netdev - Re: DomU's network interface will hung when Dom0 running 32bit

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Message-ID: <525D513B.70406@oracle.com>
Date:	Tue, 15 Oct 2013 22:29:15 +0800
From:	jianhai luan <jianhai.luan@...cle.com>
To:	Wei Liu <wei.liu2@...rix.com>
CC:	Ian Campbell <Ian.Campbell@...rix.com>,
	xen-devel@...ts.xenproject.org, netdev@...r.kernel.org,
	ANNIE LI <annie.li@...cle.com>
Subject: Re: DomU's network interface will hung when Dom0 running 32bit


On 2013-10-15 20:58, Wei Liu wrote:
> On Tue, Oct 15, 2013 at 07:26:31PM +0800, jianhai luan wrote:
> [...]
>>>>> 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.
>>> I don't think this really fix the issue for you. You still have chance
>>> that now wraps around and falls between expires and next_credit. In that
>>> case it's stalled again.
>> if time_before(now, vif->credit_timeout.expires) is true, time wrap
>> and do operation. Otherwise time_before(now,
>> vif->credit_timeout.expires) isn't true, now -
>> vif->credit_timeout.expires should be letter than ULONG_MAX/2.
>> Because next_credit large than vif->credit_timeout.expires
>> (next_crdit = vif->credit_timeout.expires +
>> msecs_to_jiffies(vif->credit_usec/1000)), the delta between now and
>> next_credit should be in range of time_after_eq().  So
>> time_after_eq() do correctly judge.
>>
> Not sure I understand you. Consider "now" is placed like this:
>
>     expires   now   next_credit
>     ----time increases this direction--->
>
> * time_after_eq(now, next_credit) -> false
> * time_before(now, expires) -> false

If now is placed in above environment, the result will be correct 
(Sending package will be not allowed until next_credit).
* time_after_eq(now, next_credit)  --> false will include two environment:
   expires     now   next_credit
   -----------time increases this direction ---->

Or
   expires      next_credit             next_credit + MAX_LONG/2 now
   -----------time increases this direction ---->


the first environment should be correct to control transmit. the second 
environment is our included environment.

Jason
>
> Then it's stuck again. You're merely narrowing the window, not fixing
> the real problem.
>
> Wei.
>
>> Jason
>>> Wei.

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