--- /dev/null
+/* SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (c) 2010-2017 Intel Corporation
+ * Copyright (c) 2007-2009 Kip Macy kmacy@freebsd.org
+ * All rights reserved.
+ * Derived from FreeBSD's bufring.h
+ * Used as BSD-3 Licensed with permission from Kip Macy.
+ */
+
+#ifndef _RTE_RING_GENERIC_H_
+#define _RTE_RING_GENERIC_H_
+
+static __rte_always_inline void
+update_tail(struct rte_ring_headtail *ht, uint32_t old_val, uint32_t new_val,
+ uint32_t single, uint32_t enqueue)
+{
+ if (enqueue)
+ rte_smp_wmb();
+ else
+ rte_smp_rmb();
+ /*
+ * If there are other enqueues/dequeues in progress that preceded us,
+ * we need to wait for them to complete
+ */
+ if (!single)
+ while (unlikely(ht->tail != old_val))
+ rte_pause();
+
+ ht->tail = new_val;
+}
+
+/**
+ * @internal This function updates the producer head for enqueue
+ *
+ * @param r
+ * A pointer to the ring structure
+ * @param is_sp
+ * Indicates whether multi-producer path is needed or not
+ * @param n
+ * The number of elements we will want to enqueue, i.e. how far should the
+ * head be moved
+ * @param behavior
+ * RTE_RING_QUEUE_FIXED: Enqueue a fixed number of items from a ring
+ * RTE_RING_QUEUE_VARIABLE: Enqueue as many items as possible from ring
+ * @param old_head
+ * Returns head value as it was before the move, i.e. where enqueue starts
+ * @param new_head
+ * Returns the current/new head value i.e. where enqueue finishes
+ * @param free_entries
+ * Returns the amount of free space in the ring BEFORE head was moved
+ * @return
+ * Actual number of objects enqueued.
+ * If behavior == RTE_RING_QUEUE_FIXED, this will be 0 or n only.
+ */
+static __rte_always_inline unsigned int
+__rte_ring_move_prod_head(struct rte_ring *r, int is_sp,
+ unsigned int n, enum rte_ring_queue_behavior behavior,
+ uint32_t *old_head, uint32_t *new_head,
+ uint32_t *free_entries)
+{
+ const uint32_t capacity = r->capacity;
+ unsigned int max = n;
+ int success;
+
+ do {
+ /* Reset n to the initial burst count */
+ n = max;
+
+ *old_head = r->prod.head;
+
+ /* add rmb barrier to avoid load/load reorder in weak
+ * memory model. It is noop on x86
+ */
+ rte_smp_rmb();
+
+ const uint32_t cons_tail = r->cons.tail;
+ /*
+ * The subtraction is done between two unsigned 32bits value
+ * (the result is always modulo 32 bits even if we have
+ * *old_head > cons_tail). So 'free_entries' is always between 0
+ * and capacity (which is < size).
+ */
+ *free_entries = (capacity + cons_tail - *old_head);
+
+ /* check that we have enough room in ring */
+ if (unlikely(n > *free_entries))
+ n = (behavior == RTE_RING_QUEUE_FIXED) ?
+ 0 : *free_entries;
+
+ if (n == 0)
+ return 0;
+
+ *new_head = *old_head + n;
+ if (is_sp)
+ r->prod.head = *new_head, success = 1;
+ else
+ success = rte_atomic32_cmpset(&r->prod.head,
+ *old_head, *new_head);
+ } while (unlikely(success == 0));
+ return n;
+}
+
+/**
+ * @internal This function updates the consumer head for dequeue
+ *
+ * @param r
+ * A pointer to the ring structure
+ * @param is_sc
+ * Indicates whether multi-consumer path is needed or not
+ * @param n
+ * The number of elements we will want to enqueue, i.e. how far should the
+ * head be moved
+ * @param behavior
+ * RTE_RING_QUEUE_FIXED: Dequeue a fixed number of items from a ring
+ * RTE_RING_QUEUE_VARIABLE: Dequeue as many items as possible from ring
+ * @param old_head
+ * Returns head value as it was before the move, i.e. where dequeue starts
+ * @param new_head
+ * Returns the current/new head value i.e. where dequeue finishes
+ * @param entries
+ * Returns the number of entries in the ring BEFORE head was moved
+ * @return
+ * - Actual number of objects dequeued.
+ * If behavior == RTE_RING_QUEUE_FIXED, this will be 0 or n only.
+ */
+static __rte_always_inline unsigned int
+__rte_ring_move_cons_head(struct rte_ring *r, int is_sc,
+ unsigned int n, enum rte_ring_queue_behavior behavior,
+ uint32_t *old_head, uint32_t *new_head,
+ uint32_t *entries)
+{
+ unsigned int max = n;
+ int success;
+
+ /* move cons.head atomically */
+ do {
+ /* Restore n as it may change every loop */
+ n = max;
+
+ *old_head = r->cons.head;
+
+ /* add rmb barrier to avoid load/load reorder in weak
+ * memory model. It is noop on x86
+ */
+ rte_smp_rmb();
+
+ const uint32_t prod_tail = r->prod.tail;
+ /* The subtraction is done between two unsigned 32bits value
+ * (the result is always modulo 32 bits even if we have
+ * cons_head > prod_tail). So 'entries' is always between 0
+ * and size(ring)-1.
+ */
+ *entries = (prod_tail - *old_head);
+
+ /* Set the actual entries for dequeue */
+ if (n > *entries)
+ n = (behavior == RTE_RING_QUEUE_FIXED) ? 0 : *entries;
+
+ if (unlikely(n == 0))
+ return 0;
+
+ *new_head = *old_head + n;
+ if (is_sc)
+ r->cons.head = *new_head, success = 1;
+ else
+ success = rte_atomic32_cmpset(&r->cons.head, *old_head,
+ *new_head);
+ } while (unlikely(success == 0));
+ return n;
+}
+
+#endif /* _RTE_RING_GENERIC_H_ */
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