Patchwork staging: iio: ad7152: Fix deadlock in ad7152_write_raw_samp_freq()

login
register
mail settings
Submitter Alexey Khoroshilov
Date May 26, 2017, 10:53 p.m.
Message ID <1495839184-28468-1-git-send-email-khoroshilov@ispras.ru>
Download mbox | patch
Permalink /patch/9751347/
State New
Headers show

Comments

Alexey Khoroshilov - May 26, 2017, 10:53 p.m.
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@ispras.ru>
---
 drivers/staging/iio/cdc/ad7152.c | 6 +-----
 1 file changed, 1 insertion(+), 5 deletions(-)
Lars-Peter Clausen - May 28, 2017, 9:47 a.m.
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@ispras.ru>

Looks good, thanks.

Fixes: 6572389bcc11 ("staging: iio: cdc: ad7152: Implement
IIO_CHAN_INFO_SAMP_FREQ attribute")
Acked-by: Lars-Peter Clausen <lars@metafoo.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;
>  }
>
Jonathan Cameron - May 28, 2017, 2:46 p.m.
On Sun, 28 May 2017 11:47:04 +0200
Lars-Peter Clausen <lars@metafoo.de> wrote:

> 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@ispras.ru>  
> 
> Looks good, thanks.
> 
> Fixes: 6572389bcc11 ("staging: iio: cdc: ad7152: Implement
> IIO_CHAN_INFO_SAMP_FREQ attribute")
> Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Applied to the fixes-togreg branch of iio.git.

Thanks,

Jonathan
> 
> 
> > ---
> >  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;
> >  }
> >   
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-iio" in
> the body of a message to majordomo@vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html

Patch

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;
 }