From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from dpdk.org (dpdk.org [92.243.14.124]) by dpdk.space (Postfix) with ESMTP id 01666A00E6 for ; Tue, 16 Apr 2019 16:39:11 +0200 (CEST) Received: from [92.243.14.124] (localhost [127.0.0.1]) by dpdk.org (Postfix) with ESMTP id E85E61B4D3; Tue, 16 Apr 2019 16:39:10 +0200 (CEST) Received: from mx1.redhat.com (mx1.redhat.com [209.132.183.28]) by dpdk.org (Postfix) with ESMTP id 647091B4E9 for ; Tue, 16 Apr 2019 16:39:09 +0200 (CEST) Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id C83DE30789BE; Tue, 16 Apr 2019 14:39:08 +0000 (UTC) Received: from rh.redhat.com (ovpn-117-214.ams2.redhat.com [10.36.117.214]) by smtp.corp.redhat.com (Postfix) with ESMTP id 5BF6D1001DE0; Tue, 16 Apr 2019 14:39:07 +0000 (UTC) From: Kevin Traynor To: Gavin Hu Cc: Ola Liljedahl , Nipun Gupta , Konstantin Ananyev , dpdk stable Date: Tue, 16 Apr 2019 15:37:13 +0100 Message-Id: <20190416143719.21601-55-ktraynor@redhat.com> In-Reply-To: <20190416143719.21601-1-ktraynor@redhat.com> References: <20190416143719.21601-1-ktraynor@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Tue, 16 Apr 2019 14:39:08 +0000 (UTC) Subject: [dpdk-stable] patch 'ring: enforce reading tail before slots' has been queued to LTS release 18.11.2 X-BeenThere: stable@dpdk.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: patches for DPDK stable branches List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: stable-bounces@dpdk.org Sender: "stable" Hi, FYI, your patch has been queued to LTS release 18.11.2 Note it hasn't been pushed to http://dpdk.org/browse/dpdk-stable yet. It will be pushed if I get no objections before 04/24/19. So please shout if anyone has objections. Also note that after the patch there's a diff of the upstream commit vs the patch applied to the branch. This will indicate if there was any rebasing needed to apply to the stable branch. If there were code changes for rebasing (ie: not only metadata diffs), please double check that the rebase was correctly done. Thanks. Kevin Traynor --- >From 76b5e7cde680dc9cacaaec01566d577422c32273 Mon Sep 17 00:00:00 2001 From: Gavin Hu Date: Wed, 13 Mar 2019 00:58:53 +0800 Subject: [PATCH] ring: enforce reading tail before slots [ upstream commit 85cffb2eccd9edf89a9e28539206a79258a6e9d9 ] In weak memory models, like arm64, reading the prod.tail may get reordered after reading the ring slots, which corrupts the ring and stale data is observed. This issue was reported by NXP on 8-A72 DPAA2 board. The problem is most likely caused by missing the acquire semantics when reading prod.tail (in SC dequeue) which makes it possible to read a stale value from the ring slots. For MP (and MC) case, rte_atomic32_cmpset() already provides the required ordering. For SP case, the control depependency between if-statement (which depends on the read of r->cons.tail) and the later stores to the ring slots make RMB unnecessary. About the control dependency, read more at: https://www.cl.cam.ac.uk/~pes20/ppc-supplemental/test7.pdf This patch is adding the required read barrier to prevent reading the ring slots get reordered before reading prod.tail for SC case. Fixes: c9fb3c62896f ("ring: move code in a new header file") Signed-off-by: Gavin Hu Reviewed-by: Ola Liljedahl Tested-by: Nipun Gupta Acked-by: Nipun Gupta Acked-by: Konstantin Ananyev --- lib/librte_ring/rte_ring_generic.h | 9 ++++++--- 1 file changed, 6 insertions(+), 3 deletions(-) diff --git a/lib/librte_ring/rte_ring_generic.h b/lib/librte_ring/rte_ring_generic.h index ea7dbe5b9..953cdbbd5 100644 --- a/lib/librte_ring/rte_ring_generic.h +++ b/lib/librte_ring/rte_ring_generic.h @@ -159,9 +159,12 @@ __rte_ring_move_cons_head(struct rte_ring *r, unsigned int is_sc, *new_head = *old_head + n; - if (is_sc) - r->cons.head = *new_head, success = 1; - else + if (is_sc) { + r->cons.head = *new_head; + rte_smp_rmb(); + success = 1; + } else { success = rte_atomic32_cmpset(&r->cons.head, *old_head, *new_head); + } } while (unlikely(success == 0)); return n; -- 2.20.1 --- Diff of the applied patch vs upstream commit (please double-check if non-empty: --- --- - 2019-04-16 15:34:27.649879139 +0100 +++ 0055-ring-enforce-reading-tail-before-slots.patch 2019-04-16 15:34:25.234178752 +0100 @@ -1,8 +1,10 @@ -From 85cffb2eccd9edf89a9e28539206a79258a6e9d9 Mon Sep 17 00:00:00 2001 +From 76b5e7cde680dc9cacaaec01566d577422c32273 Mon Sep 17 00:00:00 2001 From: Gavin Hu Date: Wed, 13 Mar 2019 00:58:53 +0800 Subject: [PATCH] ring: enforce reading tail before slots +[ upstream commit 85cffb2eccd9edf89a9e28539206a79258a6e9d9 ] + In weak memory models, like arm64, reading the prod.tail may get reordered after reading the ring slots, which corrupts the ring and stale data is observed. @@ -22,7 +24,6 @@ slots get reordered before reading prod.tail for SC case. Fixes: c9fb3c62896f ("ring: move code in a new header file") -Cc: stable@dpdk.org Signed-off-by: Gavin Hu Reviewed-by: Ola Liljedahl