This patch moves the check for available free space for a new entry into a separate function. Existing callers that only check for a non-zero return value are unaffected; __ptr_ring_produce() now returns -EINVAL for a zero-size ring and -ENOSPC when full, whereas before both cases returned -ENOSPC. The new helper allows callers to determine in advance whether subsequent __ptr_ring_produce() calls will succeed. This information can, for example, be used to temporarily stop producing until __ptr_ring_check_produce() indicates that space is available again.
Co-developed-by: Tim Gebauer <[email protected]> Signed-off-by: Tim Gebauer <[email protected]> Signed-off-by: Simon Schippers <[email protected]> --- include/linux/ptr_ring.h | 20 ++++++++++++++++++-- 1 file changed, 18 insertions(+), 2 deletions(-) diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h index d2c3629bbe45..c95e891903f0 100644 --- a/include/linux/ptr_ring.h +++ b/include/linux/ptr_ring.h @@ -96,6 +96,20 @@ static inline bool ptr_ring_full_bh(struct ptr_ring *r) return ret; } +/* Note: callers invoking this in a loop must use a compiler barrier, + * for example cpu_relax(). Callers must hold producer_lock. + */ +static inline int __ptr_ring_check_produce(struct ptr_ring *r) +{ + if (unlikely(!r->size)) + return -EINVAL; + + if (data_race(r->queue[r->producer])) + return -ENOSPC; + + return 0; +} + /* Note: callers invoking this in a loop must use a compiler barrier, * for example cpu_relax(). Callers must hold producer_lock. * Callers are responsible for making sure pointer that is being queued @@ -103,8 +117,10 @@ static inline bool ptr_ring_full_bh(struct ptr_ring *r) */ static inline int __ptr_ring_produce(struct ptr_ring *r, void *ptr) { - if (unlikely(!r->size) || data_race(r->queue[r->producer])) - return -ENOSPC; + int p = __ptr_ring_check_produce(r); + + if (p) + return p; /* Make sure the pointer we are storing points to a valid data. */ /* Pairs with the dependency ordering in __ptr_ring_consume. */ -- 2.43.0
