From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ian Campbell Subject: Re: DomU's network interface will hung when Dom0 running 32bit Date: Tue, 15 Oct 2013 09:43:29 +0100 Message-ID: <1381826609.24708.135.camel@kazak.uk.xensource.com> References: <52590DFE.6080203@oracle.com> <20131014111958.GE11739@zion.uk.xensource.com> <525CAC21.5040202@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit Cc: Wei Liu , , To: jianhai luan Return-path: Received: from smtp02.citrix.com ([66.165.176.63]:34251 "EHLO SMTP02.CITRIX.COM" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750965Ab3JOInc (ORCPT ); Tue, 15 Oct 2013 04:43:32 -0400 In-Reply-To: <525CAC21.5040202@oracle.com> Sender: netdev-owner@vger.kernel.org List-ID: 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? Ian. > > > > Wei. > > > >> If some error exist in above explain, please help me point it out. > >> > >> Thanks, > >> Jason >