From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.1 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6A399C3A5A7 for ; Fri, 30 Aug 2019 09:32:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 3E5CC23429 for ; Fri, 30 Aug 2019 09:32:38 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="bqFBGWBr" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728067AbfH3Jch (ORCPT ); Fri, 30 Aug 2019 05:32:37 -0400 Received: from mail-wr1-f65.google.com ([209.85.221.65]:34876 "EHLO mail-wr1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727236AbfH3Jcg (ORCPT ); Fri, 30 Aug 2019 05:32:36 -0400 Received: by mail-wr1-f65.google.com with SMTP id g7so6283713wrx.2 for ; Fri, 30 Aug 2019 02:32:35 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=subject:to:references:from:message-id:date:user-agent:mime-version :in-reply-to:content-language:content-transfer-encoding; bh=+47wD5vGZ+6kUib765nKfUpzmQhNcuWkVLIbcOTw29M=; b=bqFBGWBroRmmRKcvZzKsu+g8bCZm7qIJT5Tuw2T1n9ZxS6FjtvQtLoUIvPovOYoyMF zm0of0+kMSbdGYKpoP8/2qgZ5yEG4bInmhHM+nvWFjJCg1LyMgHt4XtTYza6t2320e/o IR6bb5komWIxHXq2y8KK082STfGWAb9IpExH6Esfy7a8QcU0j+40LpRwxUm3HR7v9Nbi joWLHAHF3xX3BbI1T3HETn9t6i98WSn/9Ays+EEHRSAsk2OlR3r787CkPiLXhAS/yMyZ bZ+Pt4LZrUXw+0VBw/OVF3XulmeJ8nlH5P4PeG5Q+FSdGkGJ49MeV7fVJ2ppQxRjwRQq jPMg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:subject:to:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-language :content-transfer-encoding; bh=+47wD5vGZ+6kUib765nKfUpzmQhNcuWkVLIbcOTw29M=; b=D1FpFssXszUbbbTn7XNTBxCPwrWy9bLThss+2geIlPogdMZAkJO+8PN0a5fJ4Yh3KW 6gX+6eUVLwVvrHiAwKF9E6H6HNIHEBDuzHOK7N9Xk3+oJsr8J16KWkm8ryckoXlUybwq pe/ac7TI/qWnqmWX/YhEc3pBuAUvBKxBbYAEt37T/h3vpH/SxXJbIKGh7JmpEsAAjGv2 DB3Cc27dsnG4HunQrUhShrDiTalFWeKfCjbjFyihsnpqPg1znVC3qblHNwa2TFPrZ59W WxMSGx60Qw0jaU1U4jcriZVuH4S1X5IQuR3BiUwUNtOiJIOMhmc1dmNR6L2T5DQRGNrz 8NOw== X-Gm-Message-State: APjAAAXto62E+TZqtKO25ElL0lQbtHkPusfBCDoMZGCjTo2SOxJZUHKx 2Iw38hrNb5b3PgFsAH7djhI= X-Google-Smtp-Source: APXvYqwaZPU8RDZo27OAx9VActHGrUB7ZmFn5Ouo/BXN0qrtdp8kGW2B40Z+R2RY/zsGsgCaWMn8fQ== X-Received: by 2002:a5d:51c6:: with SMTP id n6mr1036003wrv.206.1567157554852; Fri, 30 Aug 2019 02:32:34 -0700 (PDT) Received: from [192.168.8.147] (31.169.185.81.rev.sfr.net. [81.185.169.31]) by smtp.gmail.com with ESMTPSA id a142sm6903516wme.2.2019.08.30.02.32.33 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 30 Aug 2019 02:32:34 -0700 (PDT) Subject: Re: [PATCH 1/1] forcedeth: use per cpu to collect xmit/recv statistics To: Zhu Yanjun , netdev@vger.kernel.org, davem@davemloft.net, nan.1986san@gmail.com References: <1567154111-23315-1-git-send-email-yanjun.zhu@oracle.com> <1567154111-23315-2-git-send-email-yanjun.zhu@oracle.com> From: Eric Dumazet Message-ID: <24ad8394-cb24-fcb7-0dc2-3435429bb8cd@gmail.com> Date: Fri, 30 Aug 2019 11:32:33 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <1567154111-23315-2-git-send-email-yanjun.zhu@oracle.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 8/30/19 10:35 AM, Zhu Yanjun wrote: > When testing with a background iperf pushing 1Gbit/sec traffic and running > both ifconfig and netstat to collect statistics, some deadlocks occurred. > This is quite a heavy patch trying to fix a bug... I suspect the root cause has nothing to do with stat collection since on 64bit arches there is no additional synchronization. (u64_stats_update_begin(), u64_stats_update_end() are nops) > +static inline void nv_get_stats(int cpu, struct fe_priv *np, > + struct rtnl_link_stats64 *storage) > +{ > + struct nv_txrx_stats *src = per_cpu_ptr(np->txrx_stats, cpu); > + unsigned int syncp_start; > + > + do { > + syncp_start = u64_stats_fetch_begin_irq(&np->swstats_rx_syncp); > + storage->rx_packets += src->stat_rx_packets; > + storage->rx_bytes += src->stat_rx_bytes; > + storage->rx_dropped += src->stat_rx_dropped; > + storage->rx_missed_errors += src->stat_rx_missed_errors; > + } while (u64_stats_fetch_retry_irq(&np->swstats_rx_syncp, syncp_start)); > + > + do { > + syncp_start = u64_stats_fetch_begin_irq(&np->swstats_tx_syncp); > + storage->tx_packets += src->stat_tx_packets; > + storage->tx_bytes += src->stat_tx_bytes; > + storage->tx_dropped += src->stat_tx_dropped; > + } while (u64_stats_fetch_retry_irq(&np->swstats_tx_syncp, syncp_start)); > +} > + > This is buggy : If the loops are ever restarted, the storage->fields will have been modified multiple times.