diff --git a/lib/librte_ring/Makefile b/lib/librte_ring/Makefile
index 04e446e37..f75d8e530 100644
--- a/lib/librte_ring/Makefile
+++ b/lib/librte_ring/Makefile
@@ -20,6 +20,8 @@ SYMLINK-$(CONFIG_RTE_LIBRTE_RING)-include := rte_ring.h \
 					rte_ring_elem.h \
 					rte_ring_generic.h \
 					rte_ring_c11_mem.h \
+					rte_ring_hts.h \
+					rte_ring_hts_c11_mem.h \
 					rte_ring_rts.h \
 					rte_ring_rts_c11_mem.h
 
diff --git a/lib/librte_ring/meson.build b/lib/librte_ring/meson.build
index a95598032..ca37cb8cc 100644
--- a/lib/librte_ring/meson.build
+++ b/lib/librte_ring/meson.build
@@ -7,6 +7,8 @@ headers = files('rte_ring.h',
 		'rte_ring_elem.h',
 		'rte_ring_c11_mem.h',
 		'rte_ring_generic.h',
+		'rte_ring_hts.h',
+		'rte_ring_hts_c11_mem.h',
 		'rte_ring_rts.h',
 		'rte_ring_rts_c11_mem.h')
 
diff --git a/lib/librte_ring/rte_ring.c b/lib/librte_ring/rte_ring.c
index 222eec0fb..ebe5ccf0d 100644
--- a/lib/librte_ring/rte_ring.c
+++ b/lib/librte_ring/rte_ring.c
@@ -89,9 +89,11 @@ static void
 reset_headtail(void *p)
 {
 	struct rte_ring_headtail *ht;
+	struct rte_ring_hts_headtail *ht_hts;
 	struct rte_ring_rts_headtail *ht_rts;
 
 	ht = p;
+	ht_hts = p;
 	ht_rts = p;
 
 	switch (ht->sync_type) {
@@ -104,6 +106,9 @@ reset_headtail(void *p)
 		ht_rts->head.raw = 0;
 		ht_rts->tail.raw = 0;
 		break;
+	case RTE_RING_SYNC_MT_HTS:
+		ht_hts->ht.raw = 0;
+		break;
 	default:
 		/* unknown sync mode */
 		RTE_ASSERT(0);
@@ -127,9 +132,9 @@ get_sync_type(uint32_t flags, enum rte_ring_sync_type *prod_st,
 	enum rte_ring_sync_type *cons_st)
 {
 	static const uint32_t prod_st_flags =
-		(RING_F_SP_ENQ | RING_F_MP_RTS_ENQ);
+		(RING_F_SP_ENQ | RING_F_MP_RTS_ENQ | RING_F_MP_HTS_ENQ);
 	static const uint32_t cons_st_flags =
-		(RING_F_SC_DEQ | RING_F_MC_RTS_DEQ);
+		(RING_F_SC_DEQ | RING_F_MC_RTS_DEQ | RING_F_MC_HTS_DEQ);
 
 	switch (flags & prod_st_flags) {
 	case 0:
@@ -141,6 +146,9 @@ get_sync_type(uint32_t flags, enum rte_ring_sync_type *prod_st,
 	case RING_F_MP_RTS_ENQ:
 		*prod_st = RTE_RING_SYNC_MT_RTS;
 		break;
+	case RING_F_MP_HTS_ENQ:
+		*prod_st = RTE_RING_SYNC_MT_HTS;
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -155,6 +163,9 @@ get_sync_type(uint32_t flags, enum rte_ring_sync_type *prod_st,
 	case RING_F_MC_RTS_DEQ:
 		*cons_st = RTE_RING_SYNC_MT_RTS;
 		break;
+	case RING_F_MC_HTS_DEQ:
+		*cons_st = RTE_RING_SYNC_MT_HTS;
+		break;
 	default:
 		return -EINVAL;
 	}
@@ -176,6 +187,11 @@ rte_ring_init(struct rte_ring *r, const char *name, unsigned count,
 	RTE_BUILD_BUG_ON((offsetof(struct rte_ring, prod) &
 			  RTE_CACHE_LINE_MASK) != 0);
 
+	RTE_BUILD_BUG_ON(offsetof(struct rte_ring_headtail, sync_type) !=
+		offsetof(struct rte_ring_hts_headtail, sync_type));
+	RTE_BUILD_BUG_ON(offsetof(struct rte_ring_headtail, tail) !=
+		offsetof(struct rte_ring_hts_headtail, ht.pos.tail));
+
 	RTE_BUILD_BUG_ON(offsetof(struct rte_ring_headtail, sync_type) !=
 		offsetof(struct rte_ring_rts_headtail, sync_type));
 	RTE_BUILD_BUG_ON(offsetof(struct rte_ring_headtail, tail) !=
diff --git a/lib/librte_ring/rte_ring.h b/lib/librte_ring/rte_ring.h
index 77f206ca7..7a7695914 100644
--- a/lib/librte_ring/rte_ring.h
+++ b/lib/librte_ring/rte_ring.h
@@ -398,6 +398,9 @@ rte_ring_enqueue_bulk(struct rte_ring *r, void * const *obj_table,
 	case RTE_RING_SYNC_MT_RTS:
 		return rte_ring_mp_rts_enqueue_bulk(r, obj_table, n,
 			free_space);
+	case RTE_RING_SYNC_MT_HTS:
+		return rte_ring_mp_hts_enqueue_bulk(r, obj_table, n,
+			free_space);
 #endif
 	}
 
@@ -545,6 +548,8 @@ rte_ring_dequeue_bulk(struct rte_ring *r, void **obj_table, unsigned int n,
 #ifdef ALLOW_EXPERIMENTAL_API
 	case RTE_RING_SYNC_MT_RTS:
 		return rte_ring_mc_rts_dequeue_bulk(r, obj_table, n, available);
+	case RTE_RING_SYNC_MT_HTS:
+		return rte_ring_mc_hts_dequeue_bulk(r, obj_table, n, available);
 #endif
 	}
 
@@ -879,6 +884,9 @@ rte_ring_enqueue_burst(struct rte_ring *r, void * const *obj_table,
 	case RTE_RING_SYNC_MT_RTS:
 		return rte_ring_mp_rts_enqueue_burst(r, obj_table, n,
 			free_space);
+	case RTE_RING_SYNC_MT_HTS:
+		return rte_ring_mp_hts_enqueue_burst(r, obj_table, n,
+			free_space);
 #endif
 	}
 
@@ -972,6 +980,9 @@ rte_ring_dequeue_burst(struct rte_ring *r, void **obj_table,
 	case RTE_RING_SYNC_MT_RTS:
 		return rte_ring_mc_rts_dequeue_burst(r, obj_table, n,
 			available);
+	case RTE_RING_SYNC_MT_HTS:
+		return rte_ring_mc_hts_dequeue_burst(r, obj_table, n,
+			available);
 #endif
 	}
 
diff --git a/lib/librte_ring/rte_ring_core.h b/lib/librte_ring/rte_ring_core.h
index 173b5f68d..450f2bc87 100644
--- a/lib/librte_ring/rte_ring_core.h
+++ b/lib/librte_ring/rte_ring_core.h
@@ -58,6 +58,7 @@ enum rte_ring_sync_type {
 	RTE_RING_SYNC_ST,     /**< single thread only */
 #ifdef ALLOW_EXPERIMENTAL_API
 	RTE_RING_SYNC_MT_RTS, /**< multi-thread relaxed tail sync */
+	RTE_RING_SYNC_MT_HTS, /**< multi-thread head/tail sync */
 #endif
 };
 
@@ -93,6 +94,19 @@ struct rte_ring_rts_headtail {
 	volatile union rte_ring_rts_poscnt head;
 };
 
+union rte_ring_hts_pos {
+	uint64_t raw;
+	struct {
+		uint32_t head; /**< head position */
+		uint32_t tail; /**< tail position */
+	} pos;
+};
+
+struct rte_ring_hts_headtail {
+	volatile union rte_ring_hts_pos ht;
+	enum rte_ring_sync_type sync_type;  /**< sync type of prod/cons */
+};
+
 /**
  * An RTE ring structure.
  *
@@ -124,6 +138,7 @@ struct rte_ring {
 	RTE_STD_C11
 	union {
 		struct rte_ring_headtail prod;
+		struct rte_ring_hts_headtail hts_prod;
 		struct rte_ring_rts_headtail rts_prod;
 	}  __rte_cache_aligned;
 
@@ -133,6 +148,7 @@ struct rte_ring {
 	RTE_STD_C11
 	union {
 		struct rte_ring_headtail cons;
+		struct rte_ring_hts_headtail hts_cons;
 		struct rte_ring_rts_headtail rts_cons;
 	}  __rte_cache_aligned;
 
@@ -155,6 +171,9 @@ struct rte_ring {
 #define RING_F_MP_RTS_ENQ 0x0008 /**< The default enqueue is "MP RTS". */
 #define RING_F_MC_RTS_DEQ 0x0010 /**< The default dequeue is "MC RTS". */
 
+#define RING_F_MP_HTS_ENQ 0x0020 /**< The default enqueue is "MP HTS". */
+#define RING_F_MC_HTS_DEQ 0x0040 /**< The default dequeue is "MC HTS". */
+
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/librte_ring/rte_ring_elem.h b/lib/librte_ring/rte_ring_elem.h
index 6da0a917b..df485fc6b 100644
--- a/lib/librte_ring/rte_ring_elem.h
+++ b/lib/librte_ring/rte_ring_elem.h
@@ -529,6 +529,7 @@ rte_ring_sp_enqueue_bulk_elem(struct rte_ring *r, const void *obj_table,
 }
 
 #ifdef ALLOW_EXPERIMENTAL_API
+#include <rte_ring_hts.h>
 #include <rte_ring_rts.h>
 #endif
 
@@ -573,6 +574,9 @@ rte_ring_enqueue_bulk_elem(struct rte_ring *r, const void *obj_table,
 	case RTE_RING_SYNC_MT_RTS:
 		return rte_ring_mp_rts_enqueue_bulk_elem(r, obj_table, esize, n,
 			free_space);
+	case RTE_RING_SYNC_MT_HTS:
+		return rte_ring_mp_hts_enqueue_bulk_elem(r, obj_table, esize, n,
+			free_space);
 #endif
 	}
 
@@ -754,6 +758,9 @@ rte_ring_dequeue_bulk_elem(struct rte_ring *r, void *obj_table,
 	case RTE_RING_SYNC_MT_RTS:
 		return rte_ring_mc_rts_dequeue_bulk_elem(r, obj_table, esize,
 			n, available);
+	case RTE_RING_SYNC_MT_HTS:
+		return rte_ring_mc_hts_dequeue_bulk_elem(r, obj_table, esize,
+			n, available);
 #endif
 	}
 
@@ -939,6 +946,9 @@ rte_ring_enqueue_burst_elem(struct rte_ring *r, const void *obj_table,
 	case RTE_RING_SYNC_MT_RTS:
 		return rte_ring_mp_rts_enqueue_burst_elem(r, obj_table, esize,
 			n, free_space);
+	case RTE_RING_SYNC_MT_HTS:
+		return rte_ring_mp_hts_enqueue_burst_elem(r, obj_table, esize,
+			n, free_space);
 #endif
 	}
 
@@ -1048,6 +1058,9 @@ rte_ring_dequeue_burst_elem(struct rte_ring *r, void *obj_table,
 	case RTE_RING_SYNC_MT_RTS:
 		return rte_ring_mc_rts_dequeue_burst_elem(r, obj_table, esize,
 			n, available);
+	case RTE_RING_SYNC_MT_HTS:
+		return rte_ring_mc_hts_dequeue_burst_elem(r, obj_table, esize,
+			n, available);
 #endif
 	}
 
diff --git a/lib/librte_ring/rte_ring_hts.h b/lib/librte_ring/rte_ring_hts.h
new file mode 100644
index 000000000..c7701defc
--- /dev/null
+++ b/lib/librte_ring/rte_ring_hts.h
@@ -0,0 +1,332 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (c) 2010-2020 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_HTS_H_
+#define _RTE_RING_HTS_H_
+
+/**
+ * @file rte_ring_hts.h
+ * @b EXPERIMENTAL: this API may change without prior notice
+ * It is not recommended to include this file directly.
+ * Please include <rte_ring.h> instead.
+ *
+ * Contains functions for serialized, aka Head-Tail Sync (HTS) ring mode.
+ * In that mode enqueue/dequeue operation is fully serialized:
+ * at any given moment only one enqueue/dequeue operation can proceed.
+ * This is achieved by allowing a thread to proceed with changing head.value
+ * only when head.value == tail.value.
+ * Both head and tail values are updated atomically (as one 64-bit value).
+ * To achieve that 64-bit CAS is used by head update routine.
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#include <rte_ring_hts_c11_mem.h>
+
+/**
+ * @internal Enqueue several objects on the HTS ring.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param obj_table
+ *   A pointer to a table of objects.
+ * @param esize
+ *   The size of ring element, in bytes. It must be a multiple of 4.
+ *   This must be the same value used while creating the ring. Otherwise
+ *   the results are undefined.
+ * @param n
+ *   The number of objects to add in the ring from the obj_table.
+ * @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 free_space
+ *   returns the amount of space after the enqueue operation has finished
+ * @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_do_hts_enqueue_elem(struct rte_ring *r, const void *obj_table,
+	uint32_t esize, uint32_t n, enum rte_ring_queue_behavior behavior,
+	uint32_t *free_space)
+{
+	uint32_t free, head;
+
+	n =  __rte_ring_hts_move_prod_head(r, n, behavior, &head, &free);
+
+	if (n != 0) {
+		__rte_ring_enqueue_elems(r, head, obj_table, esize, n);
+		__rte_ring_hts_update_tail(&r->hts_prod, head, n, 1);
+	}
+
+	if (free_space != NULL)
+		*free_space = free - n;
+	return n;
+}
+
+/**
+ * @internal Dequeue several objects from the HTS ring.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param obj_table
+ *   A pointer to a table of objects.
+ * @param esize
+ *   The size of ring element, in bytes. It must be a multiple of 4.
+ *   This must be the same value used while creating the ring. Otherwise
+ *   the results are undefined.
+ * @param n
+ *   The number of objects to pull from the ring.
+ * @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 available
+ *   returns the number of remaining ring entries after the dequeue has finished
+ * @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_do_hts_dequeue_elem(struct rte_ring *r, void *obj_table,
+	uint32_t esize, uint32_t n, enum rte_ring_queue_behavior behavior,
+	uint32_t *available)
+{
+	uint32_t entries, head;
+
+	n = __rte_ring_hts_move_cons_head(r, n, behavior, &head, &entries);
+
+	if (n != 0) {
+		__rte_ring_dequeue_elems(r, head, obj_table, esize, n);
+		__rte_ring_hts_update_tail(&r->hts_cons, head, n, 0);
+	}
+
+	if (available != NULL)
+		*available = entries - n;
+	return n;
+}
+
+/**
+ * Enqueue several objects on the HTS ring (multi-producers safe).
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param obj_table
+ *   A pointer to a table of objects.
+ * @param esize
+ *   The size of ring element, in bytes. It must be a multiple of 4.
+ *   This must be the same value used while creating the ring. Otherwise
+ *   the results are undefined.
+ * @param n
+ *   The number of objects to add in the ring from the obj_table.
+ * @param free_space
+ *   if non-NULL, returns the amount of space in the ring after the
+ *   enqueue operation has finished.
+ * @return
+ *   The number of objects enqueued, either 0 or n
+ */
+__rte_experimental
+static __rte_always_inline unsigned int
+rte_ring_mp_hts_enqueue_bulk_elem(struct rte_ring *r, const void *obj_table,
+	unsigned int esize, unsigned int n, unsigned int *free_space)
+{
+	return __rte_ring_do_hts_enqueue_elem(r, obj_table, esize, n,
+			RTE_RING_QUEUE_FIXED, free_space);
+}
+
+/**
+ * Dequeue several objects from an HTS ring (multi-consumers safe).
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param obj_table
+ *   A pointer to a table of objects that will be filled.
+ * @param esize
+ *   The size of ring element, in bytes. It must be a multiple of 4.
+ *   This must be the same value used while creating the ring. Otherwise
+ *   the results are undefined.
+ * @param n
+ *   The number of objects to dequeue from the ring to the obj_table.
+ * @param available
+ *   If non-NULL, returns the number of remaining ring entries after the
+ *   dequeue has finished.
+ * @return
+ *   The number of objects dequeued, either 0 or n
+ */
+__rte_experimental
+static __rte_always_inline unsigned int
+rte_ring_mc_hts_dequeue_bulk_elem(struct rte_ring *r, void *obj_table,
+	unsigned int esize, unsigned int n, unsigned int *available)
+{
+	return __rte_ring_do_hts_dequeue_elem(r, obj_table, esize, n,
+		RTE_RING_QUEUE_FIXED, available);
+}
+
+/**
+ * Enqueue several objects on the HTS ring (multi-producers safe).
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param obj_table
+ *   A pointer to a table of objects.
+ * @param esize
+ *   The size of ring element, in bytes. It must be a multiple of 4.
+ *   This must be the same value used while creating the ring. Otherwise
+ *   the results are undefined.
+ * @param n
+ *   The number of objects to add in the ring from the obj_table.
+ * @param free_space
+ *   if non-NULL, returns the amount of space in the ring after the
+ *   enqueue operation has finished.
+ * @return
+ *   - n: Actual number of objects enqueued.
+ */
+__rte_experimental
+static __rte_always_inline unsigned
+rte_ring_mp_hts_enqueue_burst_elem(struct rte_ring *r, const void *obj_table,
+	unsigned int esize, unsigned int n, unsigned int *free_space)
+{
+	return __rte_ring_do_hts_enqueue_elem(r, obj_table, esize, n,
+			RTE_RING_QUEUE_VARIABLE, free_space);
+}
+
+/**
+ * Dequeue several objects from an HTS  ring (multi-consumers safe).
+ * When the requested objects are more than the available objects,
+ * only dequeue the actual number of objects.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param obj_table
+ *   A pointer to a table of objects that will be filled.
+ * @param esize
+ *   The size of ring element, in bytes. It must be a multiple of 4.
+ *   This must be the same value used while creating the ring. Otherwise
+ *   the results are undefined.
+ * @param n
+ *   The number of objects to dequeue from the ring to the obj_table.
+ * @param available
+ *   If non-NULL, returns the number of remaining ring entries after the
+ *   dequeue has finished.
+ * @return
+ *   - n: Actual number of objects dequeued, 0 if ring is empty
+ */
+__rte_experimental
+static __rte_always_inline unsigned
+rte_ring_mc_hts_dequeue_burst_elem(struct rte_ring *r, void *obj_table,
+	unsigned int esize, unsigned int n, unsigned int *available)
+{
+	return __rte_ring_do_hts_dequeue_elem(r, obj_table, esize, n,
+			RTE_RING_QUEUE_VARIABLE, available);
+}
+
+/**
+ * Enqueue several objects on the HTS ring (multi-producers safe).
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param obj_table
+ *   A pointer to a table of void * pointers (objects).
+ * @param n
+ *   The number of objects to add in the ring from the obj_table.
+ * @param free_space
+ *   if non-NULL, returns the amount of space in the ring after the
+ *   enqueue operation has finished.
+ * @return
+ *   The number of objects enqueued, either 0 or n
+ */
+__rte_experimental
+static __rte_always_inline unsigned int
+rte_ring_mp_hts_enqueue_bulk(struct rte_ring *r, void * const *obj_table,
+			 unsigned int n, unsigned int *free_space)
+{
+	return rte_ring_mp_hts_enqueue_bulk_elem(r, obj_table,
+			sizeof(uintptr_t), n, free_space);
+}
+
+/**
+ * Dequeue several objects from an HTS ring (multi-consumers safe).
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param obj_table
+ *   A pointer to a table of void * pointers (objects) that will be filled.
+ * @param n
+ *   The number of objects to dequeue from the ring to the obj_table.
+ * @param available
+ *   If non-NULL, returns the number of remaining ring entries after the
+ *   dequeue has finished.
+ * @return
+ *   The number of objects dequeued, either 0 or n
+ */
+__rte_experimental
+static __rte_always_inline unsigned int
+rte_ring_mc_hts_dequeue_bulk(struct rte_ring *r, void **obj_table,
+		unsigned int n, unsigned int *available)
+{
+	return rte_ring_mc_hts_dequeue_bulk_elem(r, obj_table,
+			sizeof(uintptr_t), n, available);
+}
+
+/**
+ * Enqueue several objects on the HTS ring (multi-producers safe).
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param obj_table
+ *   A pointer to a table of void * pointers (objects).
+ * @param n
+ *   The number of objects to add in the ring from the obj_table.
+ * @param free_space
+ *   if non-NULL, returns the amount of space in the ring after the
+ *   enqueue operation has finished.
+ * @return
+ *   - n: Actual number of objects enqueued.
+ */
+__rte_experimental
+static __rte_always_inline unsigned
+rte_ring_mp_hts_enqueue_burst(struct rte_ring *r, void * const *obj_table,
+			 unsigned int n, unsigned int *free_space)
+{
+	return rte_ring_mp_hts_enqueue_burst_elem(r, obj_table,
+			sizeof(uintptr_t), n, free_space);
+}
+
+/**
+ * Dequeue several objects from an HTS  ring (multi-consumers safe).
+ * When the requested objects are more than the available objects,
+ * only dequeue the actual number of objects.
+ *
+ * @param r
+ *   A pointer to the ring structure.
+ * @param obj_table
+ *   A pointer to a table of void * pointers (objects) that will be filled.
+ * @param n
+ *   The number of objects to dequeue from the ring to the obj_table.
+ * @param available
+ *   If non-NULL, returns the number of remaining ring entries after the
+ *   dequeue has finished.
+ * @return
+ *   - n: Actual number of objects dequeued, 0 if ring is empty
+ */
+__rte_experimental
+static __rte_always_inline unsigned
+rte_ring_mc_hts_dequeue_burst(struct rte_ring *r, void **obj_table,
+		unsigned int n, unsigned int *available)
+{
+	return rte_ring_mc_hts_dequeue_burst_elem(r, obj_table,
+			sizeof(uintptr_t), n, available);
+}
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* _RTE_RING_HTS_H_ */
diff --git a/lib/librte_ring/rte_ring_hts_c11_mem.h b/lib/librte_ring/rte_ring_hts_c11_mem.h
new file mode 100644
index 000000000..87e84fdc9
--- /dev/null
+++ b/lib/librte_ring/rte_ring_hts_c11_mem.h
@@ -0,0 +1,207 @@
+/* SPDX-License-Identifier: BSD-3-Clause
+ *
+ * Copyright (c) 2010-2020 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_HTS_C11_MEM_H_
+#define _RTE_RING_HTS_C11_MEM_H_
+
+/**
+ * @file rte_ring_hts_c11_mem.h
+ * It is not recommended to include this file directly,
+ * include <rte_ring.h> instead.
+ * Contains internal helper functions for head/tail sync (HTS) ring mode.
+ * For more information please refer to <rte_ring_hts.h>.
+ */
+
+/**
+ * @internal get current tail value.
+ * Check that user didn't request to move tail above the head.
+ * In that situation:
+ * - return zero, that will cause abort any pending changes and
+ *   return head to its previous position.
+ * - throw an assert in debug mode.
+ */
+static __rte_always_inline uint32_t
+__rte_ring_hts_get_tail(struct rte_ring_hts_headtail *ht, uint32_t *tail,
+	uint32_t num)
+{
+	uint32_t n;
+	union rte_ring_hts_pos p;
+
+	p.raw = __atomic_load_n(&ht->ht.raw, __ATOMIC_RELAXED);
+	n = p.pos.head - p.pos.tail;
+
+	RTE_ASSERT(n >= num);
+	num = (n >= num) ? num : 0;
+
+	*tail = p.pos.tail;
+	return num;
+}
+
+/**
+ * @internal set new values for head and tail as one atomic 64 bit operation.
+ * Should be used only in conjunction with __rte_ring_hts_get_tail.
+ */
+static __rte_always_inline void
+__rte_ring_hts_set_head_tail(struct rte_ring_hts_headtail *ht, uint32_t tail,
+	uint32_t num, uint32_t enqueue)
+{
+	union rte_ring_hts_pos p;
+
+	RTE_SET_USED(enqueue);
+
+	p.pos.head = tail + num;
+	p.pos.tail = p.pos.head;
+
+	__atomic_store_n(&ht->ht.raw, p.raw, __ATOMIC_RELEASE);
+}
+
+/**
+ * @internal update tail with new value.
+ */
+static __rte_always_inline void
+__rte_ring_hts_update_tail(struct rte_ring_hts_headtail *ht, uint32_t old_tail,
+	uint32_t num, uint32_t enqueue)
+{
+	uint32_t tail;
+
+	RTE_SET_USED(enqueue);
+
+	tail = old_tail + num;
+	__atomic_store_n(&ht->ht.pos.tail, tail, __ATOMIC_RELEASE);
+}
+
+/**
+ * @internal waits till tail will become equal to head.
+ * Means no writer/reader is active for that ring.
+ * Suppose to work as serialization point.
+ */
+static __rte_always_inline void
+__rte_ring_hts_head_wait(const struct rte_ring_hts_headtail *ht,
+		union rte_ring_hts_pos *p)
+{
+	while (p->pos.head != p->pos.tail) {
+		rte_pause();
+		p->raw = __atomic_load_n(&ht->ht.raw, __ATOMIC_ACQUIRE);
+	}
+}
+
+/**
+ * @internal This function updates the producer head for enqueue
+ */
+static __rte_always_inline unsigned int
+__rte_ring_hts_move_prod_head(struct rte_ring *r, unsigned int num,
+	enum rte_ring_queue_behavior behavior, uint32_t *old_head,
+	uint32_t *free_entries)
+{
+	uint32_t n;
+	union rte_ring_hts_pos np, op;
+
+	const uint32_t capacity = r->capacity;
+
+	op.raw = __atomic_load_n(&r->hts_prod.ht.raw, __ATOMIC_ACQUIRE);
+
+	do {
+		/* Reset n to the initial burst count */
+		n = num;
+
+		/*
+		 * wait for tail to be equal to head,
+		 * make sure that we read prod head/tail *before*
+		 * reading cons tail.
+		 */
+		__rte_ring_hts_head_wait(&r->hts_prod, &op);
+
+		/*
+		 *  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 + r->cons.tail - op.pos.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)
+			break;
+
+		np.pos.tail = op.pos.tail;
+		np.pos.head = op.pos.head + n;
+
+	/*
+	 * this CAS(ACQUIRE, ACQUIRE) serves as a hoist barrier to prevent:
+	 *  - OOO reads of cons tail value
+	 *  - OOO copy of elems from the ring
+	 */
+	} while (__atomic_compare_exchange_n(&r->hts_prod.ht.raw,
+			&op.raw, np.raw,
+			0, __ATOMIC_ACQUIRE, __ATOMIC_ACQUIRE) == 0);
+
+	*old_head = op.pos.head;
+	return n;
+}
+
+/**
+ * @internal This function updates the consumer head for dequeue
+ */
+static __rte_always_inline unsigned int
+__rte_ring_hts_move_cons_head(struct rte_ring *r, unsigned int num,
+	enum rte_ring_queue_behavior behavior, uint32_t *old_head,
+	uint32_t *entries)
+{
+	uint32_t n;
+	union rte_ring_hts_pos np, op;
+
+	op.raw = __atomic_load_n(&r->hts_cons.ht.raw, __ATOMIC_ACQUIRE);
+
+	/* move cons.head atomically */
+	do {
+		/* Restore n as it may change every loop */
+		n = num;
+
+		/*
+		 * wait for tail to be equal to head,
+		 * make sure that we read cons head/tail *before*
+		 * reading prod tail.
+		 */
+		__rte_ring_hts_head_wait(&r->hts_cons, &op);
+
+		/* 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 = r->prod.tail - op.pos.head;
+
+		/* Set the actual entries for dequeue */
+		if (n > *entries)
+			n = (behavior == RTE_RING_QUEUE_FIXED) ? 0 : *entries;
+
+		if (unlikely(n == 0))
+			break;
+
+		np.pos.tail = op.pos.tail;
+		np.pos.head = op.pos.head + n;
+
+	/*
+	 * this CAS(ACQUIRE, ACQUIRE) serves as a hoist barrier to prevent:
+	 *  - OOO reads of prod tail value
+	 *  - OOO copy of elems from the ring
+	 */
+	} while (__atomic_compare_exchange_n(&r->hts_cons.ht.raw,
+			&op.raw, np.raw,
+			0, __ATOMIC_ACQUIRE, __ATOMIC_ACQUIRE) == 0);
+
+	*old_head = op.pos.head;
+	return n;
+}
+
+#endif /* _RTE_RING_HTS_C11_MEM_H_ */
