linux-kernel - Re: [PATCH] staging: ad7759: Replace mlock with driver private lock

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Date:   Wed, 22 Mar 2017 20:33:00 +0000
From:   Jonathan Cameron <jic23@...nel.org>
To:     Arushi Singhal <arushisinghal19971997@...il.com>, lars@...afoo.de
Cc:     Michael Hennerich <Michael.Hennerich@...log.com>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-iio@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, outreachy-kernel@...glegroups.com
Subject: Re: [PATCH] staging: ad7759: Replace mlock with driver private lock

On 20/03/17 16:09, Arushi Singhal wrote:
> The IIO subsystem is redefining iio_dev->mlock to be used by
> the IIO core only for protecting device operating mode changes.
> ie. Changes between INDIO_DIRECT_MODE, INDIO_BUFFER_* modes.
> 
> In this driver, mlock was being used to protect hardware state
> changes.  Replace it with a lock in the devices global data.
> 
> Signed-off-by: Arushi Singhal <arushisinghal19971997@...il.com>
> ---
>  drivers/staging/iio/meter/ade7759.c | 4 ++--
>  drivers/staging/iio/meter/ade7759.h | 1 +
>  2 files changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/staging/iio/meter/ade7759.c b/drivers/staging/iio/meter/ade7759.c
> index 944ee3401029..1d1e0b33021f 100644
> --- a/drivers/staging/iio/meter/ade7759.c
> +++ b/drivers/staging/iio/meter/ade7759.c
> @@ -381,7 +381,7 @@ static ssize_t ade7759_write_frequency(struct device *dev,
>  	if (!val)
>  		return -EINVAL;
>  
> -	mutex_lock(&indio_dev->mlock);
> +	mutex_lock(&st->buf_lock);
>  
>  	t = 27900 / val;
>  	if (t > 0)
> @@ -402,7 +402,7 @@ static ssize_t ade7759_write_frequency(struct device *dev,
Deadlock as this call also take the buf_lock mutex..


>  	ret = ade7759_spi_write_reg_16(dev, ADE7759_MODE, reg);
>  
>  out:
> -	mutex_unlock(&indio_dev->mlock);
> +	mutex_unlock(&st->buf_lock);
>  
>  	return ret ? ret : len;
>  }
> diff --git a/drivers/staging/iio/meter/ade7759.h b/drivers/staging/iio/meter/ade7759.h
> index f0716d2fdf8e..4f69bb93cc45 100644
> --- a/drivers/staging/iio/meter/ade7759.h
> +++ b/drivers/staging/iio/meter/ade7759.h
> @@ -42,6 +42,7 @@
>   * @buf_lock:		mutex to protect tx and rx
>   * @tx:			transmit buffer
>   * @rx:			receive buffer
> + * @lock		protect sensor state
?
>   **/
>  struct ade7759_state {
>  	struct spi_device	*us;
>