Re: [PATCH v2 2/9] iio: accel: bmc150: Don't make the remove function of the second accelerometer unregister itself

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 23 May 2021 19:00:56 +0200
Hans de Goede <hdegoede@redhat.com> wrote:

> On machines with dual accelerometers described in a single ACPI fwnode,
> the bmc150_accel_probe() instantiates a second i2c-client for the second
> accelerometer.
> 
> A pointer to this manually instantiated second i2c-client is stored
> inside the iio_dev's private-data through bmc150_set_second_device(),
> so that the i2c-client can be unregistered from bmc150_accel_remove().
> 
> Before this commit bmc150_set_second_device() took only 1 argument so it
> would store the pointer in private-data of the iio_dev belonging to the
> manually instantiated i2c-client, leading to the bmc150_accel_remove()
> call for the second_dev trying to unregister *itself* while it was
> being removed, leading to a deadlock and rmmod hanging.
> 
> Change bmc150_set_second_device() to take 2 arguments: 1. The i2c-client
> which is instantiating the second i2c-client for the 2nd accelerometer and
> 2. The second-device pointer itself (which also is an i2c-client).
> 
> This will store the second_device pointer in the private data of the
> iio_dev belonging to the (ACPI instantiated) i2c-client for the first
> accelerometer and will make bmc150_accel_remove() unregister the
> second_device i2c-client when called for the first client,
> avoiding the deadlock.
> 
> Fixes: 5bfb3a4bd8f6 ("iio: accel: bmc150: Check for a second ACPI device for BOSC0200")
> Cc: Jeremy Cline <jeremy@jcline.org>
> Signed-off-by: Hans de Goede <hdegoede@redhat.com>
Patches 1 and 2 applied to the fixes-togreg branch of iio.git and marked for stable.
The rest will have to wait for now.

Thanks,

Jonathan

> ---
>  drivers/iio/accel/bmc150-accel-core.c | 4 ++--
>  drivers/iio/accel/bmc150-accel-i2c.c  | 2 +-
>  drivers/iio/accel/bmc150-accel.h      | 2 +-
>  3 files changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/accel/bmc150-accel-core.c b/drivers/iio/accel/bmc150-accel-core.c
> index 3a3f67930165..8ff358c37a81 100644
> --- a/drivers/iio/accel/bmc150-accel-core.c
> +++ b/drivers/iio/accel/bmc150-accel-core.c
> @@ -1815,11 +1815,11 @@ struct i2c_client *bmc150_get_second_device(struct i2c_client *client)
>  }
>  EXPORT_SYMBOL_GPL(bmc150_get_second_device);
>  
> -void bmc150_set_second_device(struct i2c_client *client)
> +void bmc150_set_second_device(struct i2c_client *client, struct i2c_client *second_dev)
>  {
>  	struct bmc150_accel_data *data = iio_priv(i2c_get_clientdata(client));
>  
> -	data->second_device = client;
> +	data->second_device = second_dev;
>  }
>  EXPORT_SYMBOL_GPL(bmc150_set_second_device);
>  
> diff --git a/drivers/iio/accel/bmc150-accel-i2c.c b/drivers/iio/accel/bmc150-accel-i2c.c
> index 69f709319484..2afaae0294ee 100644
> --- a/drivers/iio/accel/bmc150-accel-i2c.c
> +++ b/drivers/iio/accel/bmc150-accel-i2c.c
> @@ -70,7 +70,7 @@ static int bmc150_accel_probe(struct i2c_client *client,
>  
>  		second_dev = i2c_acpi_new_device(&client->dev, 1, &board_info);
>  		if (!IS_ERR(second_dev))
> -			bmc150_set_second_device(second_dev);
> +			bmc150_set_second_device(client, second_dev);
>  	}
>  #endif
>  
> diff --git a/drivers/iio/accel/bmc150-accel.h b/drivers/iio/accel/bmc150-accel.h
> index 6024f15b9700..e30c1698f6fb 100644
> --- a/drivers/iio/accel/bmc150-accel.h
> +++ b/drivers/iio/accel/bmc150-accel.h
> @@ -18,7 +18,7 @@ int bmc150_accel_core_probe(struct device *dev, struct regmap *regmap, int irq,
>  			    const char *name, bool block_supported);
>  int bmc150_accel_core_remove(struct device *dev);
>  struct i2c_client *bmc150_get_second_device(struct i2c_client *second_device);
> -void bmc150_set_second_device(struct i2c_client *second_device);
> +void bmc150_set_second_device(struct i2c_client *client, struct i2c_client *second_dev);
>  extern const struct dev_pm_ops bmc150_accel_pm_ops;
>  extern const struct regmap_config bmc150_regmap_conf;
>