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 0C3E6C433EF for ; Fri, 26 Nov 2021 02:40:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1343681AbhKZCny (ORCPT ); Thu, 25 Nov 2021 21:43:54 -0500 Received: from mail.kernel.org ([198.145.29.99]:49854 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1358537AbhKZClp (ORCPT ); Thu, 25 Nov 2021 21:41:45 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 74AC861262; Fri, 26 Nov 2021 02:34:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1637894096; bh=GkcSQMSSz3XxRMsTMPfS8NF2WvHvNbeB8VLVVh5mg40=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=TdhNKpP9YgPQbPjSdlkUWtulWs0xFMxlndsLQEhMhLe5FyRp3lglURdgft94l07ON J0JKXvLdHkjpqqFm+unNl+XTRvJAVoD9sIFqkLDLJxJKVjUM6/YYeLwmfLDlML/k5V a3j3+q2QYRXgpcwBJuvlyQcKm7WuFGg1DCeI0v48p6Z8q+Ky7K0lRiPVv68aPUBVeU lAb2dyXlTFV4gPo38zE/CgNN8G+CDzzg96K6s7rQ2H5w7COjvmjVToXqHbUIytXduy Jmrs9nJjIVKnPBAKcoxwsR4VpJXUYQP4H9hWt7dLGnTzc5z4X2R12qFQ6jKx17W2ZT Ildel5TCzenPw== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Wen Gu , Tony Lu , "David S . Miller" , Sasha Levin , kgraul@linux.ibm.com, kuba@kernel.org, linux-s390@vger.kernel.org, netdev@vger.kernel.org Subject: [PATCH AUTOSEL 5.4 05/19] net/smc: Transfer remaining wait queue entries during fallback Date: Thu, 25 Nov 2021 21:34:34 -0500 Message-Id: <20211126023448.442529-5-sashal@kernel.org> X-Mailer: git-send-email 2.33.0 In-Reply-To: <20211126023448.442529-1-sashal@kernel.org> References: <20211126023448.442529-1-sashal@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@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 6b0f09c5b195f..1fad05d6dd9ad 100644 --- a/net/smc/af_smc.c +++ b/net/smc/af_smc.c @@ -467,12 +467,26 @@ static void smc_link_save_peer_info(struct smc_link *link, static void smc_switch_to_fallback(struct smc_sock *smc) { + 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; if (smc->sk.sk_socket && smc->sk.sk_socket->file) { smc->clcsock->file = smc->sk.sk_socket->file; 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