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 9A467C43219 for ; Mon, 6 Dec 2021 15:25:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1378101AbhLFP26 (ORCPT ); Mon, 6 Dec 2021 10:28:58 -0500 Received: from ams.source.kernel.org ([145.40.68.75]:58762 "EHLO ams.source.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1348018AbhLFPY5 (ORCPT ); Mon, 6 Dec 2021 10:24:57 -0500 Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 524C7B81125; Mon, 6 Dec 2021 15:21:27 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 97D9FC341C1; Mon, 6 Dec 2021 15:21:25 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1638804086; bh=tGCVU7G1+r3weFIpLm2SRUJIDptC8F7kGk49YmP4oDs=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=WAPzSQ8AaAEz1Bl2YhiJ1Vq5dDUg4bDcSI1gSt17je+jlOR8rygz3Rg5yN+nHktG/ Nu0nxlnhifKCs337K4zGHlCjQ69jtcsBGDYvZrN3PVykjN9ssLB01vEqq3piB3IlQn sMhyyUvsYRkqHnZKaUcmzDZQGG8ih1I56E7k5Bkw= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Wen Gu , Tony Lu , "David S. Miller" , Sasha Levin Subject: [PATCH 5.15 021/207] net/smc: Transfer remaining wait queue entries during fallback Date: Mon, 6 Dec 2021 15:54:35 +0100 Message-Id: <20211206145610.937621302@linuxfoundation.org> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20211206145610.172203682@linuxfoundation.org> References: <20211206145610.172203682@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Wen Gu [ Upstream commit 2153bd1e3d3dbf6a3403572084ef6ed31c53c5f0 ] The SMC fallback is incomplete currently. There may be some wait queue entries remaining in smc socket->wq, which should be removed to clcsocket->wq during the fallback. For example, in nginx/wrk benchmark, this issue causes an all-zeros test result: server: nginx -g 'daemon off;' client: smc_run wrk -c 1 -t 1 -d 5 http://11.200.15.93/index.html Running 5s test @ http://11.200.15.93/index.html 1 threads and 1 connections Thread Stats Avg Stdev Max ± Stdev Latency 0.00us 0.00us 0.00us -nan% Req/Sec 0.00 0.00 0.00 -nan% 0 requests in 5.00s, 0.00B read Requests/sec: 0.00 Transfer/sec: 0.00B The reason for this all-zeros result is that when wrk used SMC to replace TCP, it added an eppoll_entry into smc socket->wq and expected to be notified if epoll events like EPOLL_IN/ EPOLL_OUT occurred on the smc socket. However, once a fallback occurred, wrk switches to use clcsocket. Now it is clcsocket->wq instead of smc socket->wq which will be woken up. The eppoll_entry remaining in smc socket->wq does not work anymore and wrk stops the test. This patch fixes this issue by removing remaining wait queue entries from smc socket->wq to clcsocket->wq during the fallback. Link: https://www.spinics.net/lists/netdev/msg779769.html Signed-off-by: Wen Gu Reviewed-by: Tony Lu Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/smc/af_smc.c | 14 ++++++++++++++ 1 file changed, 14 insertions(+) diff --git a/net/smc/af_smc.c b/net/smc/af_smc.c index 3d8219e3b0264..c0456cb7623cb 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -548,6 +548,10 @@ static void smc_stat_fallback(struct smc_sock *smc) static void smc_switch_to_fallback(struct smc_sock *smc, int reason_code) { + wait_queue_head_t *smc_wait = sk_sleep(&smc->sk); + wait_queue_head_t *clc_wait = sk_sleep(smc->clcsock->sk); + unsigned long flags; + smc->use_fallback = true; smc->fallback_rsn = reason_code; smc_stat_fallback(smc); @@ -556,6 +560,16 @@ static void smc_switch_to_fallback(struct smc_sock *smc, int reason_code) smc->clcsock->file->private_data = smc->clcsock; smc->clcsock->wq.fasync_list = smc->sk.sk_socket->wq.fasync_list; + + /* There may be some entries remaining in + * smc socket->wq, which should be removed + * to clcsocket->wq during the fallback. + */ + spin_lock_irqsave(&smc_wait->lock, flags); + spin_lock(&clc_wait->lock); + list_splice_init(&smc_wait->head, &clc_wait->head); + spin_unlock(&clc_wait->lock); + spin_unlock_irqrestore(&smc_wait->lock, flags); } } -- 2.33.0