[dpdk-stable] patch 'hash: fix a multi-writer race condition' has been queued to stable release 18.05.1

[Christian Ehrhardt]

Hi,

FYI, your patch has been queued to stable release 18.05.1

Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet.
It will be pushed if I get no objections before 08/01/18. So please
shout if anyone has objections.

Thanks.

Christian Ehrhardt <christian.ehrhardt at canonical.com>

---
>From 2d95ec64b377cb47f6d63249e47c9c48dd888631 Mon Sep 17 00:00:00 2001
From: Yipeng Wang <yipeng1.wang at intel.com>
Date: Tue, 10 Jul 2018 09:59:55 -0700
Subject: [PATCH] hash: fix a multi-writer race condition

[ upstream commit eb067d431d9411a0054bc3ec084b0e9eadbb0a16 ]

Current multi-writer implementation uses Intel TSX to
protect the cuckoo path moving but not the cuckoo
path searching. After searching, we need to verify again if
the same empty slot still exists at the beginning of the TSX
region. Otherwise another writer could occupy the empty slot
before the TSX region. Current code does not verify.

Fixes: be856325cba3 ("hash: add scalable multi-writer insertion with Intel TSX")

Signed-off-by: Yipeng Wang <yipeng1.wang at intel.com>
Acked-by: Pablo de Lara <pablo.de.lara.guarch at intel.com>
---
 lib/librte_hash/rte_cuckoo_hash_x86.h | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/lib/librte_hash/rte_cuckoo_hash_x86.h b/lib/librte_hash/rte_cuckoo_hash_x86.h
index 2c5b017e3..981d7bdd6 100644
--- a/lib/librte_hash/rte_cuckoo_hash_x86.h
+++ b/lib/librte_hash/rte_cuckoo_hash_x86.h
@@ -66,6 +66,9 @@ rte_hash_cuckoo_move_insert_mw_tm(const struct rte_hash *h,
 	while (try < RTE_HASH_TSX_MAX_RETRY) {
 		status = rte_xbegin();
 		if (likely(status == RTE_XBEGIN_STARTED)) {
+			/* In case empty slot was gone before entering TSX */
+			if (curr_bkt->key_idx[curr_slot] != EMPTY_SLOT)
+				rte_xabort(RTE_XABORT_CUCKOO_PATH_INVALIDED);
 			while (likely(curr_node->prev != NULL)) {
 				prev_node = curr_node->prev;
 				prev_bkt = prev_node->bkt;
-- 
2.17.1