[PATCH 5.15 151/171] iio: dln2-adc: Fix lockdep complaint

Greg Kroah-Hartman
2021-12-13T10:08:00Z

From: Noralf Trønnes <noralf@tronnes.org>

commit 59f92868176f191eefde70d284bdfc1ed76a84bc upstream.

When reading the voltage:

$ cat /sys/bus/iio/devices/iio\:device0/in_voltage0_raw

Lockdep complains:

[ 153.910616] ======================================================
[ 153.916918] WARNING: possible circular locking dependency detected
[ 153.923221] 5.14.0+ #5 Not tainted
[ 153.926692] ------------------------------------------------------
[ 153.932992] cat/717 is trying to acquire lock:
[ 153.937525] c2585358 (&indio_dev->mlock){+.+.}-{3:3}, at: iio_device_claim_direct_mode+0x28/0x44
[ 153.946541]
but task is already holding lock:
[ 153.952487] c2585860 (&dln2->mutex){+.+.}-{3:3}, at: dln2_adc_read_raw+0x94/0x2bc [dln2_adc]
[ 153.961152]
which lock already depends on the new lock.

Fix this by not calling into the iio core underneath the dln2->mutex lock.

Fixes: 7c0299e879dd ("iio: adc: Add support for DLN2 ADC")
Cc: Jack Andersen <jackoalan@gmail.com>
Signed-off-by: Noralf Trønnes <noralf@tronnes.org>
Link: https://lore.kernel.org/r/20211018113731.25723-1-noralf@tronnes.org
Cc: <Stable@vger.kernel.org>
Signed-off-by: Jonathan Cameron <Jonathan.Cameron@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/iio/adc/dln2-adc.c | 15 +++++++--------
1 file changed, 7 insertions(+), 8 deletions(-)

--- a/drivers/iio/adc/dln2-adc.c
+++ b/drivers/iio/adc/dln2-adc.c
@@ -248,7 +248,6 @@ static int dln2_adc_set_chan_period(stru
static int dln2_adc_read(struct dln2_adc *dln2, unsigned int channel)
{
int ret, i;
- struct iio_dev *indio_dev = platform_get_drvdata(dln2->pdev);
u16 conflict;
__le16 value;
int olen = sizeof(value);
@@ -257,13 +256,9 @@ static int dln2_adc_read(struct dln2_adc
.chan = channel,
};

- ret = iio_device_claim_direct_mode(indio_dev);
- if (ret < 0)
- return ret;
-
ret = dln2_adc_set_chan_enabled(dln2, channel, true);
if (ret < 0)
- goto release_direct;
+ return ret;

ret = dln2_adc_set_port_enabled(dln2, true, &conflict);
if (ret < 0) {
@@ -300,8 +295,6 @@ disable_port:
dln2_adc_set_port_enabled(dln2, false, NULL);
disable_chan:
dln2_adc_set_chan_enabled(dln2, channel, false);
-release_direct:
- iio_device_release_direct_mode(indio_dev);

return ret;
}
@@ -337,10 +330,16 @@ static int dln2_adc_read_raw(struct iio_

switch (mask) {
case IIO_CHAN_INFO_RAW:
+ ret = iio_device_claim_direct_mode(indio_dev);
+ if (ret < 0)
+ return ret;
+
mutex_lock(&dln2->mutex);
ret = dln2_adc_read(dln2, chan->channel);
mutex_unlock(&dln2->mutex);

+ iio_device_release_direct_mode(indio_dev);
+
if (ret < 0)
return ret;