From mboxrd@z Thu Jan 1 00:00:00 1970 From: annie li Subject: Re: DomU's network interface will hung when Dom0 running 32bit Date: Wed, 16 Oct 2013 15:10:20 +0800 Message-ID: <525E3BDC.4060309@oracle.com> References: <52590DFE.6080203@oracle.com> <20131014111958.GE11739@zion.uk.xensource.com> <525CAC21.5040202@oracle.com> <1381826609.24708.135.camel@kazak.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Cc: jianhai luan , Wei Liu , xen-devel@lists.xenproject.org, netdev@vger.kernel.org To: Ian Campbell Return-path: Received: from aserp1040.oracle.com ([141.146.126.69]:35781 "EHLO aserp1040.oracle.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1759887Ab3JPHKa (ORCPT ); Wed, 16 Oct 2013 03:10:30 -0400 In-Reply-To: <1381826609.24708.135.camel@kazak.uk.xensource.com> Sender: netdev-owner@vger.kernel.org List-ID: 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. Resending it because of the wrong format in last email... Is it a timer to be set as less than ULONG_MAX/2 to avoid credit_timeout.expires rolling over? But the problem is that we can not assure where jiffies start from, and this probably results into current issue again. I assume Jason's patch fix this issue and this patch only uses __mod_timer to add a timer with next_credit when the netback fails to send out current available credits. Thanks Annie > > Can you propose a patch? > > Ian. > >>> Wei. >>> >>>> If some error exist in above explain, please help me point it out. >>>> >>>> Thanks, >>>> Jason > > -- > To unsubscribe from this list: send the line "unsubscribe netdev" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html