{"id":810723,"url":"http://patchwork.ozlabs.org/api/patches/810723/?format=json","web_url":"http://patchwork.ozlabs.org/project/netdev/patch/20170906163551.20387-1-Haakon.Bugge@oracle.com/","project":{"id":7,"url":"http://patchwork.ozlabs.org/api/projects/7/?format=json","name":"Linux network development","link_name":"netdev","list_id":"netdev.vger.kernel.org","list_email":"netdev@vger.kernel.org","web_url":null,"scm_url":null,"webscm_url":null,"list_archive_url":"","list_archive_url_format":"","commit_url_format":""},"msgid":"<20170906163551.20387-1-Haakon.Bugge@oracle.com>","list_archive_url":null,"date":"2017-09-06T16:35:51","name":"[net,v2] rds: Fix incorrect statistics counting","commit_ref":null,"pull_url":null,"state":"accepted","archived":true,"hash":"bd6a5949c1403c96d30b655661e327b5a382fdb3","submitter":{"id":72009,"url":"http://patchwork.ozlabs.org/api/people/72009/?format=json","name":"Haakon Bugge","email":"Haakon.Bugge@oracle.com"},"delegate":{"id":34,"url":"http://patchwork.ozlabs.org/api/users/34/?format=json","username":"davem","first_name":"David","last_name":"Miller","email":"davem@davemloft.net"},"mbox":"http://patchwork.ozlabs.org/project/netdev/patch/20170906163551.20387-1-Haakon.Bugge@oracle.com/mbox/","series":[{"id":1850,"url":"http://patchwork.ozlabs.org/api/series/1850/?format=json","web_url":"http://patchwork.ozlabs.org/project/netdev/list/?series=1850","date":"2017-09-06T16:35:51","name":"[net,v2] rds: Fix incorrect statistics counting","version":2,"mbox":"http://patchwork.ozlabs.org/series/1850/mbox/"}],"comments":"http://patchwork.ozlabs.org/api/patches/810723/comments/","check":"pending","checks":"http://patchwork.ozlabs.org/api/patches/810723/checks/","tags":{},"related":[],"headers":{"Return-Path":"","X-Original-To":"patchwork-incoming@ozlabs.org","Delivered-To":"patchwork-incoming@ozlabs.org","Authentication-Results":"ozlabs.org;\n\tspf=none (mailfrom) smtp.mailfrom=vger.kernel.org\n\t(client-ip=209.132.180.67; helo=vger.kernel.org;\n\tenvelope-from=netdev-owner@vger.kernel.org;\n\treceiver=)","Received":["from vger.kernel.org (vger.kernel.org [209.132.180.67])\n\tby ozlabs.org (Postfix) with ESMTP id 3xnTks46bNz9t2R\n\tfor ;\n\tThu, 7 Sep 2017 02:37:09 +1000 (AEST)","(majordomo@vger.kernel.org) by vger.kernel.org via listexpand\n\tid S1755471AbdIFQgo (ORCPT );\n\tWed, 6 Sep 2017 12:36:44 -0400","from aserp1040.oracle.com ([141.146.126.69]:34630 \"EHLO\n\taserp1040.oracle.com\" rhost-flags-OK-OK-OK-OK) by vger.kernel.org\n\twith ESMTP id S1753775AbdIFQgm (ORCPT\n\t); Wed, 6 Sep 2017 12:36:42 -0400","from userv0022.oracle.com (userv0022.oracle.com [156.151.31.74])\n\tby aserp1040.oracle.com (Sentrion-MTA-4.3.2/Sentrion-MTA-4.3.2) with\n\tESMTP id v86Ga4Ka002281\n\t(version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256\n\tverify=OK); Wed, 6 Sep 2017 16:36:05 GMT","from userv0122.oracle.com (userv0122.oracle.com [156.151.31.75])\n\tby userv0022.oracle.com (8.14.4/8.14.4) with ESMTP id v86Ga3VX023269\n\t(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256\n\tverify=OK); Wed, 6 Sep 2017 16:36:03 GMT","from abhmp0011.oracle.com (abhmp0011.oracle.com [141.146.116.17])\n\tby userv0122.oracle.com (8.14.4/8.14.4) with ESMTP id\n\tv86Ga3f0013258; Wed, 6 Sep 2017 16:36:03 GMT","from lab02.no.oracle.com (/10.172.144.56)\n\tby default (Oracle Beehive Gateway v4.0)\n\twith ESMTP ; Wed, 06 Sep 2017 09:36:02 -0700"],"From":"=?utf-8?q?H=C3=A5kon_Bugge?= ","To":"Santosh Shilimkar ,\n\t\"David S . Miller\" ","Cc":"netdev@vger.kernel.org, linux-rdma@vger.kernel.org,\n\trds-devel@oss.oracle.com, linux-kernel@vger.kernel.org,\n\tknut.omang@oracle.com","Subject":"[PATCH net v2] rds: Fix incorrect statistics counting","Date":"Wed, 6 Sep 2017 18:35:51 +0200","Message-Id":"<20170906163551.20387-1-Haakon.Bugge@oracle.com>","X-Mailer":"git-send-email 2.9.3","MIME-Version":"1.0","Content-Type":"text/plain; charset=UTF-8","Content-Transfer-Encoding":"8bit","X-Source-IP":"userv0022.oracle.com [156.151.31.74]","Sender":"netdev-owner@vger.kernel.org","Precedence":"bulk","List-ID":"","X-Mailing-List":"netdev@vger.kernel.org"},"content":"In rds_send_xmit() there is logic to batch the sends. However, if\nanother thread has acquired the lock and has incremented the send_gen,\nit is considered a race and we yield. The code incrementing the\ns_send_lock_queue_raced statistics counter did not count this event\ncorrectly.\n\nThis commit counts the race condition correctly.\n\nChanges from v1:\n- Removed check for *someone_on_xmit()*\n- Fixed incorrect indentation\n\nSigned-off-by: Håkon Bugge \nReviewed-by: Knut Omang \n---\n net/rds/send.c | 10 +++++++---\n 1 file changed, 7 insertions(+), 3 deletions(-)","diff":"diff --git a/net/rds/send.c b/net/rds/send.c\nindex 058a407..b52cdc8 100644\n--- a/net/rds/send.c\n+++ b/net/rds/send.c\n@@ -428,14 +428,18 @@ int rds_send_xmit(struct rds_conn_path *cp)\n \t * some work and we will skip our goto\n \t */\n \tif (ret == 0) {\n+\t\tbool raced;\n+\n \t\tsmp_mb();\n+\t\traced = send_gen != READ_ONCE(cp->cp_send_gen);\n+\n \t\tif ((test_bit(0, &conn->c_map_queued) ||\n-\t\t !list_empty(&cp->cp_send_queue)) &&\n-\t\t\tsend_gen == READ_ONCE(cp->cp_send_gen)) {\n-\t\t\trds_stats_inc(s_send_lock_queue_raced);\n+\t\t !list_empty(&cp->cp_send_queue)) && !raced) {\n \t\t\tif (batch_count < send_batch_count)\n \t\t\t\tgoto restart;\n \t\t\tqueue_delayed_work(rds_wq, &cp->cp_send_w, 1);\n+\t\t} else if (raced) {\n+\t\t\trds_stats_inc(s_send_lock_queue_raced);\n \t\t}\n \t}\n out:\n","prefixes":["net","v2"]}