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=-10.1 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY, SPF_HELO_NONE,SPF_PASS,USER_AGENT_GIT autolearn=unavailable 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 465CAC33CB3 for ; Thu, 16 Jan 2020 18:46:44 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 20AE120661 for ; Thu, 16 Jan 2020 18:46:44 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579200404; bh=NgKJG50v26t3Vf5avitvxO+GSugw3D1BEER2ab+VStk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=eVOOPLSvF4RngBhRYkryBZari5iu8XughQIHH5agNfIfDiHGWF7F/2TbeY2FFgSTM 4FBfgsnrrXiHQTARZseNYnkIParKltXn/aIokyVJU/cYENvBymzz+GoEpn9BIRv9b5 WhX/53ImRBTviOG2D/NUX88A/AYfVJT7vFwMT5Lw= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2390114AbgAPSqm (ORCPT ); Thu, 16 Jan 2020 13:46:42 -0500 Received: from mail.kernel.org ([198.145.29.99]:47792 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2389868AbgAPRKN (ORCPT ); Thu, 16 Jan 2020 12:10:13 -0500 Received: from sasha-vm.mshome.net (c-73-47-72-35.hsd1.nh.comcast.net [73.47.72.35]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 61E5F205F4; Thu, 16 Jan 2020 17:10:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579194612; bh=NgKJG50v26t3Vf5avitvxO+GSugw3D1BEER2ab+VStk=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=eOHT1+9NgaePYBr42Kl0Cpm66o1YA5MM+tUBByajiOaxFxM9meCR4wZRqAmpieFss seTYkEa+sG6CUy2gi9Kk+bIHWBh8Oo2byKiNMZdrOiSs0g/r9+ehfzWXBcjhCEUGlb EUoxvva2Md/jSFzdxAEuu5UXg9/JU81zQwwLVaL8= From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Jon Maloy , Tung Nguyen , Ying Xue , "David S . Miller" , Sasha Levin , netdev@vger.kernel.org, tipc-discussion@lists.sourceforge.net Subject: [PATCH AUTOSEL 4.19 477/671] tipc: reduce risk of wakeup queue starvation Date: Thu, 16 Jan 2020 12:01:55 -0500 Message-Id: <20200116170509.12787-214-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200116170509.12787-1-sashal@kernel.org> References: <20200116170509.12787-1-sashal@kernel.org> MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore Content-Transfer-Encoding: 8bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Jon Maloy [ Upstream commit 7c5b42055964f587e55bd87ef334c3a27e95d144 ] In commit 365ad353c256 ("tipc: reduce risk of user starvation during link congestion") we allowed senders to add exactly one list of extra buffers to the link backlog queues during link congestion (aka "oversubscription"). However, the criteria for when to stop adding wakeup messages to the input queue when the overload abates is inaccurate, and may cause starvation problems during very high load. Currently, we stop adding wakeup messages after 10 total failed attempts where we find that there is no space left in the backlog queue for a certain importance level. The counter for this is accumulated across all levels, which may lead the algorithm to leave the loop prematurely, although there may still be plenty of space available at some levels. The result is sometimes that messages near the wakeup queue tail are not added to the input queue as they should be. We now introduce a more exact algorithm, where we keep adding wakeup messages to a level as long as the backlog queue has free slots for the corresponding level, and stop at the moment there are no more such slots or when there are no more wakeup messages to dequeue. Fixes: 365ad35 ("tipc: reduce risk of user starvation during link congestion") Reported-by: Tung Nguyen Acked-by: Ying Xue Signed-off-by: Jon Maloy Signed-off-by: David S. Miller Signed-off-by: Sasha Levin --- net/tipc/link.c | 29 +++++++++++++++++++++-------- 1 file changed, 21 insertions(+), 8 deletions(-) diff --git a/net/tipc/link.c b/net/tipc/link.c index 0fbf8ea18ce0..cc9a0485536b 100644 --- a/net/tipc/link.c +++ b/net/tipc/link.c @@ -830,18 +830,31 @@ static int link_schedule_user(struct tipc_link *l, struct tipc_msg *hdr) */ static void link_prepare_wakeup(struct tipc_link *l) { + struct sk_buff_head *wakeupq = &l->wakeupq; + struct sk_buff_head *inputq = l->inputq; struct sk_buff *skb, *tmp; - int imp, i = 0; + struct sk_buff_head tmpq; + int avail[5] = {0,}; + int imp = 0; + + __skb_queue_head_init(&tmpq); - skb_queue_walk_safe(&l->wakeupq, skb, tmp) { + for (; imp <= TIPC_SYSTEM_IMPORTANCE; imp++) + avail[imp] = l->backlog[imp].limit - l->backlog[imp].len; + + skb_queue_walk_safe(wakeupq, skb, tmp) { imp = TIPC_SKB_CB(skb)->chain_imp; - if (l->backlog[imp].len < l->backlog[imp].limit) { - skb_unlink(skb, &l->wakeupq); - skb_queue_tail(l->inputq, skb); - } else if (i++ > 10) { - break; - } + if (avail[imp] <= 0) + continue; + avail[imp]--; + __skb_unlink(skb, wakeupq); + __skb_queue_tail(&tmpq, skb); } + + spin_lock_bh(&inputq->lock); + skb_queue_splice_tail(&tmpq, inputq); + spin_unlock_bh(&inputq->lock); + } void tipc_link_reset(struct tipc_link *l) -- 2.20.1