[dpdk-dev] [PATCH v3 1/3] lib/lpm: integrate RCU QSBR

[Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>]

From: Ruifeng Wang <ruifeng.wang@arm.com>

Currently, the tbl8 group is freed even though the readers might be
using the tbl8 group entries. The freed tbl8 group can be reallocated
quickly. This results in incorrect lookup results.

RCU QSBR process is integrated for safe tbl8 group reclaim.
Refer to RCU documentation to understand various aspects of
integrating RCU library into other libraries.

Signed-off-by: Ruifeng Wang <ruifeng.wang@arm.com>
Reviewed-by: Honnappa Nagarahalli <honnappa.nagarahalli@arm.com>
---
 lib/librte_lpm/Makefile            |   3 +-
 lib/librte_lpm/meson.build         |   2 +
 lib/librte_lpm/rte_lpm.c           | 102 +++++++++++++++++++++++++----
 lib/librte_lpm/rte_lpm.h           |  21 ++++++
 lib/librte_lpm/rte_lpm_version.map |   6 ++
 5 files changed, 122 insertions(+), 12 deletions(-)

diff --git a/lib/librte_lpm/Makefile b/lib/librte_lpm/Makefile
index a7946a1c5..ca9e16312 100644
--- a/lib/librte_lpm/Makefile
+++ b/lib/librte_lpm/Makefile
@@ -6,9 +6,10 @@ include $(RTE_SDK)/mk/rte.vars.mk
 # library name
 LIB = librte_lpm.a
 
+CFLAGS += -DALLOW_EXPERIMENTAL_API
 CFLAGS += -O3
 CFLAGS += $(WERROR_FLAGS) -I$(SRCDIR)
-LDLIBS += -lrte_eal -lrte_hash
+LDLIBS += -lrte_eal -lrte_hash -lrte_rcu
 
 EXPORT_MAP := rte_lpm_version.map
 
diff --git a/lib/librte_lpm/meson.build b/lib/librte_lpm/meson.build
index a5176d8ae..19a35107f 100644
--- a/lib/librte_lpm/meson.build
+++ b/lib/librte_lpm/meson.build
@@ -2,9 +2,11 @@
 # Copyright(c) 2017 Intel Corporation
 
 version = 2
+allow_experimental_apis = true
 sources = files('rte_lpm.c', 'rte_lpm6.c')
 headers = files('rte_lpm.h', 'rte_lpm6.h')
 # since header files have different names, we can install all vector headers
 # without worrying about which architecture we actually need
 headers += files('rte_lpm_altivec.h', 'rte_lpm_neon.h', 'rte_lpm_sse.h')
 deps += ['hash']
+deps += ['rcu']
diff --git a/lib/librte_lpm/rte_lpm.c b/lib/librte_lpm/rte_lpm.c
index 3a929a1b1..ca58d4b35 100644
--- a/lib/librte_lpm/rte_lpm.c
+++ b/lib/librte_lpm/rte_lpm.c
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: BSD-3-Clause
  * Copyright(c) 2010-2014 Intel Corporation
+ * Copyright(c) 2019 Arm Limited
  */
 
 #include <string.h>
@@ -381,6 +382,8 @@ rte_lpm_free_v1604(struct rte_lpm *lpm)
 
 	rte_mcfg_tailq_write_unlock();
 
+	if (lpm->dq)
+		rte_rcu_qsbr_dq_delete(lpm->dq);
 	rte_free(lpm->tbl8);
 	rte_free(lpm->rules_tbl);
 	rte_free(lpm);
@@ -390,6 +393,59 @@ BIND_DEFAULT_SYMBOL(rte_lpm_free, _v1604, 16.04);
 MAP_STATIC_SYMBOL(void rte_lpm_free(struct rte_lpm *lpm),
 		rte_lpm_free_v1604);
 
+struct __rte_lpm_rcu_dq_entry {
+	uint32_t tbl8_group_index;
+	uint32_t pad;
+};
+
+static void
+__lpm_rcu_qsbr_free_resource(void *p, void *data)
+{
+	struct rte_lpm_tbl_entry zero_tbl8_entry = {0};
+	struct __rte_lpm_rcu_dq_entry *e =
+			(struct __rte_lpm_rcu_dq_entry *)data;
+	struct rte_lpm_tbl_entry *tbl8 = (struct rte_lpm_tbl_entry *)p;
+
+	/* Set tbl8 group invalid */
+	__atomic_store(&tbl8[e->tbl8_group_index], &zero_tbl8_entry,
+		__ATOMIC_RELAXED);
+}
+
+/* Associate QSBR variable with an LPM object.
+ */
+int
+rte_lpm_rcu_qsbr_add(struct rte_lpm *lpm, struct rte_rcu_qsbr *v)
+{
+	char rcu_dq_name[RTE_RCU_QSBR_DQ_NAMESIZE];
+	struct rte_rcu_qsbr_dq_parameters params;
+
+	if ((lpm == NULL) || (v == NULL)) {
+		rte_errno = EINVAL;
+		return 1;
+	}
+
+	if (lpm->dq) {
+		rte_errno = EEXIST;
+		return 1;
+	}
+
+	/* Init QSBR defer queue. */
+	snprintf(rcu_dq_name, sizeof(rcu_dq_name), "LPM_RCU_%s", lpm->name);
+	params.name = rcu_dq_name;
+	params.size = lpm->number_tbl8s;
+	params.esize = sizeof(struct __rte_lpm_rcu_dq_entry);
+	params.f = __lpm_rcu_qsbr_free_resource;
+	params.p = lpm->tbl8;
+	params.v = v;
+	lpm->dq = rte_rcu_qsbr_dq_create(&params);
+	if (lpm->dq == NULL) {
+		RTE_LOG(ERR, LPM, "LPM QS defer queue creation failed\n");
+		return 1;
+	}
+
+	return 0;
+}
+
 /*
  * Adds a rule to the rule table.
  *
@@ -679,14 +735,15 @@ tbl8_alloc_v20(struct rte_lpm_tbl_entry_v20 *tbl8)
 }
 
 static int32_t
-tbl8_alloc_v1604(struct rte_lpm_tbl_entry *tbl8, uint32_t number_tbl8s)
+__tbl8_alloc_v1604(struct rte_lpm *lpm)
 {
 	uint32_t group_idx; /* tbl8 group index. */
 	struct rte_lpm_tbl_entry *tbl8_entry;
 
 	/* Scan through tbl8 to find a free (i.e. INVALID) tbl8 group. */
-	for (group_idx = 0; group_idx < number_tbl8s; group_idx++) {
-		tbl8_entry = &tbl8[group_idx * RTE_LPM_TBL8_GROUP_NUM_ENTRIES];
+	for (group_idx = 0; group_idx < lpm->number_tbl8s; group_idx++) {
+		tbl8_entry = &lpm->tbl8[group_idx *
+					RTE_LPM_TBL8_GROUP_NUM_ENTRIES];
 		/* If a free tbl8 group is found clean it and set as VALID. */
 		if (!tbl8_entry->valid_group) {
 			struct rte_lpm_tbl_entry new_tbl8_entry = {
@@ -712,6 +769,21 @@ tbl8_alloc_v1604(struct rte_lpm_tbl_entry *tbl8, uint32_t number_tbl8s)
 	return -ENOSPC;
 }
 
+static int32_t
+tbl8_alloc_v1604(struct rte_lpm *lpm)
+{
+	int32_t group_idx; /* tbl8 group index. */
+
+	group_idx = __tbl8_alloc_v1604(lpm);
+	if ((group_idx < 0) && (lpm->dq != NULL)) {
+		/* If there are no tbl8 groups try to reclaim some. */
+		if (rte_rcu_qsbr_dq_reclaim(lpm->dq) == 0)
+			group_idx = __tbl8_alloc_v1604(lpm);
+	}
+
+	return group_idx;
+}
+
 static void
 tbl8_free_v20(struct rte_lpm_tbl_entry_v20 *tbl8, uint32_t tbl8_group_start)
 {
@@ -728,13 +800,21 @@ tbl8_free_v20(struct rte_lpm_tbl_entry_v20 *tbl8, uint32_t tbl8_group_start)
 }
 
 static void
-tbl8_free_v1604(struct rte_lpm_tbl_entry *tbl8, uint32_t tbl8_group_start)
+tbl8_free_v1604(struct rte_lpm *lpm, uint32_t tbl8_group_start)
 {
-	/* Set tbl8 group invalid*/
 	struct rte_lpm_tbl_entry zero_tbl8_entry = {0};
+	struct __rte_lpm_rcu_dq_entry e;
 
-	__atomic_store(&tbl8[tbl8_group_start], &zero_tbl8_entry,
-			__ATOMIC_RELAXED);
+	if (lpm->dq != NULL) {
+		e.tbl8_group_index = tbl8_group_start;
+		e.pad = 0;
+		/* Push into QSBR defer queue. */
+		rte_rcu_qsbr_dq_enqueue(lpm->dq, (void *)&e);
+	} else {
+		/* Set tbl8 group invalid*/
+		__atomic_store(&lpm->tbl8[tbl8_group_start], &zero_tbl8_entry,
+				__ATOMIC_RELAXED);
+	}
 }
 
 static __rte_noinline int32_t
@@ -1037,7 +1117,7 @@ add_depth_big_v1604(struct rte_lpm *lpm, uint32_t ip_masked, uint8_t depth,
 
 	if (!lpm->tbl24[tbl24_index].valid) {
 		/* Search for a free tbl8 group. */
-		tbl8_group_index = tbl8_alloc_v1604(lpm->tbl8, lpm->number_tbl8s);
+		tbl8_group_index = tbl8_alloc_v1604(lpm);
 
 		/* Check tbl8 allocation was successful. */
 		if (tbl8_group_index < 0) {
@@ -1083,7 +1163,7 @@ add_depth_big_v1604(struct rte_lpm *lpm, uint32_t ip_masked, uint8_t depth,
 	} /* If valid entry but not extended calculate the index into Table8. */
 	else if (lpm->tbl24[tbl24_index].valid_group == 0) {
 		/* Search for free tbl8 group. */
-		tbl8_group_index = tbl8_alloc_v1604(lpm->tbl8, lpm->number_tbl8s);
+		tbl8_group_index = tbl8_alloc_v1604(lpm);
 
 		if (tbl8_group_index < 0) {
 			return tbl8_group_index;
@@ -1818,7 +1898,7 @@ delete_depth_big_v1604(struct rte_lpm *lpm, uint32_t ip_masked,
 		 */
 		lpm->tbl24[tbl24_index].valid = 0;
 		__atomic_thread_fence(__ATOMIC_RELEASE);
-		tbl8_free_v1604(lpm->tbl8, tbl8_group_start);
+		tbl8_free_v1604(lpm, tbl8_group_start);
 	} else if (tbl8_recycle_index > -1) {
 		/* Update tbl24 entry. */
 		struct rte_lpm_tbl_entry new_tbl24_entry = {
@@ -1834,7 +1914,7 @@ delete_depth_big_v1604(struct rte_lpm *lpm, uint32_t ip_masked,
 		__atomic_store(&lpm->tbl24[tbl24_index], &new_tbl24_entry,
 				__ATOMIC_RELAXED);
 		__atomic_thread_fence(__ATOMIC_RELEASE);
-		tbl8_free_v1604(lpm->tbl8, tbl8_group_start);
+		tbl8_free_v1604(lpm, tbl8_group_start);
 	}
 #undef group_idx
 	return 0;
diff --git a/lib/librte_lpm/rte_lpm.h b/lib/librte_lpm/rte_lpm.h
index 906ec4483..49c12a68d 100644
--- a/lib/librte_lpm/rte_lpm.h
+++ b/lib/librte_lpm/rte_lpm.h
@@ -1,5 +1,6 @@
 /* SPDX-License-Identifier: BSD-3-Clause
  * Copyright(c) 2010-2014 Intel Corporation
+ * Copyright(c) 2019 Arm Limited
  */
 
 #ifndef _RTE_LPM_H_
@@ -21,6 +22,7 @@
 #include <rte_common.h>
 #include <rte_vect.h>
 #include <rte_compat.h>
+#include <rte_rcu_qsbr.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -186,6 +188,7 @@ struct rte_lpm {
 			__rte_cache_aligned; /**< LPM tbl24 table. */
 	struct rte_lpm_tbl_entry *tbl8; /**< LPM tbl8 table. */
 	struct rte_lpm_rule *rules_tbl; /**< LPM rules. */
+	struct rte_rcu_qsbr_dq *dq;	/**< RCU QSBR defer queue.*/
 };
 
 /**
@@ -248,6 +251,24 @@ rte_lpm_free_v20(struct rte_lpm_v20 *lpm);
 void
 rte_lpm_free_v1604(struct rte_lpm *lpm);
 
+/**
+ * Associate RCU QSBR variable with an LPM object.
+ *
+ * @param lpm
+ *   the lpm object to add RCU QSBR
+ * @param v
+ *   RCU QSBR variable
+ * @return
+ *   On success - 0
+ *   On error - 1 with error code set in rte_errno.
+ *   Possible rte_errno codes are:
+ *   - EINVAL - invalid pointer
+ *   - EEXIST - already added QSBR
+ *   - ENOMEM - memory allocation failure
+ */
+__rte_experimental
+int rte_lpm_rcu_qsbr_add(struct rte_lpm *lpm, struct rte_rcu_qsbr *v);
+
 /**
  * Add a rule to the LPM table.
  *
diff --git a/lib/librte_lpm/rte_lpm_version.map b/lib/librte_lpm/rte_lpm_version.map
index 90beac853..b353aabd2 100644
--- a/lib/librte_lpm/rte_lpm_version.map
+++ b/lib/librte_lpm/rte_lpm_version.map
@@ -44,3 +44,9 @@ DPDK_17.05 {
 	rte_lpm6_lookup_bulk_func;
 
 } DPDK_16.04;
+
+EXPERIMENTAL {
+	global:
+
+	rte_lpm_rcu_qsbr_add;
+};
-- 
2.17.1