linux-kernel - Re: [PATCH] iio: hi8435: fix race between event enable and event generation

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Date:   Wed, 24 May 2017 20:30:33 +0100
From:   Jonathan Cameron <jic23@...nel.org>
To:     Nikita Yushchenko <nikita.yoush@...entembedded.com>
Cc:     Hartmut Knaack <knaack.h@....de>,
        Lars-Peter Clausen <lars@...afoo.de>,
        Peter Meerwald-Stadler <pmeerw@...erw.net>,
        Sanchayan Maity <maitysanchayan@...il.com>,
        Gregor Boirie <gregor.boirie@...rot.com>,
        Matt Ranostay <mranostay@...il.com>, linux-iio@...r.kernel.org,
        linux-kernel@...r.kernel.org, Chris Healy <Chris.Healy@....aero>,
        Jeff White <Jeff.White@....aero>,
        Vladimir Barinov <vladimir.barinov@...entembedded.com>
Subject: Re: [PATCH] iio: hi8435: fix race between event enable and event
 generation

On Tue, 23 May 2017 11:07:29 +0300
Nikita Yushchenko <nikita.yoush@...entembedded.com> wrote:

> Add locking to avoid interference between reading/processing current
> sence in event enable and event generation paths.
> 
> Signed-off-by: Nikita Yushchenko <nikita.yoush@...entembedded.com>
Make sense.  Could you give a little more detail on the seriousness
of this bug?  I need to assess whether we just queue it up for the
next merge window or push it forward quicker as a bug fix and
whether to mark it for stable or not.

You probably have a better idea of how much it matters than I do!

Thanks,

Jonathan
> ---
>  drivers/iio/adc/hi8435.c | 8 ++++++++
>  1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/iio/adc/hi8435.c b/drivers/iio/adc/hi8435.c
> index ab59969b7c49..28fc699f00f6 100644
> --- a/drivers/iio/adc/hi8435.c
> +++ b/drivers/iio/adc/hi8435.c
> @@ -144,6 +144,8 @@ static int hi8435_write_event_config(struct iio_dev *idev,
>  	int ret;
>  	u32 tmp;
>  
> +	mutex_lock(&priv->lock);
> +
>  	if (state) {
>  		ret = hi8435_readl(priv, HI8435_SO31_0_REG, &tmp);
>  		if (ret < 0)
> @@ -157,6 +159,8 @@ static int hi8435_write_event_config(struct iio_dev *idev,
>  	} else
>  		priv->event_scan_mask &= ~BIT(chan->channel);
>  
> +	mutex_unlock(&priv->lock);
> +
>  	return 0;
>  }
>  
> @@ -449,12 +453,16 @@ static irqreturn_t hi8435_trigger_handler(int irq, void *private)
>  	u32 val;
>  	int ret;
>  
> +	mutex_lock(&priv->lock);
> +
>  	ret = hi8435_readl(priv, HI8435_SO31_0_REG, &val);
>  	if (ret < 0)
>  		goto err_read;
>  
>  	hi8435_iio_push_event(idev, val);
>  
> +	mutex_unlock(&priv->lock);
> +
>  err_read:
>  	iio_trigger_notify_done(idev->trig);
>