linux-kernel - Re: [PATCH v7] iio: adc: max1363: replace uses of mlock

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Message-ID: <20200330143921.6ecf8800@archlinux>
Date:   Mon, 30 Mar 2020 14:39:21 +0100
From:   Jonathan Cameron <jic23@...23.retrosnub.co.uk>
To:     Rohit Sarkar <rohitsarkar5398@...il.com>
Cc:     linux-iio@...r.kernel.org, linux-kernel@...r.kernel.org,
        dragos.bogdan@...log.com
Subject: Re: [PATCH v7] iio: adc: max1363: replace uses of mlock

On Sun, 22 Mar 2020 17:53:58 +0000
Jonathan Cameron <jic23@...nel.org> wrote:

> On Sun, 15 Mar 2020 21:34:58 +0530
> Rohit Sarkar <rohitsarkar5398@...il.com> wrote:
> 
> > Replace usage indio_dev's mlock with either local lock or
> > iio_device_claim_direct_mode.
> > 
> > Signed-off-by: Rohit Sarkar <rohitsarkar5398@...il.com>  
> Applied to the togreg branch of iio.git and pushed out as testing.

Not my best review and strangely missed any warnings in my
local build tests.  0-day came back pointing this out earlier
(see inline).  I've fixed up.

> 
> Thanks,
> 
> Jonathan
> 
> > ---
> > Changelog v6 -> v7
> > * Fix failure handling logic
> > 
> > Changelog v5 -> v6
> > * Minor failure handling fixes
> > 
> > Changelog v4 -> v5
> > * Use local lock too at places where driver state needs to be protected.
> > 
> > Changelog v3 -> v4
> > * Fix indentation
> > 
> > Changelog v2 -> v3
> > * use iio_device_claim_direct when switching modes
> > * replace mlock usage in max1363_write_event_config
> > 
> > Changelog v1 -> v2
> > * Fix indentation
> > 
> >  drivers/iio/adc/max1363.c | 37 ++++++++++++++++++++++++++++---------
> >  1 file changed, 28 insertions(+), 9 deletions(-)
> > 
> > diff --git a/drivers/iio/adc/max1363.c b/drivers/iio/adc/max1363.c
> > index 5c2cc61b666e..12d72bf3f12a 100644
> > --- a/drivers/iio/adc/max1363.c
> > +++ b/drivers/iio/adc/max1363.c
> > @@ -150,6 +150,7 @@ struct max1363_chip_info {
> >   * @current_mode:	the scan mode of this chip
> >   * @requestedmask:	a valid requested set of channels
> >   * @reg:		supply regulator
> > + * @lock		lock to ensure state is consistent
> >   * @monitor_on:		whether monitor mode is enabled
> >   * @monitor_speed:	parameter corresponding to device monitor speed setting
> >   * @mask_high:		bitmask for enabled high thresholds
> > @@ -169,6 +170,7 @@ struct max1363_state {
> >  	const struct max1363_mode	*current_mode;
> >  	u32				requestedmask;
> >  	struct regulator		*reg;
> > +	struct mutex			lock;
> >  
> >  	/* Using monitor modes and buffer at the same time is
> >  	   currently not supported */
> > @@ -364,7 +366,13 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev,
> >  	struct max1363_state *st = iio_priv(indio_dev);
> >  	struct i2c_client *client = st->client;
> >  
> > -	mutex_lock(&indio_dev->mlock);
> > +	ret = iio_device_claim_direct_mode(indio_dev);
> > +	if (ret)
> > +		return ret;
> > +	mutex_lock(&st->lock);
> > +
> > +	if (ret < 0)
> > +		goto error_ret;
> >  	/*
> >  	 * If monitor mode is enabled, the method for reading a single
> >  	 * channel will have to be rather different and has not yet
> > @@ -372,7 +380,7 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev,
> >  	 *
> >  	 * Also, cannot read directly if buffered capture enabled.
> >  	 */
> > -	if (st->monitor_on || iio_buffer_enabled(indio_dev)) {
> > +	if (st->monitor_on) {
> >  		ret = -EBUSY;
> >  		goto error_ret;
> >  	}
> > @@ -404,8 +412,10 @@ static int max1363_read_single_chan(struct iio_dev *indio_dev,
> >  		data = rxbuf[0];
> >  	}
> >  	*val = data;
> > +
> >  error_ret:
> > -	mutex_unlock(&indio_dev->mlock);
> > +	mutex_unlock(&st->lock);
> > +	iio_device_release_direct_mode(indio_dev);
> >  	return ret;
> >  
> >  }
> > @@ -705,9 +715,9 @@ static ssize_t max1363_monitor_store_freq(struct device *dev,
> >  	if (!found)
> >  		return -EINVAL;
> >  
> > -	mutex_lock(&indio_dev->mlock);
> > +	mutex_lock(&st->lock);
> >  	st->monitor_speed = i;
> > -	mutex_unlock(&indio_dev->mlock);
> > +	mutex_unlock(&st->lock);
> >  
> >  	return 0;
> >  }
> > @@ -810,12 +820,12 @@ static int max1363_read_event_config(struct iio_dev *indio_dev,
> >  	int val;
> >  	int number = chan->channel;
> >  
> > -	mutex_lock(&indio_dev->mlock);
> > +	mutex_lock(&st->lock);
> >  	if (dir == IIO_EV_DIR_FALLING)
> >  		val = (1 << number) & st->mask_low;
> >  	else
> >  		val = (1 << number) & st->mask_high;
> > -	mutex_unlock(&indio_dev->mlock);
> > +	mutex_unlock(&st->lock);
> >  
> >  	return val;
> >  }
> > @@ -962,7 +972,14 @@ static int max1363_write_event_config(struct iio_dev *indio_dev,
> >  	u16 unifiedmask;
> >  	int number = chan->channel;
> >  
> > -	mutex_lock(&indio_dev->mlock);
> > +	ret = iio_device_claim_direct_mode(indio_dev);
> > +	if (ret)
> > +		return ret;
> > +	mutex_lock(&st->lock);
> > +

We just checked ret. No need to do it again :)

I've dropped this second test.

Jonathan


> > +	if (ret < 0)
> > +		goto error_ret;
> > +
> >  	unifiedmask = st->mask_low | st->mask_high;
> >  	if (dir == IIO_EV_DIR_FALLING) {
> >  
> > @@ -989,7 +1006,8 @@ static int max1363_write_event_config(struct iio_dev *indio_dev,
> >  
> >  	max1363_monitor_mode_update(st, !!(st->mask_high | st->mask_low));
> >  error_ret:
> > -	mutex_unlock(&indio_dev->mlock);
> > +	mutex_unlock(&st->lock);
> > +	iio_device_release_direct_mode(indio_dev);
> >  
> >  	return ret;
> >  }
> > @@ -1587,6 +1605,7 @@ static int max1363_probe(struct i2c_client *client,
> >  
> >  	st = iio_priv(indio_dev);
> >  
> > +	mutex_init(&st->lock);
> >  	st->reg = devm_regulator_get(&client->dev, "vcc");
> >  	if (IS_ERR(st->reg)) {
> >  		ret = PTR_ERR(st->reg);  
>