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Date:   Wed, 23 Nov 2022 20:39:57 +0000
From:   Jonathan Cameron <jic23@kernel.org>
To:     Ramona Bolboaca <ramona.bolboaca@analog.com>
Cc:     <nuno.sa@analog.com>, <linux-iio@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v6 1/9] iio: adis: add '__adis_enable_irq()'
 implementation
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In-Reply-To: <20221122082757.449452-2-ramona.bolboaca@analog.com>
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        <20221122082757.449452-2-ramona.bolboaca@analog.com>
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On Tue, 22 Nov 2022 10:27:49 +0200
Ramona Bolboaca <ramona.bolboaca@analog.com> wrote:

> Add '__adis_enable_irq()' implementation which is the unlocked
> version of 'adis_enable_irq()'.
> Call '__adis_enable_irq()' instead of 'adis_enable_irq()' from
> '__adis_intial_startup()' to keep the expected unlocked functionality.
>=20
> This fix is needed to remove a deadlock for all devices which are
> using 'adis_initial_startup()'. The deadlock occurs because the
> same mutex is acquired twice, without releasing it.
> The mutex is acquired once inside 'adis_initial_startup()', before
> calling '__adis_initial_startup()', and once inside
> 'adis_enable_irq()', which is called by '__adis_initial_startup()'.
> The deadlock is removed by calling '__adis_enable_irq()', instead of
> 'adis_enable_irq()' from within '__adis_initial_startup()'.
>=20
> Fixes: b600bd7eb3335 ("iio: adis: do not disabe IRQs in 'adis_init()'")
> Signed-off-by: Ramona Bolboaca <ramona.bolboaca@analog.com>
> Reviewed-by: Nuno S=C3=A1 <nuno.sa@analog.com>
Build issue in here that I've fixed up.

> ---
>  drivers/iio/imu/adis.c       | 28 ++++++++++------------------
>  include/linux/iio/imu/adis.h | 13 ++++++++++++-
>  2 files changed, 22 insertions(+), 19 deletions(-)
>=20
> diff --git a/drivers/iio/imu/adis.c b/drivers/iio/imu/adis.c
> index f7fcfd04f659..bc40240b29e2 100644
> --- a/drivers/iio/imu/adis.c
> +++ b/drivers/iio/imu/adis.c
> @@ -270,23 +270,19 @@ EXPORT_SYMBOL_NS(adis_debugfs_reg_access, IIO_ADISL=
IB);
>  #endif
> =20
>  /**
> - * adis_enable_irq() - Enable or disable data ready IRQ
> + * __adis_enable_irq() - Enable or disable data ready IRQ (unlocked)
>   * @adis: The adis device
>   * @enable: Whether to enable the IRQ
>   *
>   * Returns 0 on success, negative error code otherwise
>   */
> -int adis_enable_irq(struct adis *adis, bool enable)
> +int __adis_enable_irq(struct adis *adis, bool enable)
>  {
> -	int ret =3D 0;
> +	int ret;
>  	u16 msc;
> =20
> -	mutex_lock(&adis->state_lock);
> -
> -	if (adis->data->enable_irq) {
> -		ret =3D adis->data->enable_irq(adis, enable);
> -		goto out_unlock;
> -	}
> +	if (adis->data->enable_irq)
> +		return adis->data->enable_irq(adis, enable);
> =20
>  	if (adis->data->unmasked_drdy) {
>  		if (enable)
> @@ -294,12 +290,12 @@ int adis_enable_irq(struct adis *adis, bool enable)
>  		else
>  			disable_irq(adis->spi->irq);
> =20
> -		goto out_unlock;
> +		return 0;
>  	}
> =20
>  	ret =3D __adis_read_reg_16(adis, adis->data->msc_ctrl_reg, &msc);
>  	if (ret)
> -		goto out_unlock;
> +		return ret;
> =20
>  	msc |=3D ADIS_MSC_CTRL_DATA_RDY_POL_HIGH;
>  	msc &=3D ~ADIS_MSC_CTRL_DATA_RDY_DIO2;
> @@ -308,13 +304,9 @@ int adis_enable_irq(struct adis *adis, bool enable)
>  	else
>  		msc &=3D ~ADIS_MSC_CTRL_DATA_RDY_EN;
> =20
> -	ret =3D __adis_write_reg_16(adis, adis->data->msc_ctrl_reg, msc);
> -
> -out_unlock:
> -	mutex_unlock(&adis->state_lock);
> -	return ret;
> +	return __adis_write_reg_16(adis, adis->data->msc_ctrl_reg, msc);
>  }
> -EXPORT_SYMBOL_NS(adis_enable_irq, IIO_ADISLIB);
> +EXPORT_SYMBOL_NS(__adis_enable_irq, IIO_ADISLIB);
> =20
>  /**
>   * __adis_check_status() - Check the device for error conditions (unlock=
ed)
> @@ -445,7 +437,7 @@ int __adis_initial_startup(struct adis *adis)
>  	 * with 'IRQF_NO_AUTOEN' anyways.
>  	 */
>  	if (!adis->data->unmasked_drdy)
> -		adis_enable_irq(adis, false);
> +		__adis_enable_irq(adis, false);
> =20
>  	if (!adis->data->prod_id_reg)
>  		return 0;
> diff --git a/include/linux/iio/imu/adis.h b/include/linux/iio/imu/adis.h
> index 515ca09764fe..d789ecf8d0c8 100644
> --- a/include/linux/iio/imu/adis.h
> +++ b/include/linux/iio/imu/adis.h
> @@ -402,9 +402,20 @@ static inline int adis_update_bits_base(struct adis =
*adis, unsigned int reg,
>  	__adis_update_bits_base(adis, reg, mask, val, sizeof(val));	\
>  })
> =20
> -int adis_enable_irq(struct adis *adis, bool enable);
> +static inline int adis_enable_irq(struct adis *adis, bool enable)
> +{
> +	int ret;
> +
> +	mutex_lock(&adis->state_lock);
> +	ret =3D __adis_enable_irq(adis, enable);
> +	mutex_unlock(&adis->state_lock);
> +
> +	return ret;
> +}
> +
>  int __adis_check_status(struct adis *adis);
>  int __adis_initial_startup(struct adis *adis);
> +int __adis_enable_irq(struct adis *adis, bool enable);

Move the above down here seeing as __adis_enable_irq() isn't
defined until this point (and that gave a bunch of build issues).

> =20
>  static inline int adis_check_status(struct adis *adis)
>  {