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 01EA8C33CAF for ; Thu, 16 Jan 2020 18:18:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id D00D3214AF for ; Thu, 16 Jan 2020 18:18:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579198721; bh=ZzZ/8amNPrAfUFfLxoXOQhRJPLpkIz5ndnCixuFh4m8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:List-ID:From; b=eLXsC+Qd8AFpIUiXK+CKRp3YuO6rWP+hEXQCbbGafcoRlQt3OaaXpbTpOseVHQLNW cBZX8nWAWgKuyfnysoKAmkHyC9i/QbcirqIF1cd4fSI8/IoCSwVQpPoNlBTO4/6yJx YduXJ366e1uT+QYCwFh1gup1zwINlrdoTIwwQ1zo= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2392638AbgAPR2n (ORCPT ); Thu, 16 Jan 2020 12:28:43 -0500 Received: from mail.kernel.org ([198.145.29.99]:39722 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2392594AbgAPR2e (ORCPT ); Thu, 16 Jan 2020 12:28:34 -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 12691246E6; Thu, 16 Jan 2020 17:28:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1579195713; bh=ZzZ/8amNPrAfUFfLxoXOQhRJPLpkIz5ndnCixuFh4m8=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=qdP0uJuF4FPmfWkrnE5w+N6XpyoFuEf4XPs9gpXctBttNWhJZca+mSzbHl/+TR3gx OaJKJFTeTQ+A62ylWCefot3RuOP4GeFlhU98nHfld42UXGaVqrY9zd/HqYREMBdoKC s7KCMB28HPYfOLS6c2Oxi6vamnwy2jlBMdsUC+R4= 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 4.14 258/371] tipc: reduce risk of wakeup queue starvation Date: Thu, 16 Jan 2020 12:22:10 -0500 Message-Id: <20200116172403.18149-201-sashal@kernel.org> X-Mailer: git-send-email 2.20.1 In-Reply-To: <20200116172403.18149-1-sashal@kernel.org> References: <20200116172403.18149-1-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 da749916faac..82e4e0e152d1 100644 --- a/net/tipc/link.c +++ b/net/tipc/link.c @@ -811,18 +811,31 @@ static int link_schedule_user(struct tipc_link *l, struct tipc_msg *hdr) */ 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