFO_SAMP_FREQ:
> if (val2)
> return -EINVAL;
> - mutex_lock(&indio_dev->mlock);
> + mutex_lock(&st->buf_lock);
> ret = ade7758_write_samp_freq(&indio_dev->dev, val);
> - mutex_unlock(&indio_dev->mlock);
> + mutex_unlock(&st->buf_lock);
> return ret;
> default:
> return -EINVAL;

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