When a tbl8 group is getting attached to a tbl24 entry, lookup
might fail even though the entry is configured in the table.
For ex: consider a LPM table configured with 10.10.10.1/24.
When a new entry 10.10.10.32/28 is being added, a new tbl8
group is allocated and tbl24 entry is changed to point to
the tbl8 group. If the tbl24 entry is written without the tbl8
group entries updated, a lookup on 10.10.10.9 will return
failure.
Correct memory orderings are required to ensure that the
store to tbl24 does not happen before the stores to tbl8 group
entries complete.
Signed-off-by: Honnappa Nagarahalli <honnappa.nagaraha...@arm.com>
Signed-off-by: Ruifeng Wang <ruifeng.w...@arm.com>
Reviewed-by: Gavin Hu <gavin...@arm.com>
---
lib/librte_lpm/rte_lpm.c | 32 +++++++++++++++++++++++++-------
lib/librte_lpm/rte_lpm.h | 4 ++++
2 files changed, 29 insertions(+), 7 deletions(-)
diff --git a/lib/librte_lpm/rte_lpm.c b/lib/librte_lpm/rte_lpm.c
index 18efa496c..396ad94e2 100644
--- a/lib/librte_lpm/rte_lpm.c
+++ b/lib/librte_lpm/rte_lpm.c
@@ -806,7 +806,8 @@ add_depth_small_v1604(struct rte_lpm *lpm, uint32_t ip,
uint8_t depth,
/* Setting tbl24 entry in one go to avoid race
* conditions
*/
- lpm->tbl24[i] = new_tbl24_entry;
+ __atomic_store(&lpm->tbl24[i], &new_tbl24_entry,
+ __ATOMIC_RELEASE);
continue;
}
@@ -1017,7 +1018,11 @@ add_depth_big_v1604(struct rte_lpm *lpm, uint32_t
ip_masked, uint8_t depth,
.depth = 0,
};
- lpm->tbl24[tbl24_index] = new_tbl24_entry;
+ /* The tbl24 entry must be written only after the
+ * tbl8 entries are written.
+ */
+ __atomic_store(&lpm->tbl24[tbl24_index], &new_tbl24_entry,
+ __ATOMIC_RELEASE);
} /* If valid entry but not extended calculate the index into Table8. */
else if (lpm->tbl24[tbl24_index].valid_group == 0) {
@@ -1063,7 +1068,11 @@ add_depth_big_v1604(struct rte_lpm *lpm, uint32_t
ip_masked, uint8_t depth,
.depth = 0,
};
- lpm->tbl24[tbl24_index] = new_tbl24_entry;
+ /* The tbl24 entry must be written only after the
+ * tbl8 entries are written.
+ */
+ __atomic_store(&lpm->tbl24[tbl24_index], &new_tbl24_entry,
+ __ATOMIC_RELEASE);
} else { /*
* If it is valid, extended entry calculate the index into tbl8.
@@ -1391,6 +1400,7 @@ delete_depth_small_v1604(struct rte_lpm *lpm, uint32_t
ip_masked,
/* Calculate the range and index into Table24. */
tbl24_range = depth_to_range(depth);
tbl24_index = (ip_masked >> 8);
+ struct rte_lpm_tbl_entry zero_tbl24_entry = {0};
/*
* Firstly check the sub_rule_index. A -1 indicates no replacement rule
@@ -1405,7 +1415,8 @@ delete_depth_small_v1604(struct rte_lpm *lpm, uint32_t
ip_masked,
if (lpm->tbl24[i].valid_group == 0 &&
lpm->tbl24[i].depth <= depth) {
- lpm->tbl24[i].valid = INVALID;
+ __atomic_store(&lpm->tbl24[i],
+ &zero_tbl24_entry, __ATOMIC_RELEASE);
} else if (lpm->tbl24[i].valid_group == 1) {
/*
* If TBL24 entry is extended, then there has
@@ -1450,7 +1461,8 @@ delete_depth_small_v1604(struct rte_lpm *lpm, uint32_t
ip_masked,
if (lpm->tbl24[i].valid_group == 0 &&
lpm->tbl24[i].depth <= depth) {
- lpm->tbl24[i] = new_tbl24_entry;
+ __atomic_store(&lpm->tbl24[i], &new_tbl24_entry,
+ __ATOMIC_RELEASE);
} else if (lpm->tbl24[i].valid_group == 1) {
/*
* If TBL24 entry is extended, then there has
@@ -1713,8 +1725,11 @@ delete_depth_big_v1604(struct rte_lpm *lpm, uint32_t
ip_masked,
tbl8_recycle_index = tbl8_recycle_check_v1604(lpm->tbl8,
tbl8_group_start);
if (tbl8_recycle_index == -EINVAL) {
- /* Set tbl24 before freeing tbl8 to avoid race condition. */
+ /* Set tbl24 before freeing tbl8 to avoid race condition.
+ * Prevent the free of the tbl8 group from hoisting.
+ */
lpm->tbl24[tbl24_index].valid = 0;
+ __atomic_thread_fence(__ATOMIC_RELEASE);
tbl8_free_v1604(lpm->tbl8, tbl8_group_start);
} else if (tbl8_recycle_index > -1) {
/* Update tbl24 entry. */
@@ -1725,8 +1740,11 @@ delete_depth_big_v1604(struct rte_lpm *lpm, uint32_t
ip_masked,
.depth = lpm->tbl8[tbl8_recycle_index].depth,
};
- /* Set tbl24 before freeing tbl8 to avoid race condition. */
+ /* Set tbl24 before freeing tbl8 to avoid race condition.
+ * Prevent the free of the tbl8 group from hoisting.
+ */
lpm->tbl24[tbl24_index] = new_tbl24_entry;
+ __atomic_thread_fence(__ATOMIC_RELEASE);
tbl8_free_v1604(lpm->tbl8, tbl8_group_start);
}
#undef group_idx
diff --git a/lib/librte_lpm/rte_lpm.h b/lib/librte_lpm/rte_lpm.h
index b886f54b4..6f5704c5c 100644
--- a/lib/librte_lpm/rte_lpm.h
+++ b/lib/librte_lpm/rte_lpm.h
@@ -354,6 +354,10 @@ rte_lpm_lookup(struct rte_lpm *lpm, uint32_t ip, uint32_t
*next_hop)
ptbl = (const uint32_t *)(&lpm->tbl24[tbl24_index]);
tbl_entry = *ptbl;
+ /* Memory ordering is not required in lookup. Because dataflow
+ * dependency exists, compiler or HW won't be able to re-order
+ * the operations.
+ */
/* Copy tbl8 entry (only if needed) */
if (unlikely((tbl_entry & RTE_LPM_VALID_EXT_ENTRY_BITMASK) ==
RTE_LPM_VALID_EXT_ENTRY_BITMASK)) {
--
2.17.1
