Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755695AbdGCNoR (ORCPT ); Mon, 3 Jul 2017 09:44:17 -0400 Received: from mail.linuxfoundation.org ([140.211.169.12]:36560 "EHLO mail.linuxfoundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932777AbdGCNoO (ORCPT ); Mon, 3 Jul 2017 09:44:14 -0400 From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, Vineeth Remanan Pillai , Juergen Gross , "David S. Miller" , Sasha Levin Subject: [PATCH 4.9 085/172] xen-netfront: Fix Rx stall during network stress and OOM Date: Mon, 3 Jul 2017 15:34:25 +0200 Message-Id: <20170703133418.262721186@linuxfoundation.org> X-Mailer: git-send-email 2.13.2 In-Reply-To: <20170703133414.260777365@linuxfoundation.org> References: <20170703133414.260777365@linuxfoundation.org> User-Agent: quilt/0.65 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1645 Lines: 44 4.9-stable review patch. If anyone has any objections, please let me know. ------------------ From: Vineeth Remanan Pillai [ Upstream commit 90c311b0eeead647b708a723dbdde1eda3dcad05 ] During an OOM scenario, request slots could not be created as skb allocation fails. So the netback cannot pass in packets and netfront wrongly assumes that there is no more work to be done and it disables polling. This causes Rx to stall. The issue is with the retry logic which schedules the timer if the created slots are less than NET_RX_SLOTS_MIN. The count of new request slots to be pushed are calculated as a difference between new req_prod and rsp_cons which could be more than the actual slots, if there are unconsumed responses. The fix is to calculate the count of newly created slots as the difference between new req_prod and old req_prod. Signed-off-by: Vineeth Remanan Pillai Reviewed-by: Juergen Gross Signed-off-by: David S. Miller Signed-off-by: Sasha Levin Signed-off-by: Greg Kroah-Hartman --- drivers/net/xen-netfront.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -321,7 +321,7 @@ static void xennet_alloc_rx_buffers(stru queue->rx.req_prod_pvt = req_prod; /* Not enough requests? Try again later. */ - if (req_prod - queue->rx.rsp_cons < NET_RX_SLOTS_MIN) { + if (req_prod - queue->rx.sring->req_prod < NET_RX_SLOTS_MIN) { mod_timer(&queue->rx_refill_timer, jiffies + (HZ/10)); return; }