<snip>
>
> > Add resource reclamation APIs to make it simple for applications and
> > libraries to integrate rte_rcu library.
>
> Few nits, thoughts, please see below.
> Apart from that - LGTM.
> Acked-by: Konstantin Ananyev <konstantin.anan...@intel.com>
>
> >
> > Signed-off-by: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
> > Reviewed-by: Ola Liljedhal <ola.liljed...@arm.com>
> > Reviewed-by: Ruifeng Wang <ruifeng.w...@arm.com>
> > ---
> > lib/librte_rcu/Makefile | 2 +-
> > lib/librte_rcu/meson.build | 2 +
> > lib/librte_rcu/rcu_qsbr_pvt.h | 57 +++++++
> > lib/librte_rcu/rte_rcu_qsbr.c | 243 ++++++++++++++++++++++++++++-
> > lib/librte_rcu/rte_rcu_qsbr.h | 188 ++++++++++++++++++++++
> > lib/librte_rcu/rte_rcu_version.map | 4 +
> > lib/meson.build | 6 +-
> > 7 files changed, 498 insertions(+), 4 deletions(-) create mode
> > 100644 lib/librte_rcu/rcu_qsbr_pvt.h
> >
> > diff --git a/lib/librte_rcu/Makefile b/lib/librte_rcu/Makefile index
> > c4bb28d77..95f8a57e2 100644
> > --- a/lib/librte_rcu/Makefile
> > +++ b/lib/librte_rcu/Makefile
> > @@ -8,7 +8,7 @@ LIB = librte_rcu.a
> >
> > CFLAGS += -DALLOW_EXPERIMENTAL_API
> > CFLAGS += $(WERROR_FLAGS) -I$(SRCDIR) -O3 -LDLIBS += -lrte_eal
> > +LDLIBS += -lrte_eal -lrte_ring
> >
> > EXPORT_MAP := rte_rcu_version.map
> >
> > diff --git a/lib/librte_rcu/meson.build b/lib/librte_rcu/meson.build
> > index 62920ba02..e280b29c1 100644
> > --- a/lib/librte_rcu/meson.build
> > +++ b/lib/librte_rcu/meson.build
> > @@ -10,3 +10,5 @@ headers = files('rte_rcu_qsbr.h') if cc.get_id() ==
> > 'clang' and dpdk_conf.get('RTE_ARCH_64') == false
> > ext_deps += cc.find_library('atomic') endif
> > +
> > +deps += ['ring']
> > diff --git a/lib/librte_rcu/rcu_qsbr_pvt.h
> > b/lib/librte_rcu/rcu_qsbr_pvt.h new file mode 100644 index
> > 000000000..413f28587
> > --- /dev/null
> > +++ b/lib/librte_rcu/rcu_qsbr_pvt.h
> > @@ -0,0 +1,57 @@
> > +/* SPDX-License-Identifier: BSD-3-Clause
> > + * Copyright (c) 2019 Arm Limited
> > + */
> > +
> > +#ifndef _RTE_RCU_QSBR_PVT_H_
> > +#define _RTE_RCU_QSBR_PVT_H_
> > +
> > +/**
> > + * This file is private to the RCU library. It should not be included
> > + * by the user of this library.
> > + */
> > +
> > +#ifdef __cplusplus
> > +extern "C" {
> > +#endif
> > +
> > +#include <rte_ring.h>
> > +#include <rte_ring_elem.h>
> > +
> > +#include "rte_rcu_qsbr.h"
> > +
> > +/* RTE defer queue structure.
> > + * This structure holds the defer queue. The defer queue is used to
> > + * hold the deleted entries from the data structure that are not
> > + * yet freed.
> > + */
> > +struct rte_rcu_qsbr_dq {
> > + struct rte_rcu_qsbr *v; /**< RCU QSBR variable used by this queue.*/
> > + struct rte_ring *r; /**< RCU QSBR defer queue. */
> > + uint32_t size;
> > + /**< Number of elements in the defer queue */
> > + uint32_t esize;
> > + /**< Size (in bytes) of data, including the token, stored on the
> > + * defer queue.
> > + */
> > + uint32_t trigger_reclaim_limit;
> > + /**< Trigger automatic reclamation after the defer queue
> > + * has atleast these many resources waiting.
> > + */
> > + uint32_t max_reclaim_size;
> > + /**< Reclaim at the max these many resources during auto
> > + * reclamation.
> > + */
> > + rte_rcu_qsbr_free_resource_t free_fn;
> > + /**< Function to call to free the resource. */
> > + void *p;
> > + /**< Pointer passed to the free function. Typically, this is the
> > + * pointer to the data structure to which the resource to free
> > + * belongs.
> > + */
> > +};
> > +
> > +#ifdef __cplusplus
> > +}
> > +#endif
> > +
> > +#endif /* _RTE_RCU_QSBR_PVT_H_ */
> > diff --git a/lib/librte_rcu/rte_rcu_qsbr.c
> > b/lib/librte_rcu/rte_rcu_qsbr.c index 2f3fad776..e8c1e386f 100644
> > --- a/lib/librte_rcu/rte_rcu_qsbr.c
> > +++ b/lib/librte_rcu/rte_rcu_qsbr.c
> > @@ -1,6 +1,6 @@
> > /* SPDX-License-Identifier: BSD-3-Clause
> > *
> > - * Copyright (c) 2018 Arm Limited
> > + * Copyright (c) 2018-2019 Arm Limited
> > */
> >
> > #include <stdio.h>
> > @@ -18,8 +18,10 @@
> > #include <rte_per_lcore.h>
> > #include <rte_lcore.h>
> > #include <rte_errno.h>
> > +#include <rte_ring_elem.h>
> >
> > #include "rte_rcu_qsbr.h"
> > +#include "rcu_qsbr_pvt.h"
> >
> > /* Get the memory size of QSBR variable */ size_t @@ -270,6 +272,245
> > @@ rte_rcu_qsbr_dump(FILE *f, struct rte_rcu_qsbr *v)
> > return 0;
> > }
> >
> > +/* Create a queue used to store the data structure elements that can
> > + * be freed later. This queue is referred to as 'defer queue'.
> > + */
> > +struct rte_rcu_qsbr_dq *
> > +rte_rcu_qsbr_dq_create(const struct rte_rcu_qsbr_dq_parameters
> > +*params) {
> > + struct rte_rcu_qsbr_dq *dq;
> > + uint32_t qs_fifo_size;
> > + unsigned int flags;
> > +
> > + if (params == NULL || params->free_fn == NULL ||
> > + params->v == NULL || params->name == NULL ||
> > + params->size == 0 || params->esize == 0 ||
> > + (params->esize % 4 != 0)) {
> > + rte_log(RTE_LOG_ERR, rte_rcu_log_type,
> > + "%s(): Invalid input parameter\n", __func__);
> > + rte_errno = EINVAL;
> > +
> > + return NULL;
> > + }
> > + /* If auto reclamation is configured, reclaim limit
> > + * should be a valid value.
> > + */
> > + if ((params->trigger_reclaim_limit <= params->size) &&
> > + (params->max_reclaim_size == 0)) {
> > + rte_log(RTE_LOG_ERR, rte_rcu_log_type,
> > + "%s(): Invalid input parameter, size = %u,
> trigger_reclaim_limit = %u, max_reclaim_size = %u\n",
> > + __func__, params->size, params-
> >trigger_reclaim_limit,
> > + params->max_reclaim_size);
> > + rte_errno = EINVAL;
> > +
> > + return NULL;
> > + }
> > +
> > + dq = rte_zmalloc(NULL, sizeof(struct rte_rcu_qsbr_dq),
> > + RTE_CACHE_LINE_SIZE);
> > + if (dq == NULL) {
> > + rte_errno = ENOMEM;
> > +
> > + return NULL;
> > + }
> > +
> > + /* Decide the flags for the ring.
> > + * If MT safety is requested, use RTS for ring enqueue as most
> > + * use cases involve dq-enqueue happening on the control plane.
> > + * Ring dequeue is always HTS due to the possibility of revert.
> > + */
> > + flags = RING_F_MP_RTS_ENQ;
> > + if (params->flags & RTE_RCU_QSBR_DQ_MT_UNSAFE)
> > + flags = RING_F_SP_ENQ;
> > + flags |= RING_F_MC_HTS_DEQ;
> > + /* round up qs_fifo_size to next power of two that is not less than
> > + * max_size.
> > + */
> > + qs_fifo_size = rte_align32pow2(params->size + 1);
> > + /* Add token size to ring element size */
> > + dq->r = rte_ring_create_elem(params->name,
> > + __RTE_QSBR_TOKEN_SIZE + params->esize,
> > + qs_fifo_size, SOCKET_ID_ANY, flags);
> > + if (dq->r == NULL) {
> > + rte_log(RTE_LOG_ERR, rte_rcu_log_type,
> > + "%s(): defer queue create failed\n", __func__);
> > + rte_free(dq);
> > + return NULL;
> > + }
> > +
> > + dq->v = params->v;
> > + dq->size = params->size;
> > + dq->esize = __RTE_QSBR_TOKEN_SIZE + params->esize;
> > + dq->trigger_reclaim_limit = params->trigger_reclaim_limit;
> > + dq->max_reclaim_size = params->max_reclaim_size;
> > + dq->free_fn = params->free_fn;
> > + dq->p = params->p;
> > +
> > + return dq;
> > +}
> > +
> > +/* Enqueue one resource to the defer queue to free after the grace
> > + * period is over.
> > + */
> > +int rte_rcu_qsbr_dq_enqueue(struct rte_rcu_qsbr_dq *dq, void *e) {
> > + uint64_t token;
> > + uint32_t cur_size, free_size;
> > +
> > + if (dq == NULL || e == NULL) {
> > + rte_log(RTE_LOG_ERR, rte_rcu_log_type,
> > + "%s(): Invalid input parameter\n", __func__);
> > + rte_errno = EINVAL;
> > +
> > + return 1;
> > + }
> > +
> > + /* Start the grace period */
> > + token = rte_rcu_qsbr_start(dq->v);
> > +
> > + /* Reclaim resources if the queue is 1/8th full. This helps
>
> Comment about 1/8 is probably left from older version?
> As I understand now it is configurable parameter.
Ack, will correct this.
>
> > + * the queue from growing too large and allows time for reader
> > + * threads to report their quiescent state.
> > + */
> > + cur_size = rte_ring_count(dq->r);
> > + if (cur_size > dq->trigger_reclaim_limit) {
> > + rte_log(RTE_LOG_INFO, rte_rcu_log_type,
> > + "%s(): Triggering reclamation\n", __func__);
> > + rte_rcu_qsbr_dq_reclaim(dq, dq->max_reclaim_size, NULL,
> NULL);
> > + }
> > +
> > + /* Check if there is space for atleast 1 resource */
> > + free_size = rte_ring_free_count(dq->r);
> > + if (!free_size) {
>
> Is there any point to do this check at all?
> You are doing enqueue below and handle situation with not enough space in
> the ring anyway.
Ack
>
> > + rte_log(RTE_LOG_ERR, rte_rcu_log_type,
> > + "%s(): Defer queue is full\n", __func__);
> > + /* Note that the token generated above is not used.
> > + * Other than wasting tokens, it should not cause any
> > + * other issues.
> > + */
> > + rte_log(RTE_LOG_INFO, rte_rcu_log_type,
> > + "%s(): Skipped enqueuing token = %"PRIu64"\n",
> > + __func__, token);
> > +
> > + rte_errno = ENOSPC;
> > + return 1;
> > + }
> > +
> > + /* Enqueue the token and resource. Generating the token
> > + * and enqueuing (token + resource) on the queue is not an
> > + * atomic operation. This might result in tokens enqueued
> > + * out of order on the queue. So, some tokens might wait
> > + * longer than they are required to be reclaimed.
> > + */
> > + char data[dq->esize];
> > + memcpy(data, &token, __RTE_QSBR_TOKEN_SIZE);
> > + memcpy(data + __RTE_QSBR_TOKEN_SIZE, e,
> > + dq->esize - __RTE_QSBR_TOKEN_SIZE);
> > + /* Check the status as enqueue might fail since the other thread
> > + * might have used up the freed space.
> > + * Enqueue uses the configured flags when the DQ was created.
> > + */
> > + if (rte_ring_enqueue_elem(dq->r, data, dq->esize) != 0) {
> > + rte_log(RTE_LOG_ERR, rte_rcu_log_type,
> > + "%s(): Enqueue failed\n", __func__);
> > + /* Note that the token generated above is not used.
> > + * Other than wasting tokens, it should not cause any
> > + * other issues.
> > + */
> > + rte_log(RTE_LOG_INFO, rte_rcu_log_type,
> > + "%s(): Skipped enqueuing token = %"PRIu64"\n",
> > + __func__, token);
> > +
> > + rte_errno = ENOSPC;
> > + return 1;
> > + }
>
>
> Just as a thought: in theory if we'll use MP_HTS(/SP) ring we can avoid
> wasting RCU tokens:
>
> if (rte_ring_enqueue_elem_bulk_start(dq->r, 1, NULL) != 0) {
> token = rte_rcu_qsbr_start(dq->v);
> memcpy(data, &token, __RTE_QSBR_TOKEN_SIZE);
> rte_ring_enqueue_elem_finish(dq->r, data, dq->esize, 1); }
>
> Though it might slowdown things if we'll have a lot of parallel dq_enqueue.
> So not sure is it worth it or not.
Adding peek APIs for RTS would be better. That should take care of the parallel
dw_enqueue. Not sure if I gave you the comment. My ring patch supported these
APIs.
>
> > +
> > + rte_log(RTE_LOG_INFO, rte_rcu_log_type,
> > + "%s(): Enqueued token = %"PRIu64"\n", __func__, token);
> > +
> > + return 0;
> > +}
> > +
> > +/* Reclaim resources from the defer queue. */ int
> > +rte_rcu_qsbr_dq_reclaim(struct rte_rcu_qsbr_dq *dq, unsigned int n,
> > + unsigned int *freed, unsigned int *pending) {
> > + uint32_t cnt;
> > + uint64_t token;
> > +
> > + if (dq == NULL || n == 0) {
> > + rte_log(RTE_LOG_ERR, rte_rcu_log_type,
> > + "%s(): Invalid input parameter\n", __func__);
> > + rte_errno = EINVAL;
> > +
> > + return 1;
> > + }
> > +
> > + cnt = 0;
> > +
> > + char e[dq->esize];
> > + /* Check reader threads quiescent state and reclaim resources */
> > + while ((cnt < n) &&
> > + (rte_ring_dequeue_bulk_elem_start(dq->r, e,
> > + dq->esize, 1, NULL) != 0)) {
>
> Another thought - any point to use burst_elem_start() here to retrieve more
> then 1 elem in one go? Something like:
I think it makes sense.
> char e[32][dq->size];
> while ((cnt < n) {
> k = RTE_MAX(32, cnt - n);
> k = rte_ring_dequeue_burst_elem_start(dq->r, e, dq->esize, k, NULL);
> if (k = 0)
> break;
> for (i = 0; i != k; i++) {
> memcpy(&token, e[i], sizeof(uint64_t));
> if (rte_rcu_qsbr_check(dq->v, token, false) != 1)
> break;
> }
> k = i;
> rte_ring_dequeue_elem_finish(dq->r, k);
> for (i = 0; i != k; i++)
> dq->free_fn(dq->p, e[i] + __RTE_QSBR_TOKEN_SIZE);
I think it also makes sense to change the free_fn to take 'n' number of tokens.
> n += k;
> if (k == 0)
> break;
>
> ?
> Also if at enqueue we guarantee strict ordrer (via
> enqueue_start/enqueue_finish), then here we probably can do _check_ from
> the last retrieved token here?
> In theory that might help to minimize number of checks.
> I.E. do:
> for (i = k; i-- !=0; ) {
> memcpy(&token, e[i], sizeof(uint64_t));
> if (rte_rcu_qsbr_check(dq->v, token, false) != 1)
There is a higher chance that later tokens are not acked. This introduces more
polling of the counters.
The rte_rcu_qsbr_check has an optimization. While acking the current token, it
will also caches the greatest token acked. It uses the cached token for the
subsequent calls. I think this provides a better optimization.
> break;
> }
> k = i + 1;
> ...
>
> > + memcpy(&token, e, sizeof(uint64_t));
> > +
> > + /* Reclaim the resource */
> > + if (rte_rcu_qsbr_check(dq->v, token, false) != 1) {
> > + rte_ring_dequeue_finish(dq->r, 0);
> > + break;
> > + }
> > + rte_ring_dequeue_finish(dq->r, 1);
> > +
> > + rte_log(RTE_LOG_INFO, rte_rcu_log_type,
> > + "%s(): Reclaimed token = %"PRIu64"\n",
> > + __func__, *(uint64_t *)e);
> > +
> > + dq->free_fn(dq->p, e + __RTE_QSBR_TOKEN_SIZE);
> > +
> > + cnt++;
> > + }
> > +
> > + rte_log(RTE_LOG_INFO, rte_rcu_log_type,
> > + "%s(): Reclaimed %u resources\n", __func__, cnt);
> > +
> > + if (freed != NULL)
> > + *freed = cnt;
> > + if (pending != NULL)
> > + *pending = rte_ring_count(dq->r);
> > +
> > + return 0;
> > +}
> > +
> > +/* Delete a defer queue. */
> > +int
> > +rte_rcu_qsbr_dq_delete(struct rte_rcu_qsbr_dq *dq) {
> > + unsigned int pending;
> > +
> > + if (dq == NULL) {
> > + rte_log(RTE_LOG_ERR, rte_rcu_log_type,
> > + "%s(): Invalid input parameter\n", __func__);
> > + rte_errno = EINVAL;
> > +
> > + return 1;
> > + }
> > +
> > + /* Reclaim all the resources */
> > + rte_rcu_qsbr_dq_reclaim(dq, ~0, NULL, &pending);
> > + if (pending != 0) {
> > + rte_errno = EAGAIN;
> > +
> > + return 1;
> > + }
> > +
> > + rte_ring_free(dq->r);
> > + rte_free(dq);
> > +
> > + return 0;
> > +}
> > +
> > int rte_rcu_log_type;
> >
> > RTE_INIT(rte_rcu_register)
> > diff --git a/lib/librte_rcu/rte_rcu_qsbr.h
> > b/lib/librte_rcu/rte_rcu_qsbr.h index 0b5585925..213f9b029 100644
> > --- a/lib/librte_rcu/rte_rcu_qsbr.h
> > +++ b/lib/librte_rcu/rte_rcu_qsbr.h
> > @@ -34,6 +34,7 @@ extern "C" {
> > #include <rte_lcore.h>
> > #include <rte_debug.h>
> > #include <rte_atomic.h>
> > +#include <rte_ring.h>
> >
> > extern int rte_rcu_log_type;
> >
> > @@ -84,6 +85,7 @@ struct rte_rcu_qsbr_cnt { #define
> > __RTE_QSBR_CNT_THR_OFFLINE 0 #define __RTE_QSBR_CNT_INIT 1
> #define
> > __RTE_QSBR_CNT_MAX ((uint64_t)~0)
> > +#define __RTE_QSBR_TOKEN_SIZE sizeof(uint64_t)
> >
> > /* RTE Quiescent State variable structure.
> > * This structure has two elements that vary in size based on the @@
> > -114,6 +116,84 @@ struct rte_rcu_qsbr {
> > */
> > } __rte_cache_aligned;
> >
> > +/**
> > + * Call back function called to free the resources.
> > + *
> > + * @param p
> > + * Pointer provided while creating the defer queue
> > + * @param e
> > + * Pointer to the resource data stored on the defer queue
> > + *
> > + * @return
> > + * None
> > + */
> > +typedef void (*rte_rcu_qsbr_free_resource_t)(void *p, void *e);
> > +
> > +#define RTE_RCU_QSBR_DQ_NAMESIZE RTE_RING_NAMESIZE
> > +
> > +/**
> > + * Various flags supported.
> > + */
> > +/**< Enqueue and reclaim operations are multi-thread safe by default.
> > + * The call back functions registered to free the resources are
> > + * assumed to be multi-thread safe.
> > + * Set this flag is multi-thread safety is not required.
> > + */
> > +#define RTE_RCU_QSBR_DQ_MT_UNSAFE 1
> > +
> > +/**
> > + * Parameters used when creating the defer queue.
> > + */
> > +struct rte_rcu_qsbr_dq_parameters {
> > + const char *name;
> > + /**< Name of the queue. */
> > + uint32_t flags;
> > + /**< Flags to control API behaviors */
> > + uint32_t size;
> > + /**< Number of entries in queue. Typically, this will be
> > + * the same as the maximum number of entries supported in the
> > + * lock free data structure.
> > + * Data structures with unbounded number of entries is not
> > + * supported currently.
> > + */
> > + uint32_t esize;
> > + /**< Size (in bytes) of each element in the defer queue.
> > + * This has to be multiple of 4B.
> > + */
> > + uint32_t trigger_reclaim_limit;
> > + /**< Trigger automatic reclamation after the defer queue
> > + * has atleast these many resources waiting. This auto
> > + * reclamation is triggered in rte_rcu_qsbr_dq_enqueue API
> > + * call.
> > + * If this is greater than 'size', auto reclamation is
> > + * not triggered.
> > + * If this is set to 0, auto reclamation is triggered
> > + * in every call to rte_rcu_qsbr_dq_enqueue API.
> > + */
> > + uint32_t max_reclaim_size;
> > + /**< When automatic reclamation is enabled, reclaim at the max
> > + * these many resources. This should contain a valid value, if
> > + * auto reclamation is on. Setting this to 'size' or greater will
> > + * reclaim all possible resources currently on the defer queue.
> > + */
> > + rte_rcu_qsbr_free_resource_t free_fn;
> > + /**< Function to call to free the resource. */
> > + void *p;
> > + /**< Pointer passed to the free function. Typically, this is the
> > + * pointer to the data structure to which the resource to free
> > + * belongs. This can be NULL.
> > + */
> > + struct rte_rcu_qsbr *v;
> > + /**< RCU QSBR variable to use for this defer queue */ };
> > +
> > +/* RTE defer queue structure.
> > + * This structure holds the defer queue. The defer queue is used to
> > + * hold the deleted entries from the data structure that are not
> > + * yet freed.
> > + */
> > +struct rte_rcu_qsbr_dq;
> > +
> > /**
> > * @warning
> > * @b EXPERIMENTAL: this API may change without prior notice @@
> > -692,6 +772,114 @@ __rte_experimental int rte_rcu_qsbr_dump(FILE *f,
> > struct rte_rcu_qsbr *v);
> >
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this API may change without prior notice
> > + *
> > + * Create a queue used to store the data structure elements that can
> > + * be freed later. This queue is referred to as 'defer queue'.
> > + *
> > + * @param params
> > + * Parameters to create a defer queue.
> > + * @return
> > + * On success - Valid pointer to defer queue
> > + * On error - NULL
> > + * Possible rte_errno codes are:
> > + * - EINVAL - NULL parameters are passed
> > + * - ENOMEM - Not enough memory
> > + */
> > +__rte_experimental
> > +struct rte_rcu_qsbr_dq *
> > +rte_rcu_qsbr_dq_create(const struct rte_rcu_qsbr_dq_parameters
> > +*params);
> > +
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this API may change without prior notice
> > + *
> > + * Enqueue one resource to the defer queue and start the grace period.
> > + * The resource will be freed later after at least one grace period
> > + * is over.
> > + *
> > + * If the defer queue is full, it will attempt to reclaim resources.
> > + * It will also reclaim resources at regular intervals to avoid
> > + * the defer queue from growing too big.
> > + *
> > + * Multi-thread safety is provided as the defer queue configuration.
> > + * When multi-thread safety is requested, it is possible that the
> > + * resources are not stored in their order of deletion. This results
> > + * in resources being held in the defer queue longer than they should.
> > + *
> > + * @param dq
> > + * Defer queue to allocate an entry from.
> > + * @param e
> > + * Pointer to resource data to copy to the defer queue. The size of
> > + * the data to copy is equal to the element size provided when the
> > + * defer queue was created.
> > + * @return
> > + * On success - 0
> > + * On error - 1 with rte_errno set to
> > + * - EINVAL - NULL parameters are passed
> > + * - ENOSPC - Defer queue is full. This condition can not happen
> > + * if the defer queue size is equal (or larger) than the
> > + * number of elements in the data structure.
> > + */
> > +__rte_experimental
> > +int
> > +rte_rcu_qsbr_dq_enqueue(struct rte_rcu_qsbr_dq *dq, void *e);
> > +
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this API may change without prior notice
> > + *
> > + * Free quesed resources from the defer queue.
> > + *
> > + * This API is multi-thread safe.
> > + *
> > + * @param dq
> > + * Defer queue to free an entry from.
> > + * @param n
> > + * Maximum number of resources to free.
> > + * @param freed
> > + * Number of resources that were freed.
> > + * @param pending
> > + * Number of resources pending on the defer queue. This number might
> not
> > + * be acurate if multi-thread safety is configured.
> > + * @return
> > + * On successful reclamation of at least 1 resource - 0
> > + * On error - 1 with rte_errno set to
> > + * - EINVAL - NULL parameters are passed
> > + */
> > +__rte_experimental
> > +int
> > +rte_rcu_qsbr_dq_reclaim(struct rte_rcu_qsbr_dq *dq, unsigned int n,
> > + unsigned int *freed, unsigned int *pending);
> > +
> > +/**
> > + * @warning
> > + * @b EXPERIMENTAL: this API may change without prior notice
> > + *
> > + * Delete a defer queue.
> > + *
> > + * It tries to reclaim all the resources on the defer queue.
> > + * If any of the resources have not completed the grace period
> > + * the reclamation stops and returns immediately. The rest of
> > + * the resources are not reclaimed and the defer queue is not
> > + * freed.
> > + *
> > + * @param dq
> > + * Defer queue to delete.
> > + * @return
> > + * On success - 0
> > + * On error - 1
> > + * Possible rte_errno codes are:
> > + * - EINVAL - NULL parameters are passed
> > + * - EAGAIN - Some of the resources have not completed at least 1 grace
> > + * period, try again.
> > + */
> > +__rte_experimental
> > +int
> > +rte_rcu_qsbr_dq_delete(struct rte_rcu_qsbr_dq *dq);
> > +
> > #ifdef __cplusplus
> > }
> > #endif
> > diff --git a/lib/librte_rcu/rte_rcu_version.map
> > b/lib/librte_rcu/rte_rcu_version.map
> > index f8b9ef2ab..dfac88a37 100644
> > --- a/lib/librte_rcu/rte_rcu_version.map
> > +++ b/lib/librte_rcu/rte_rcu_version.map
> > @@ -8,6 +8,10 @@ EXPERIMENTAL {
> > rte_rcu_qsbr_synchronize;
> > rte_rcu_qsbr_thread_register;
> > rte_rcu_qsbr_thread_unregister;
> > + rte_rcu_qsbr_dq_create;
> > + rte_rcu_qsbr_dq_enqueue;
> > + rte_rcu_qsbr_dq_reclaim;
> > + rte_rcu_qsbr_dq_delete;
> >
> > local: *;
> > };
> > diff --git a/lib/meson.build b/lib/meson.build index
> > 9c3cc55d5..15e91a303 100644
> > --- a/lib/meson.build
> > +++ b/lib/meson.build
> > @@ -11,7 +11,9 @@
> > libraries = [
> > 'kvargs', # eal depends on kvargs
> > 'eal', # everything depends on eal
> > - 'ring', 'mempool', 'mbuf', 'net', 'meter', 'ethdev', 'pci', # core
> > + 'ring',
> > + 'rcu', # rcu depends on ring
> > + 'mempool', 'mbuf', 'net', 'meter', 'ethdev', 'pci', # core
> > 'cmdline',
> > 'metrics', # bitrate/latency stats depends on this
> > 'hash', # efd depends on this
> > @@ -22,7 +24,7 @@ libraries = [
> > 'gro', 'gso', 'ip_frag', 'jobstats',
> > 'kni', 'latencystats', 'lpm', 'member',
> > 'power', 'pdump', 'rawdev',
> > - 'rcu', 'rib', 'reorder', 'sched', 'security', 'stack', 'vhost',
> > + 'rib', 'reorder', 'sched', 'security', 'stack', 'vhost',
> > # ipsec lib depends on net, crypto and security
> > 'ipsec',
> > #fib lib depends on rib
> > --
> > 2.17.1
