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 2E09AC0015E for ; Fri, 21 Jul 2023 15:55:46 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231352AbjGUPzp (ORCPT ); Fri, 21 Jul 2023 11:55:45 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:56054 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231743AbjGUPzk (ORCPT ); Fri, 21 Jul 2023 11:55:40 -0400 Received: from mail-pf1-x42a.google.com (mail-pf1-x42a.google.com [IPv6:2607:f8b0:4864:20::42a]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C2B9C35A0; Fri, 21 Jul 2023 08:55:23 -0700 (PDT) Received: by mail-pf1-x42a.google.com with SMTP id d2e1a72fcca58-6862842a028so1405319b3a.0; Fri, 21 Jul 2023 08:55:23 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20221208; t=1689954923; x=1690559723; h=to:references:message-id:content-transfer-encoding:cc:date :in-reply-to:from:subject:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=F9Nkz09J0OWI8g55rIWxy1NKC5S7asE7sS8B85Det4w=; b=Tuv9oN/LT9x0NGtgdwqfgzNpbSMdVfxcVtV2YUFxa5Lnf7p0nkDaGoMM0CHpt/4rlb c5rQ1zZyK5Tar0Q2eTbyuKQFZAcXfMwZEnIFXeFQ9OSEXLvYNzcPAcrCp5+NohdmF9PX 5UJdxpqzSEpbqsBN6Vt1opak5tnVfFqfms0JbBvu5xDIGxR0fBAcR5N0GMmHwHFYMkXw zxJwds8Rdvcv5MfF7W4sGuArBm4OUYiejAdhd7pKJ1IGZ+n0A1ZUmiCJ/q3dVM4/y1kz Lmg93CxUIpdD2+gMb1SQZGmJQLy3vmAaCjITR4AeKMmJ3bC6BpDBvdq9Sx0Wsc5KupGd gLyg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20221208; t=1689954923; x=1690559723; h=to:references:message-id:content-transfer-encoding:cc:date :in-reply-to:from:subject:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=F9Nkz09J0OWI8g55rIWxy1NKC5S7asE7sS8B85Det4w=; b=G/7222/oYsEzMKPO5PX/6CulUYZql34oGBsrgqvLyjQgTlLJGY7aK2vPIlAJyWIA7J oSh3UylvpNb+bq4QINcKg2Oew6BFceeqRsSeISa05QrRJnxy7fOGOjoFhM77qUrf59K9 BEcxVo0k5A5D/tGcO/89ZllSLmJLWkcDIzv2yVDwBRZ+y2SR2Pm2amVDYj6pqtTIFT7e 1HMQYZI9JFL6UZGOU0LJLwSQTdREo4LzobltBpNvantZm+PkV7QUB4wFu3s4Gpqa30It 7uBELQeKFPhTXmVb2duxXo00aIbTD643QZPSPevgk3tcEb00Y5S6G4ZRmDD4htdNmy4w O7Ew== X-Gm-Message-State: ABy/qLaSPGPkYccr3uFVJ8d+EwW9Rm+PdPcfYMXs7KMbfqjf8HzD7enB EuqLInL9QJaWjmfONmdFELc= X-Google-Smtp-Source: APBJJlFPtxydAoiHWHkJISTHNoF9Jsw9EbnmsgBFnnI9ZibNZVSsa6Iv55dcnAUzUA0ld3ftX4P6pw== X-Received: by 2002:a05:6a00:b45:b0:676:20f8:be41 with SMTP id p5-20020a056a000b4500b0067620f8be41mr484404pfo.16.1689954923244; Fri, 21 Jul 2023 08:55:23 -0700 (PDT) Received: from smtpclient.apple ([2402:d0c0:2:a2a::1]) by smtp.gmail.com with ESMTPSA id y8-20020a62b508000000b00663b712bfbdsm3145756pfe.57.2023.07.21.08.55.17 (version=TLS1_2 cipher=ECDHE-ECDSA-AES128-GCM-SHA256 bits=128/128); Fri, 21 Jul 2023 08:55:22 -0700 (PDT) Content-Type: text/plain; charset=utf-8 Mime-Version: 1.0 (Mac OS X Mail 16.0 \(3731.400.51.1.1\)) Subject: Re: Question about the barrier() in hlist_nulls_for_each_entry_rcu() From: Alan Huang In-Reply-To: Date: Fri, 21 Jul 2023 23:55:07 +0800 Cc: "linux-kernel@vger.kernel.org" , "netdev@vger.kernel.org" , "rcu@vger.kernel.org" , "Paul E. McKenney" , Eric Dumazet , "roman.gushchin@linux.dev" Content-Transfer-Encoding: quoted-printable Message-Id: References: <04C1E631-725C-47AD-9914-25D5CE04DFF4@gmail.com> To: David Laight X-Mailer: Apple Mail (2.3731.400.51.1.1) Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org > 2023=E5=B9=B47=E6=9C=8821=E6=97=A5 19:51=EF=BC=8CDavid Laight = =E5=86=99=E9=81=93=EF=BC=9A >=20 > From: Alan Huang >> Sent: 20 July 2023 19:54 >>=20 >> I noticed a commit c87a124a5d5e(=E2=80=9Cnet: force a reload of first = item in hlist_nulls_for_each_entry_rcu=E2=80=9D) >> and a related discussion [1]. >=20 > Hmmm... that was all about the retry loop in ipv4/udp.c >=20 > AFAICT that retry got deleted by ca065d0c. >=20 > That also changes the list from hlist_nulls_xxx to hlist_xxx. > (I'm not sure of the difference) >=20 > This might be why we're seeing unexpected 'port unreachable' messages? >=20 > Quite why that has just started happening is another issue. > Most of the UDP sockets we create aren't 'connected' so I don't > believe they get moved between hash chains - just deleted. > The deletion should leave the hash chain intact. Thanks for the information! :) >=20 > David >=20 > - > Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, = MK1 1PT, UK > Registration No: 1397386 (Wales)