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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4FDB0C61DA4 for ; Mon, 13 Mar 2023 20:18:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229748AbjCMUSc (ORCPT ); Mon, 13 Mar 2023 16:18:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:58606 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230162AbjCMUSV (ORCPT ); Mon, 13 Mar 2023 16:18:21 -0400 Received: from mail-qt1-x84a.google.com (mail-qt1-x84a.google.com [IPv6:2607:f8b0:4864:20::84a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 282046A4A for ; Mon, 13 Mar 2023 13:17:38 -0700 (PDT) Received: by mail-qt1-x84a.google.com with SMTP id br8-20020a05622a1e0800b003c0189c37e1so7448516qtb.18 for ; Mon, 13 Mar 2023 13:17:38 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; t=1678738657; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=qZNjZylXpZlqsXSx5fBI7eF05UVsFDZXf0HIJTTFwZ4=; b=RUEXji35P58EBsU0G4AHGH/GCWCHDgwJhoKyi+Ctqz9E94qdR+cGWSkAbkwIESkEoO 9kZpPIxKT7Xvp+I+pBbIRtBbN1P+/fkHp3aodaPrv0rd1r1TTBOB7Hx8+Mx9VJwFluMB 0AG+mXwML9BlbnxbwVDvdbBKLvzOxyt23+qhagEUcD+szuBoTyrGzrLVlv81Ufiz/qbq yhz1a55wuWI2OIqydIZNDq4srgbt1D2vdijvayYYyP/Z4Vpp7rjEZNQMg7/zFUnXqXaM 3Hvo8e4Ve0DZVkNWnlBd8IEiAg6NJ7wo6oXztZ71J5SsTAmiNuEcgiMd1nGyppB8X4Sw +0Eg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; t=1678738657; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=qZNjZylXpZlqsXSx5fBI7eF05UVsFDZXf0HIJTTFwZ4=; b=g7aCgzXP7Eeaf+oycGfg0m+WzlLZ2QWPheqY3o07vmtldFmnfKdqtCjeR+b0OP9FL1 MJgNmw6VEjP+cUMw9+OdxKsHcIiou5zpfwsxDEHWe6DP4xSZ2NlfPMkOA7ixQlFmtxVo nHif5q46BzlouBl84Ccmo6eJu2PlgnFxvxK7JWqs7LI7GtBsrPztM30Nfv6N+OMnuxds 4cuVwje7ZD9VfFBN2LrRTDliKM/voUVLd3BPJOg7hGVXX5xMQi9oMnz7/QK5K9TdupQu +9e37kuciFx7ME+VQxtAAri9I4v9XX/gDexlCdA1rIcNFYuj0XE4OY7kP66fMYnKkTRW UYgg== X-Gm-Message-State: AO0yUKW0igi4yxDOsTdwqxEFavVY11rPdj4e/sre9BrO7LCLxaRVApQm 12nNsDrmLTxiuT4vUt2sYn/Dv9dhyvzITA== X-Google-Smtp-Source: AK7set9kbS6F/sKA03QV+hMZs3Sdvj1T6gvuScY/dsMR/YudxLt0AA769JWYyaAI4mmxJ3tpZxzur6hTfSOcxw== X-Received: from edumazet1.c.googlers.com ([fda3:e722:ac3:cc00:2b:7d90:c0a8:395a]) (user=edumazet job=sendgmr) by 2002:ae9:f00d:0:b0:745:6afc:9bb2 with SMTP id l13-20020ae9f00d000000b007456afc9bb2mr1516718qkg.14.1678738657306; Mon, 13 Mar 2023 13:17:37 -0700 (PDT) Date: Mon, 13 Mar 2023 20:17:32 +0000 In-Reply-To: <20230313201732.887488-1-edumazet@google.com> Mime-Version: 1.0 References: <20230313201732.887488-1-edumazet@google.com> X-Mailer: git-send-email 2.40.0.rc1.284.g88254d51c5-goog Message-ID: <20230313201732.887488-3-edumazet@google.com> Subject: [PATCH net-next 2/2] ipv6: remove one read_lock()/read_unlock() pair in rt6_check_neigh() From: Eric Dumazet To: "David S . Miller" , Jakub Kicinski , Paolo Abeni Cc: David Ahern , netdev@vger.kernel.org, eric.dumazet@gmail.com, Eric Dumazet Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org rt6_check_neigh() uses read_lock() to protect n->nud_state reading. This seems overkill and causes false sharing. Signed-off-by: Eric Dumazet --- net/ipv6/route.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/net/ipv6/route.c b/net/ipv6/route.c index 25c00c6f5131c55055f30348ef4605f50440ddbb..e829bd880384077027dc79fcae1a62eb0073f7c8 100644 --- a/net/ipv6/route.c +++ b/net/ipv6/route.c @@ -687,16 +687,16 @@ static enum rt6_nud_state rt6_check_neigh(const struct fib6_nh *fib6_nh) neigh = __ipv6_neigh_lookup_noref(fib6_nh->fib_nh_dev, &fib6_nh->fib_nh_gw6); if (neigh) { - read_lock(&neigh->lock); - if (neigh->nud_state & NUD_VALID) + u8 nud_state = READ_ONCE(neigh->nud_state); + + if (nud_state & NUD_VALID) ret = RT6_NUD_SUCCEED; #ifdef CONFIG_IPV6_ROUTER_PREF - else if (!(neigh->nud_state & NUD_FAILED)) + else if (!(nud_state & NUD_FAILED)) ret = RT6_NUD_SUCCEED; else ret = RT6_NUD_FAIL_PROBE; #endif - read_unlock(&neigh->lock); } else { ret = IS_ENABLED(CONFIG_IPV6_ROUTER_PREF) ? RT6_NUD_SUCCEED : RT6_NUD_FAIL_DO_RR; -- 2.40.0.rc1.284.g88254d51c5-goog