This is a note to let you know that I've just added the patch titled
iio: dln2-adc: Fix lockdep complaint
to my char-misc git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git in the char-misc-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 59f92868176f191eefde70d284bdfc1ed76a84bc Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Noralf=20Tr=C3=B8nnes?= noralf@tronnes.org Date: Mon, 18 Oct 2021 13:37:31 +0200 Subject: iio: dln2-adc: Fix lockdep complaint MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit
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 --- drivers/iio/adc/dln2-adc.c | 15 +++++++-------- 1 file changed, 7 insertions(+), 8 deletions(-)
diff --git a/drivers/iio/adc/dln2-adc.c b/drivers/iio/adc/dln2-adc.c index 16407664182c..6c67192946aa 100644 --- 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(struct dln2_adc *dln2, 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 *dln2, unsigned int channel) .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 @@ static int dln2_adc_read(struct dln2_adc *dln2, unsigned int channel) 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_dev *indio_dev,
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;