linux-kernel - Re: [PATCH] staging: iio: ad7152: Fix deadlock in ad7152_write_raw_samp

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Message-ID: <38c5952c-8c92-9d97-73cd-06fd0d74aaf3@metafoo.de>
Date:   Sun, 28 May 2017 11:47:04 +0200
From:   Lars-Peter Clausen <lars@...afoo.de>
To:     Alexey Khoroshilov <khoroshilov@...ras.ru>,
        Michael Hennerich <Michael.Hennerich@...log.com>,
        Jonathan Cameron <jic23@...nel.org>,
        Hartmut Knaack <knaack.h@....de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     linux-iio@...r.kernel.org, devel@...verdev.osuosl.org,
        linux-kernel@...r.kernel.org, ldv-project@...uxtesting.org
Subject: Re: [PATCH] staging: iio: ad7152: Fix deadlock in
 ad7152_write_raw_samp_freq()

On 05/27/2017 12:53 AM, Alexey Khoroshilov wrote:
> ad7152_write_raw_samp_freq() is called by ad7152_write_raw() with
> chip->state_lock held. So, there is unavoidable deadlock when
> ad7152_write_raw_samp_freq() locks the mutex itself.
> 
> The patch removes unneeded locking.
> 
> Found by Linux Driver Verification project (linuxtesting.org).
> 
> Signed-off-by: Alexey Khoroshilov <khoroshilov@...ras.ru>

Looks good, thanks.

Fixes: 6572389bcc11 ("staging: iio: cdc: ad7152: Implement
IIO_CHAN_INFO_SAMP_FREQ attribute")
Acked-by: Lars-Peter Clausen <lars@...afoo.de>


> ---
>  drivers/staging/iio/cdc/ad7152.c | 6 +-----
>  1 file changed, 1 insertion(+), 5 deletions(-)
> 
> diff --git a/drivers/staging/iio/cdc/ad7152.c b/drivers/staging/iio/cdc/ad7152.c
> index dc6ecd824365..ff10d1f0a7e4 100644
> --- a/drivers/staging/iio/cdc/ad7152.c
> +++ b/drivers/staging/iio/cdc/ad7152.c
> @@ -231,16 +231,12 @@ static int ad7152_write_raw_samp_freq(struct device *dev, int val)
>  	if (i >= ARRAY_SIZE(ad7152_filter_rate_table))
>  		i = ARRAY_SIZE(ad7152_filter_rate_table) - 1;
>  
> -	mutex_lock(&chip->state_lock);
>  	ret = i2c_smbus_write_byte_data(chip->client,
>  					AD7152_REG_CFG2, AD7152_CFG2_OSR(i));
> -	if (ret < 0) {
> -		mutex_unlock(&chip->state_lock);
> +	if (ret < 0)
>  		return ret;
> -	}
>  
>  	chip->filter_rate_setup = i;
> -	mutex_unlock(&chip->state_lock);
>  
>  	return ret;
>  }
>