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From: Steven Lariau <steven.lariau@arm.com>
To: Gage Eads <gage.eads@intel.com>, Olivier Matz <olivier.matz@6wind.com>
Cc: dev@dpdk.org, nd@arm.com, Steven Lariau <steven.lariau@arm.com>
Subject: [dpdk-dev] [PATCH v2 2/5] lib/stack: remove push acquire fence
Date: Fri, 25 Sep 2020 18:43:36 +0100
Message-ID: <20200925174340.10014-3-steven.lariau@arm.com> (raw)
In-Reply-To: <20200925174340.10014-1-steven.lariau@arm.com>

An acquire fence is used to make sure loads after the fence can observe
all store operations before a specific store-release.
But push doesn't read any data, except for the head which is part of a
CAS operation (the items on the list are not read).
So there is no need for the acquire barrier.

Signed-off-by: Steven Lariau <steven.lariau@arm.com>
Reviewed-by: Dharmik Thakkar <dharmik.thakkar@arm.com>
Reviewed-by: Ruifeng Wang <ruifeng.wang@arm.com>
Acked-by: Gage Eads <gage.eads@intel.com>
---
 lib/librte_stack/rte_stack_lf_c11.h | 6 ------
 1 file changed, 6 deletions(-)

diff --git a/lib/librte_stack/rte_stack_lf_c11.h b/lib/librte_stack/rte_stack_lf_c11.h
index 1e0ea0bef..82b7287f1 100644
--- a/lib/librte_stack/rte_stack_lf_c11.h
+++ b/lib/librte_stack/rte_stack_lf_c11.h
@@ -44,12 +44,6 @@ __rte_stack_lf_push_elems(struct rte_stack_lf_list *list,
 	do {
 		struct rte_stack_lf_head new_head;
 
-		/* Use an acquire fence to establish a synchronized-with
-		 * relationship between the list->head load and store-release
-		 * operations (as part of the rte_atomic128_cmp_exchange()).
-		 */
-		__atomic_thread_fence(__ATOMIC_ACQUIRE);
-
 		/* Swing the top pointer to the first element in the list and
 		 * make the last element point to the old top.
 		 */
-- 
2.17.1


  parent reply	other threads:[~2020-09-25 17:44 UTC|newest]

Thread overview: 22+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-11 15:29 [dpdk-dev] [PATCH 0/5] lib/stack: improve lockfree C11 implementation Steven Lariau
2020-09-11 15:29 ` [dpdk-dev] [PATCH 1/5] lib/stack: fix inconsistent weak / strong cas Steven Lariau
2020-09-21 17:16   ` Eads, Gage
2020-09-11 15:29 ` [dpdk-dev] [PATCH 2/5] lib/stack: remove push acquire fence Steven Lariau
2020-09-21 17:16   ` Eads, Gage
2020-09-11 15:29 ` [dpdk-dev] [PATCH 3/5] lib/stack: remove redundant orderings for list->len Steven Lariau
2020-09-21 17:16   ` Eads, Gage
2020-09-11 15:29 ` [dpdk-dev] [PATCH 4/5] lib/stack: reload head when pop fails Steven Lariau
2020-09-21 17:16   ` Eads, Gage
2020-09-11 15:29 ` [dpdk-dev] [PATCH 5/5] lib/stack: remove pop cas release ordering Steven Lariau
2020-09-21 17:17   ` Eads, Gage
2020-09-25 14:27     ` David Marchand
2020-09-25 17:43 ` [dpdk-dev] [PATCH v2 0/5] lib/stack: improve lockfree C11 implementation Steven Lariau
2020-09-25 17:43   ` [dpdk-dev] [PATCH v2 1/5] lib/stack: fix inconsistent weak / strong cas Steven Lariau
2020-09-28 10:22     ` David Marchand
2020-09-28 15:58       ` Eads, Gage
2020-09-25 17:43   ` Steven Lariau [this message]
2020-09-25 17:43   ` [dpdk-dev] [PATCH v2 3/5] lib/stack: remove redundant orderings for list->len Steven Lariau
2020-09-25 17:43   ` [dpdk-dev] [PATCH v2 4/5] lib/stack: reload head when pop fails Steven Lariau
2020-09-25 17:43   ` [dpdk-dev] [PATCH v2 5/5] lib/stack: remove pop cas release ordering Steven Lariau
2020-09-25 17:57     ` Eads, Gage
2020-09-30 19:14   ` [dpdk-dev] [PATCH v2 0/5] lib/stack: improve lockfree C11 implementation David Marchand

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