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

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>
Fixes: 6572389bcc11 ("staging: iio: cdc: ad7152: Implement
IIO_CHAN_INFO_SAMP_FREQ attribute")
Acked-by: Lars-Peter Clausen <lars@metafoo.de>
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <jic23@kernel.org>

diff --git a/drivers/staging/iio/cdc/ad7152.c b/drivers/staging/iio/cdc/ad7152.c
index dc6ecd8..ff10d1f 100644 (file)
--- 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;
 }