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=-3.7 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED 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 CF16CC3A5A1 for ; Wed, 28 Aug 2019 04:38:10 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id ABCEF2173E for ; Wed, 28 Aug 2019 04:38:10 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726101AbfH1EiJ (ORCPT ); Wed, 28 Aug 2019 00:38:09 -0400 Received: from shards.monkeyblade.net ([23.128.96.9]:54752 "EHLO shards.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725827AbfH1EiJ (ORCPT ); Wed, 28 Aug 2019 00:38:09 -0400 Received: from localhost (unknown [IPv6:2601:601:9f80:35cd::d71]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) (Authenticated sender: davem-davemloft) by shards.monkeyblade.net (Postfix) with ESMTPSA id 67F86153BF45E; Tue, 27 Aug 2019 21:38:08 -0700 (PDT) Date: Tue, 27 Aug 2019 21:38:05 -0700 (PDT) Message-Id: <20190827.213805.294784850249692598.davem@davemloft.net> To: edumazet@google.com Cc: netdev@vger.kernel.org, soheil@google.com, ncardwell@google.com, eric.dumazet@gmail.com, jbaron@akamai.com, rutsky@google.com Subject: Re: [PATCH net] tcp: remove empty skb from write queue in error cases From: David Miller In-Reply-To: <20190826161915.81676-1-edumazet@google.com> References: <20190826161915.81676-1-edumazet@google.com> X-Mailer: Mew version 6.8 on Emacs 26.1 Mime-Version: 1.0 Content-Type: Text/Plain; charset=us-ascii Content-Transfer-Encoding: 7bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.5.12 (shards.monkeyblade.net [149.20.54.216]); Tue, 27 Aug 2019 21:38:08 -0700 (PDT) Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org From: Eric Dumazet Date: Mon, 26 Aug 2019 09:19:15 -0700 > Vladimir Rutsky reported stuck TCP sessions after memory pressure > events. Edge Trigger epoll() user would never receive an EPOLLOUT > notification allowing them to retry a sendmsg(). > > Jason tested the case of sk_stream_alloc_skb() returning NULL, > but there are other paths that could lead both sendmsg() and sendpage() > to return -1 (EAGAIN), with an empty skb queued on the write queue. > > This patch makes sure we remove this empty skb so that > Jason code can detect that the queue is empty, and > call sk->sk_write_space(sk) accordingly. > > Fixes: ce5ec440994b ("tcp: ensure epoll edge trigger wakeup when write queue is empty") > Signed-off-by: Eric Dumazet > Cc: Jason Baron > Reported-by: Vladimir Rutsky Applied and queued up for -stable.