From patchwork Tue Oct 15 09:34:57 2013 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: jianhai luan X-Patchwork-Id: 283553 X-Patchwork-Delegate: davem@davemloft.net Return-Path: X-Original-To: patchwork-incoming@ozlabs.org Delivered-To: patchwork-incoming@ozlabs.org Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by ozlabs.org (Postfix) with ESMTP id 668FD2C012D for ; Tue, 15 Oct 2013 20:35:21 +1100 (EST) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754403Ab3JOJfM (ORCPT ); Tue, 15 Oct 2013 05:35:12 -0400 Received: from userp1040.oracle.com ([156.151.31.81]:30778 "EHLO userp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752589Ab3JOJfL (ORCPT ); Tue, 15 Oct 2013 05:35:11 -0400 Received: from ucsinet21.oracle.com (ucsinet21.oracle.com [156.151.31.93]) by userp1040.oracle.com (Sentrion-MTA-4.3.1/Sentrion-MTA-4.3.1) with ESMTP id r9F9Z5V6011701 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Tue, 15 Oct 2013 09:35:06 GMT Received: from userz7021.oracle.com (userz7021.oracle.com [156.151.31.85]) by ucsinet21.oracle.com (8.14.4+Sun/8.14.4) with ESMTP id r9F9Z4Da014017 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Tue, 15 Oct 2013 09:35:05 GMT Received: from abhmt118.oracle.com (abhmt118.oracle.com [141.146.116.70]) by userz7021.oracle.com (8.14.4+Sun/8.14.4) with ESMTP id r9F9Z4fY013998; Tue, 15 Oct 2013 09:35:04 GMT Received: from [10.182.37.92] (/10.182.37.92) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Tue, 15 Oct 2013 02:35:03 -0700 Message-ID: <525D0C41.2080407@oracle.com> Date: Tue, 15 Oct 2013 17:34:57 +0800 From: jianhai luan Organization: Oracle Corporation User-Agent: Mozilla/5.0 (Windows NT 5.1; rv:24.0) Gecko/20100101 Thunderbird/24.0.1 MIME-Version: 1.0 To: Ian Campbell CC: Wei Liu , xen-devel@lists.xenproject.org, netdev@vger.kernel.org, ANNIE LI Subject: Re: DomU's network interface will hung when Dom0 running 32bit References: <52590DFE.6080203@oracle.com> <20131014111958.GE11739@zion.uk.xensource.com> <525CAC21.5040202@oracle.com> <1381826609.24708.135.camel@kazak.uk.xensource.com> In-Reply-To: <1381826609.24708.135.camel@kazak.uk.xensource.com> X-Source-IP: ucsinet21.oracle.com [156.151.31.93] Sender: netdev-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On 2013-10-15 16:43, Ian Campbell wrote: > On Tue, 2013-10-15 at 10:44 +0800, jianhai luan wrote: >> On 2013-10-14 19:19, Wei Liu wrote: >>> On Sat, Oct 12, 2013 at 04:53:18PM +0800, jianhai luan wrote: >>>> Hi Ian, >>>> I meet the DomU's network interface hung issue recently, and have >>>> been working on the issue from that time. I find that DomU's network >>>> interface, which send lesser package, will hung if Dom0 running >>>> 32bit and DomU's up-time is very long. I think that one jiffies >>>> overflow bug exist in the function tx_credit_exceeded(). >>>> I know the inline function time_after_eq(a,b) will process jiffies >>>> overflow, but the function have one limit a should little that (b + >>>> MAX_SIGNAL_LONG). If a large than the value, time_after_eq will >>>> return false. The MAX_SINGNAL_LONG should be 0x7fffffff at 32-bit >>>> machine. >>>> If DomU's network interface send lesser package (<0.5k/s if >>>> jiffies=250 and credit_bytes=ULONG_MAX), jiffies will beyond out >>>> (credit_timeout.expires + MAX_SIGNAL_LONG) and time_after_eq(now, >>>> next_credit) will failure (should be true). So one timer which will >>>> not be trigger in short time, and later process will be aborted when >>>> timer_pending(&vif->credit_timeout) is true. The result will be >>>> DomU's network interface will be hung in long time (> 40days). >>>> Please think about the below scenario: >>>> Condition: >>>> Dom0 running 32-bit and HZ = 1000 >>>> vif->credit_timeout->expire = 0xffffffff, vif->remaining_credit >>>> = 0xffffffff, vif->credit_usec=0 jiffies=0 >>>> vif receive lesser package (DomU send lesser package). If the >>>> value is litter than 2K/s, consume 4G(0xffffffff) will need 582.55 >>>> hours. jiffies will large than 0x7ffffff. we guess jiffies = >>>> 0x800000ff, time_after_eq(0x800000ff, 0xffffffff) will failure, and >>>> one time which expire is 0xfffffff will be pended into system. So >>>> the interface will hung until jiffies recount 0xffffffff (that will >>>> need very long time). >>> If I'm not mistaken you meant time_after_eq(now, next_credit) in >>> netback. How does next_credit become 0xffffffff? >> I only assume the value is 0xfffffff, and the value of next_credit >> isn't point. If the delta between now and next_credit larger than >> ULONG_MAX, time_after_eq will do wrong judge. > So it sounds like we need a timer which is independent of the traffic > being sent to keep credit_timeout.expires rolling over. > > Can you propose a patch? Because credit_timeout.expire always after jiffies, i judge the value over the range of time_after_eq() by time_before(now, vif->credit_timeout.expires). please check the patch. > > Ian. > >>> Wei. >>> >>>> If some error exist in above explain, please help me point it out. >>>> >>>> Thanks, >>>> Jason > From f08c584ca1f393f6559b58b6b4c9e259c313259e Mon Sep 17 00:00:00 2001 From: Jason Luan Date: Tue, 15 Oct 2013 17:07:49 +0800 Subject: [PATCH] Process the wrong judge of time_after_eq(). If netfront send lesser package, the delta between now and next_credit will be out range of time_after_qe() and the function will do wrong judge. Because the expires always after jiffies, we judge the condition by time_before(now, vif->credit_timeout.expires). Signed-off-by: Jason Luan --- drivers/net/xen-netback/netback.c | 3 ++- 1 files changed, 2 insertions(+), 1 deletions(-) diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c index f3e591c..8036ce6 100644 --- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -1195,7 +1195,8 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size) return true; /* Passed the point where we can replenish credit? */ - if (time_after_eq(now, next_credit)) { + if (time_after_eq(now, next_credit) || + unlikely(time_before(now, vif->credit_timeout.expires))) { vif->credit_timeout.expires = now; tx_add_credit(vif); }