From patchwork Tue Jan 5 18:58:54 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Vladimir Oltean X-Patchwork-Id: 12000191 X-Patchwork-Delegate: kuba@kernel.org 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=-15.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=ham 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 48E66C4160E for ; Tue, 5 Jan 2021 19:02:46 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 1C86122D6D for ; Tue, 5 Jan 2021 19:02:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730845AbhAETC2 (ORCPT ); Tue, 5 Jan 2021 14:02:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43272 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725838AbhAETCH (ORCPT ); Tue, 5 Jan 2021 14:02:07 -0500 Received: from mail-ej1-x636.google.com (mail-ej1-x636.google.com [IPv6:2a00:1450:4864:20::636]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 25E13C0617A2; Tue, 5 Jan 2021 11:00:53 -0800 (PST) Received: by mail-ej1-x636.google.com with SMTP id w1so1758613ejf.11; Tue, 05 Jan 2021 11:00:53 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=VqKUbghIDfYrfb3O7qIi6ZxV/2bVKA7+VXpaNALoN60=; b=o72EV0y5XH6HchkYJqkf18+T0vm0Uz19QPiFec6UrE0bJV5bAouj5tUFThd+IbUeaH yUe448KhNG1blJQxDZTQOSx3bw/rjUuPJafSLUnhGcVcmX+vwhSeVoHv6FFJBmfUSV+u a+CFVILyASpZpXFmOVMNnfqc28/9V6Dagm/1/RVHEVBz9ZLAMbGJ2DgFzJCl+FaHemvK 1GjY//UjxbnawtELZ84EsOXDBNfazICZGH71XgnOA+CXCFm1CTMHQfQ9UV70yrAuXfPB oS/PFIl8l1oqOkgmzlk+HI19tTlFGLDsv257e3gWMIM1kgKEOxMeY7CZjnCo1NcYYmKo gsYw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=VqKUbghIDfYrfb3O7qIi6ZxV/2bVKA7+VXpaNALoN60=; b=M1hutG4tPrb4hRVKgwJ0Eg1RUHkNyiR0cC4WrgZI4iiC7Swpc7K1yq8N5SifqP1ZLu hqiO1N+HWterCDoTORwQ3FCeHH2y5RvBz9KZxbhbD8bsV0urLW5RtKpGDszsYFsd7z5K kfw6zsx5MxJRqCIPzPnVZCI4GAyXxl7itZ79+snsCX2aiw2Du8ryKcVn7BDt7uEsQESg 9V2pIvLcrkMUyRed6IIc6pCQWeyv0TAC0rptoraJZJjYiyw2WQuoGbekEcH48AQQtGWa oD1vM9vuhziETvh7C6AmYmH7jpTgX/1yuVp+i5fbv8az0V5zMTjH/4YfCpvgOlHn2yuB roJg== X-Gm-Message-State: AOAM531RutI4t0UBg4w1Xo31Gt+X70Mhk2pFxwDCIyMnGftIZ5/6JPeB SCtV2mABQMJQtisH1TP5JQQ= X-Google-Smtp-Source: ABdhPJz1wURDbCR0bNBYRS2W9HuLCgl2tOQ8FkzBLbjCThN+VIxGm1iq/S2lOXku8roTHNgJI/WFnQ== X-Received: by 2002:a17:906:f0cc:: with SMTP id dk12mr488324ejb.480.1609873251916; Tue, 05 Jan 2021 11:00:51 -0800 (PST) Received: from localhost.localdomain (5-12-227-87.residential.rdsnet.ro. [5.12.227.87]) by smtp.gmail.com with ESMTPSA id z13sm205084edq.48.2021.01.05.11.00.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 05 Jan 2021 11:00:51 -0800 (PST) From: Vladimir Oltean To: "David S . Miller" , Jakub Kicinski Cc: netdev@vger.kernel.org, Andrew Lunn , Florian Fainelli , Paul Gortmaker , Pablo Neira Ayuso , Jiri Benc , Cong Wang , Jamal Hadi Salim , Stephen Hemminger , Eric Dumazet , George McCollister , Oleksij Rempel , Jay Vosburgh , Veaceslav Falico , Andy Gospodarek , Arnd Bergmann , Alexei Starovoitov , Andrii Nakryiko , Daniel Borkmann , Taehee Yoo , Jiri Pirko , =?utf-8?b?QmrDtnJuIFTDtnBlbA==?= , Paolo Abeni , Christian Brauner , Florian Westphal , linux-s390@vger.kernel.org, intel-wired-lan@lists.osuosl.org, linux-parisc@vger.kernel.org, linux-scsi@vger.kernel.org, linux-usb@vger.kernel.org, dev@openvswitch.org Subject: [RFC PATCH v2 net-next 04/12] net: sysfs: don't hold dev_base_lock while retrieving device statistics Date: Tue, 5 Jan 2021 20:58:54 +0200 Message-Id: <20210105185902.3922928-5-olteanv@gmail.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20210105185902.3922928-1-olteanv@gmail.com> References: <20210105185902.3922928-1-olteanv@gmail.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org X-Patchwork-Delegate: kuba@kernel.org X-Patchwork-State: RFC From: Vladimir Oltean In the effort of making .ndo_get_stats64 be able to sleep, we need to ensure the callers of dev_get_stats do not use atomic context. I need to preface this by saying that I have no idea why netstat_show takes the dev_base_lock rwlock. Two things can be observed: (a) it does not appear to be due to dev_isalive requiring it for some reason, because broadcast_show() also calls dev_isalive() and has had no problem existing since the beginning of git. (b) the dev_get_stats function definitely does not need dev_base_lock protection either. In fact, holding the dev_base_lock is the entire problem here, because we want to make dev_get_stats sleepable, and holding a rwlock gives us atomic context. So since no protection seems to be necessary, just run unlocked while retrieving the /sys/class/net/eth0/statistics/* values. Cc: Christian Brauner Cc: Eric Dumazet Signed-off-by: Vladimir Oltean --- net/core/net-sysfs.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c index 999b70c59761..0782a476b424 100644 --- a/net/core/net-sysfs.c +++ b/net/core/net-sysfs.c @@ -585,14 +585,13 @@ static ssize_t netstat_show(const struct device *d, WARN_ON(offset > sizeof(struct rtnl_link_stats64) || offset % sizeof(u64) != 0); - read_lock(&dev_base_lock); if (dev_isalive(dev)) { struct rtnl_link_stats64 temp; const struct rtnl_link_stats64 *stats = dev_get_stats(dev, &temp); ret = sprintf(buf, fmt_u64, *(u64 *)(((u8 *)stats) + offset)); } - read_unlock(&dev_base_lock); + return ret; }