The implementation is inspired by ptr_ring_empty.
Co-developed-by: Tim Gebauer <tim.gebauer@xxxxxxxxxxxxxx>
Signed-off-by: Tim Gebauer <tim.gebauer@xxxxxxxxxxxxxx>
Signed-off-by: Simon Schippers <simon.schippers@xxxxxxxxxxxxxx>
---
include/linux/ptr_ring.h | 71 ++++++++++++++++++++++++++++++++++++++++
1 file changed, 71 insertions(+)
diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h
index 551329220e4f..6b8cfaecf478 100644
--- a/include/linux/ptr_ring.h
+++ b/include/linux/ptr_ring.h
@@ -243,6 +243,77 @@ static inline bool ptr_ring_empty_bh(struct ptr_ring *r)
return ret;
}
+/*
+ * Check if a spare capacity of cnt is available without taking any locks.
+ *
+ * If cnt==0 or cnt > r->size it acts the same as __ptr_ring_empty.
+ *
+ * The same requirements apply as described for __ptr_ring_empty.
+ */
+static inline bool __ptr_ring_spare(struct ptr_ring *r, int cnt)
+{
+ int size = r->size;
+ int to_check;
+
+ if (unlikely(!size || cnt < 0))
+ return true;
+
+ if (cnt > size)
+ cnt = 0;
+
+ to_check = READ_ONCE(r->consumer_head) - cnt;
+
+ if (to_check < 0)
+ to_check += size;
+
+ return !r->queue[to_check];
+}
+
+static inline bool ptr_ring_spare(struct ptr_ring *r, int cnt)
+{
+ bool ret;
+
+ spin_lock(&r->consumer_lock);
+ ret = __ptr_ring_spare(r, cnt);
+ spin_unlock(&r->consumer_lock);
+
+ return ret;
+}
+
+static inline bool ptr_ring_spare_irq(struct ptr_ring *r, int cnt)
+{
+ bool ret;
+
+ spin_lock_irq(&r->consumer_lock);
+ ret = __ptr_ring_spare(r, cnt);
+ spin_unlock_irq(&r->consumer_lock);
+
+ return ret;
+}
+
+static inline bool ptr_ring_spare_any(struct ptr_ring *r, int cnt)
+{
+ unsigned long flags;
+ bool ret;
+
+ spin_lock_irqsave(&r->consumer_lock, flags);
+ ret = __ptr_ring_spare(r, cnt);
+ spin_unlock_irqrestore(&r->consumer_lock, flags);
+
+ return ret;
+}
+
+static inline bool ptr_ring_spare_bh(struct ptr_ring *r, int cnt)
+{
+ bool ret;
+
+ spin_lock_bh(&r->consumer_lock);
+ ret = __ptr_ring_spare(r, cnt);
+ spin_unlock_bh(&r->consumer_lock);
+
+ return ret;
+}
+
/* Must only be called after __ptr_ring_peek returned !NULL */
static inline void __ptr_ring_discard_one(struct ptr_ring *r)
{
--
2.43.0
