On Thu, Nov 20, 2025 at 04:29:07PM +0100, Simon Schippers wrote:
> Add __ptr_ring_consume_created_space() to check whether the previous
> __ptr_ring_consume() call successfully consumed an element and created
> space in the ring buffer. This enables callers to conditionally notify
> producers when space becomes available.
>
> The function is only valid immediately after a single consume operation
> and should not be used after calling __ptr_ring_consume_batched().
>
> Co-developed-by: Tim Gebauer <[email protected]>
> Signed-off-by: Tim Gebauer <[email protected]>
> Co-developed by: Jon Kohler <[email protected]>
> Signed-off-by: Jon Kohler <[email protected]>
> Signed-off-by: Simon Schippers <[email protected]>
> ---
> include/linux/ptr_ring.h | 17 +++++++++++++++++
> 1 file changed, 17 insertions(+)
>
> diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
> index da141cc8b075..76d6840b45a3 100644
> --- a/include/linux/ptr_ring.h
> +++ b/include/linux/ptr_ring.h
> @@ -453,6 +453,23 @@ static inline int ptr_ring_consume_batched_bh(struct
> ptr_ring *r,
> return ret;
> }
>
> +/*
> + * Check if the previous consume operation created space
space?
what does this mean?
> + *
> + * Returns true if the last call to __ptr_ring_consume() has created
> + * space in the ring buffer (i.e., an element was consumed).
> + *
> + * Note: This function is only valid immediately after a single call to
> + * __ptr_ring_consume(). If multiple calls to ptr_ring_consume*() have
> + * been made, this check must be performed after each call individually.
> + * Likewise, do not use this function after calling
> + * __ptr_ring_consume_batched().
API-wise, it is a really weird function. So is
{
p = __ptr_ring_consume
return !!p
}
guaranteed to be equivalent to
{
p = __ptr_ring_consume
return !!__ptr_ring_consume_created_space
}
> + */
> +static inline bool __ptr_ring_consume_created_space(struct ptr_ring *r)
> +{
> + return r->consumer_tail >= r->consumer_head;
> +}
> +
> /* Cast to structure type and call a function without discarding from FIFO.
> * Function must return a value.
> * Callers must take consumer_lock.
> --
> 2.43.0
