On Fri, Mar 13, 2020 at 05:31:33PM +0530, Syed Nayyar Waris wrote:
> Add lock protection from race conditions in the 104-quad-8 counter
> driver for differential encoder cable status changes. There is no IRQ
> handling so use spin_lock calls for protection.
>
> Fixes: bbef69e088c3 ("counter: 104-quad-8: Support Differential Encoder Cable Status")
>
> Signed-off-by: Syed Nayyar Waris <syednwaris@xxxxxxxxx>
Signed-off-by: William Breathitt Gray <vilhelm.gray@xxxxxxxxx>
> ---
> Changes in v4:
> - Shift review-comments section so that it is not saved in commit message.
> - Add spin_unlock calls for deadlock avoidance.
> - Few changes related to casting.
>
> drivers/counter/104-quad-8.c | 18 +++++++++++++++---
> 1 file changed, 15 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/counter/104-quad-8.c b/drivers/counter/104-quad-8.c
> index 9dab190..c9e227f 100644
> --- a/drivers/counter/104-quad-8.c
> +++ b/drivers/counter/104-quad-8.c
> @@ -1151,18 +1151,26 @@ static ssize_t quad8_signal_cable_fault_read(struct counter_device *counter,
> struct counter_signal *signal,
> void *private, char *buf)
> {
> - const struct quad8_iio *const priv = counter->priv;
> + struct quad8_iio *const priv = counter->priv;
> const size_t channel_id = signal->id / 2;
> - const bool disabled = !(priv->cable_fault_enable & BIT(channel_id));
> + bool disabled;
> unsigned int status;
> unsigned int fault;
>
> - if (disabled)
> + spin_lock(&priv->lock);
> +
> + disabled = !(priv->cable_fault_enable & BIT(channel_id));
> +
> + if (disabled) {
> + spin_unlock(&priv->lock);
> return -EINVAL;
> + }
>
> /* Logic 0 = cable fault */
> status = inb(priv->base + QUAD8_DIFF_ENCODER_CABLE_STATUS);
>
> + spin_unlock(&priv->lock);
> +
> /* Mask respective channel and invert logic */
> fault = !(status & BIT(channel_id));
>
> @@ -1194,6 +1202,8 @@ static ssize_t quad8_signal_cable_fault_enable_write(
> if (ret)
> return ret;
>
> + spin_lock(&priv->lock);
> +
> if (enable)
> priv->cable_fault_enable |= BIT(channel_id);
> else
> @@ -1204,6 +1214,8 @@ static ssize_t quad8_signal_cable_fault_enable_write(
>
> outb(cable_fault_enable, priv->base + QUAD8_DIFF_ENCODER_CABLE_STATUS);
>
> + spin_unlock(&priv->lock);
> +
> return len;
> }
>
> --
> 2.7.4
>
Attachment:
signature.asc
Description: PGP signature
