[PATCH] iio: proximity: rfd77402: Fix completion race condition in IRQ mode

[PATCH] iio: proximity: rfd77402: Fix completion race condition in IRQ mode

[Felix Gu]

In IRQ mode, the completion was being reinitialized after the
measurement command had already been sent to the hardware. This
created a race condition where the IRQ handler could call complete()
before reinit_completion() was executed. Consequently,
wait_for_completion_timeout() would fail to see the signal and wait
until it timed out.

Move reinit_completion() to occur before the measurement command is
triggered to ensure the synchronization primitive is ready to
capture the interrupt.

Fixes: dc81be96a73a ("iio: proximity: rfd77402: Add interrupt handling support")
Signed-off-by: Felix Gu <ustc.gu@gmail.com>
---
 drivers/iio/proximity/rfd77402.c | 7 ++++---
 1 file changed, 4 insertions(+), 3 deletions(-)

diff --git a/drivers/iio/proximity/rfd77402.c b/drivers/iio/proximity/rfd77402.c
index 6afdbfca3e5a..81b8daf17a54 100644
--- a/drivers/iio/proximity/rfd77402.c
+++ b/drivers/iio/proximity/rfd77402.c
@@ -173,10 +173,8 @@ static int rfd77402_wait_for_result(struct rfd77402_data *data)
 	struct i2c_client *client = data->client;
 	int val, ret;
 
-	if (data->irq_en) {
-		reinit_completion(&data->completion);
+	if (data->irq_en)
 		return rfd77402_wait_for_irq(data);
-	}
 
 	/*
 	 * As per RFD77402 datasheet section '3.1.1 Single Measure', the
@@ -204,6 +202,9 @@ static int rfd77402_measure(struct rfd77402_data *data)
 	if (ret < 0)
 		return ret;
 
+	if (data->irq_en)
+		reinit_completion(&data->completion);
+
 	ret = i2c_smbus_write_byte_data(client, RFD77402_CMD_R,
 					RFD77402_CMD_SINGLE |
 					RFD77402_CMD_VALID);

---
base-commit: c025f6cf4209e1542ec2afebe49f42bbaf1a5c7b
change-id: 20260304-77402-ec479de1b9f6

Best regards,
-- 
Felix Gu <ustc.gu@gmail.com>

Re: [PATCH] iio: proximity: rfd77402: Fix completion race condition in IRQ mode

[Jonathan Cameron]

On Wed, 04 Mar 2026 22:14:32 +0800
Felix Gu <ustc.gu@gmail.com> wrote:

> In IRQ mode, the completion was being reinitialized after the
> measurement command had already been sent to the hardware. This
> created a race condition where the IRQ handler could call complete()
> before reinit_completion() was executed. Consequently,
> wait_for_completion_timeout() would fail to see the signal and wait
> until it timed out.
> 
> Move reinit_completion() to occur before the measurement command is
> triggered to ensure the synchronization primitive is ready to
> capture the interrupt.
> 
> Fixes: dc81be96a73a ("iio: proximity: rfd77402: Add interrupt handling support")
> Signed-off-by: Felix Gu <ustc.gu@gmail.com>

Looks good to me. Shrikant, you know this driver better than I do so if you
can take a look as well that would be great.

Thanks,

J
> ---
>  drivers/iio/proximity/rfd77402.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iio/proximity/rfd77402.c b/drivers/iio/proximity/rfd77402.c
> index 6afdbfca3e5a..81b8daf17a54 100644
> --- a/drivers/iio/proximity/rfd77402.c
> +++ b/drivers/iio/proximity/rfd77402.c
> @@ -173,10 +173,8 @@ static int rfd77402_wait_for_result(struct rfd77402_data *data)
>  	struct i2c_client *client = data->client;
>  	int val, ret;
>  
> -	if (data->irq_en) {
> -		reinit_completion(&data->completion);
> +	if (data->irq_en)
>  		return rfd77402_wait_for_irq(data);
> -	}
>  
>  	/*
>  	 * As per RFD77402 datasheet section '3.1.1 Single Measure', the
> @@ -204,6 +202,9 @@ static int rfd77402_measure(struct rfd77402_data *data)
>  	if (ret < 0)
>  		return ret;
>  
> +	if (data->irq_en)
> +		reinit_completion(&data->completion);
> +
>  	ret = i2c_smbus_write_byte_data(client, RFD77402_CMD_R,
>  					RFD77402_CMD_SINGLE |
>  					RFD77402_CMD_VALID);
> 
> ---
> base-commit: c025f6cf4209e1542ec2afebe49f42bbaf1a5c7b
> change-id: 20260304-77402-ec479de1b9f6
> 
> Best regards,

Re: [PATCH] iio: proximity: rfd77402: Fix completion race condition in IRQ mode

[Shrikant]

On Wed, Mar 4, 2026 at 7:44 PM Felix Gu <ustc.gu@gmail.com> wrote:
>
> In IRQ mode, the completion was being reinitialized after the
> measurement command had already been sent to the hardware. This
> created a race condition where the IRQ handler could call complete()
> before reinit_completion() was executed. Consequently,
> wait_for_completion_timeout() would fail to see the signal and wait
> until it timed out.
>
> Move reinit_completion() to occur before the measurement command is
> triggered to ensure the synchronization primitive is ready to
> capture the interrupt.
>
> Fixes: dc81be96a73a ("iio: proximity: rfd77402: Add interrupt handling support")
> Signed-off-by: Felix Gu <ustc.gu@gmail.com>
> ---
>  drivers/iio/proximity/rfd77402.c | 7 ++++---
>  1 file changed, 4 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iio/proximity/rfd77402.c b/drivers/iio/proximity/rfd77402.c
> index 6afdbfca3e5a..81b8daf17a54 100644
> --- a/drivers/iio/proximity/rfd77402.c
> +++ b/drivers/iio/proximity/rfd77402.c
> @@ -173,10 +173,8 @@ static int rfd77402_wait_for_result(struct rfd77402_data *data)
>         struct i2c_client *client = data->client;
>         int val, ret;
>
> -       if (data->irq_en) {
> -               reinit_completion(&data->completion);
> +       if (data->irq_en)
>                 return rfd77402_wait_for_irq(data);
> -       }
>
>         /*
>          * As per RFD77402 datasheet section '3.1.1 Single Measure', the
> @@ -204,6 +202,9 @@ static int rfd77402_measure(struct rfd77402_data *data)
>         if (ret < 0)
>                 return ret;
>
> +       if (data->irq_en)
> +               reinit_completion(&data->completion);
> +
Looks good to me.
Reviewed-by: Shrikant Raskar <raskar.shree97@gmail.com>

Regards,
Shrikant

Re: [PATCH] iio: proximity: rfd77402: Fix completion race condition in IRQ mode

[Jonathan Cameron]

On Mon, 9 Mar 2026 22:32:58 +0530
Shrikant <raskar.shree97@gmail.com> wrote:

> On Wed, Mar 4, 2026 at 7:44 PM Felix Gu <ustc.gu@gmail.com> wrote:
> >
> > In IRQ mode, the completion was being reinitialized after the
> > measurement command had already been sent to the hardware. This
> > created a race condition where the IRQ handler could call complete()
> > before reinit_completion() was executed. Consequently,
> > wait_for_completion_timeout() would fail to see the signal and wait
> > until it timed out.
> >
> > Move reinit_completion() to occur before the measurement command is
> > triggered to ensure the synchronization primitive is ready to
> > capture the interrupt.
> >
> > Fixes: dc81be96a73a ("iio: proximity: rfd77402: Add interrupt handling support")
> > Signed-off-by: Felix Gu <ustc.gu@gmail.com>
> > ---
> >  drivers/iio/proximity/rfd77402.c | 7 ++++---
> >  1 file changed, 4 insertions(+), 3 deletions(-)
> >
> > diff --git a/drivers/iio/proximity/rfd77402.c b/drivers/iio/proximity/rfd77402.c
> > index 6afdbfca3e5a..81b8daf17a54 100644
> > --- a/drivers/iio/proximity/rfd77402.c
> > +++ b/drivers/iio/proximity/rfd77402.c
> > @@ -173,10 +173,8 @@ static int rfd77402_wait_for_result(struct rfd77402_data *data)
> >         struct i2c_client *client = data->client;
> >         int val, ret;
> >
> > -       if (data->irq_en) {
> > -               reinit_completion(&data->completion);
> > +       if (data->irq_en)
> >                 return rfd77402_wait_for_irq(data);
> > -       }
> >
> >         /*
> >          * As per RFD77402 datasheet section '3.1.1 Single Measure', the
> > @@ -204,6 +202,9 @@ static int rfd77402_measure(struct rfd77402_data *data)
> >         if (ret < 0)
> >                 return ret;
> >
> > +       if (data->irq_en)
> > +               reinit_completion(&data->completion);
> > +  
> Looks good to me.
> Reviewed-by: Shrikant Raskar <raskar.shree97@gmail.com>
> 
Applied to the fixes-togreg branch of iio.git. Note I just sent a pull
request on that so will probably rebase after that (hopefully) gets
merged into char-misc-linus.

Thanks,

Jonathan
> Regards,
> Shrikant