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

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Date:   Sun, 28 May 2017 15:46:48 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Lars-Peter Clausen <lars@...afoo.de>
Cc:     Alexey Khoroshilov <khoroshilov@...ras.ru>,
        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, ldv-project@...uxtesting.org
Subject: Re: [PATCH] staging: iio: ad7152: Fix deadlock in
 ad7152_write_raw_samp_freq()

On Sun, 28 May 2017 11:47:04 +0200
Lars-Peter Clausen <lars@...afoo.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@...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>
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;
> >  }
> >   
> 
> --
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