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=-11.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED,USER_IN_DEF_DKIM_WL 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 32817C433DF for ; Fri, 16 Oct 2020 07:35:57 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id C66F820829 for ; Fri, 16 Oct 2020 07:35:56 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="ufPK33+a" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2404702AbgJPHfz (ORCPT ); Fri, 16 Oct 2020 03:35:55 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46512 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2404697AbgJPHfz (ORCPT ); Fri, 16 Oct 2020 03:35:55 -0400 Received: from mail-io1-xd42.google.com (mail-io1-xd42.google.com [IPv6:2607:f8b0:4864:20::d42]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 2F66CC061755 for ; Fri, 16 Oct 2020 00:35:55 -0700 (PDT) Received: by mail-io1-xd42.google.com with SMTP id k21so2577707ioa.9 for ; Fri, 16 Oct 2020 00:35:55 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=u7qwW5lwtSNOyHDsTGnqiNPRJU2aYDZFjJeR0++aK1s=; b=ufPK33+a6DMS19HuUhiP+YaWzOvOCgwd6PHGvMRqSl1NCysvR2wkcUcRN2vF5y6pso /Sv/1VfyryYZMviTMiaQzuLoyDd3Tsn0KzJcgNtDVPF/vJ4nTAdQx2y9iNjap2bc64zZ 04/M4awGLloQ4UGg17kiOXgNyy4QdCbvODnyrzfmw9yp6ZUhEOQXTyXjPMIslF2M12sd M4TIodJNsZXF49EFJvLTj2QkFbm/tdl2Cma4rug03wnBJXVy30ui/KDoi6Sp0y9gBhzm oH6UaKPDjHr5sv+b+IunkAKrYGF2YB/9K4Z/ajtjI03rYtMLt2ckoPsQ4OPubZ/knFiM NV8Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=u7qwW5lwtSNOyHDsTGnqiNPRJU2aYDZFjJeR0++aK1s=; b=nFrMao5+ckz0syOBI6ztO64RuWVgCZk29Li1T26pqYmnqAjWpaN3WerSTn/2NKx1CJ SOACvhbc3bm3jrW87/3WfxyA7cZcmzQigsNsFDjz8YMzXvH4py2TCSNC8eHJJWcXjWmE glTC0eJyDBSA0G6nCByP7zUB7zAGhxvptAcZTQz22Jx0tf0bwPtaAXC858AwY1lmROIP +u8eD0r5LFY8T8xXEXTHd60tiHoG2TUD6LIQMjASvoWVQA8ncHjcNEtTHvz8BPUiBd6P O3BKWAqeNVUD0Gq2YpBCzqaSWcMIzu0VsaEqguHQQsWA/hVY3XjNtteNyVk8t5kJjpHG f0kg== X-Gm-Message-State: AOAM530iJpre/4PdWJtdBcGTDPi79pT3kM7iitCFKgroryMZytwqA2b4 dh7OJkFdc8drTei2zLPO+Cf/ym6WAwUYlO7aze5QkA== X-Google-Smtp-Source: ABdhPJwcfgXIR+cI+ss38HA116PtIf+68m2rajno9lnuKm4tv4c3BiaOpdylggHq6V68olVkcAGUDwL7+qDs+lB2Mlk= X-Received: by 2002:a5e:c112:: with SMTP id v18mr1498419iol.195.1602833754271; Fri, 16 Oct 2020 00:35:54 -0700 (PDT) MIME-Version: 1.0 References: <87eelz4abk.fsf@marvin.dmesg.gr> <87blh33zr7.fsf@marvin.dmesg.gr> In-Reply-To: From: Eric Dumazet Date: Fri, 16 Oct 2020 09:35:42 +0200 Message-ID: Subject: Re: TCP sender stuck in persist despite peer advertising non-zero window To: Neal Cardwell Cc: Apollon Oikonomopoulos , Yuchung Cheng , Netdev , Soheil Hassas Yeganeh Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Fri, Oct 16, 2020 at 12:37 AM Neal Cardwell wrote: > > On Thu, Oct 15, 2020 at 6:12 PM Apollon Oikonomopoulos wrote: > > > > Yuchung Cheng writes: > > > > > On Thu, Oct 15, 2020 at 1:22 PM Neal Cardwell wrote: > > >> > > >> On Thu, Oct 15, 2020 at 2:31 PM Apollon Oikonomopoulos wrote: > > >> > > > >> > Hi, > > >> > > > >> > I'm trying to debug a (possible) TCP issue we have been encountering > > >> > sporadically during the past couple of years. Currently we're running > > >> > 4.9.144, but we've been observing this since at least 3.16. > > >> > > > >> > Tl;DR: I believe we are seeing a case where snd_wl1 fails to be properly > > >> > updated, leading to inability to recover from a TCP persist state and > > >> > would appreciate some help debugging this. > > >> > > >> Thanks for the detailed report and diagnosis. I think we may need a > > >> fix something like the following patch below. > > > > That was fast, thank you! > > > > >> > > >> Eric/Yuchung/Soheil, what do you think? > > > wow hard to believe how old this bug can be. The patch looks good but > > > can Apollon verify this patch fix the issue? > > > > Sure, I can give it a try and let the systems do their thing for a couple of > > days, which should be enough to see if it's fixed. > > Great, thanks! > > > Neal, would it be possible to re-send the patch as an attachment? The > > inlined version does not apply cleanly due to linewrapping and > > whitespace changes and, although I can re-type it, I would prefer to test > > the exact same thing that would be merged. > > Sure, I have attached the "git format-patch" format of the commit. It > does seem to apply cleanly to the v4.9.144 kernel you mentioned you > are using. > > Thanks for testing this! > > best, > neal Ouch, this is an interesting bug. Would netperf -t TCP_RR -- -r 2GB,2GB " be a possible test ? (I am afraid packetdrill won't be able to test this in a reasonable amount of time) Neal, can you include in your changelog the link to Apollon awesome email, I think it was a very nice investigation and Apollon deserves more credit than a mere "Reported-by:" tag ;) Maybe this one : Link: https://www.spinics.net/lists/netdev/msg692430.html Thanks !