netdev - Re: [Xen-devel] [PATCH net] xen-netback: add the scenario which now beyond the range time_after

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Message-ID: <20131017140611.GM16371@zion.uk.xensource.com>
Date:	Thu, 17 Oct 2013 15:06:11 +0100
From:	Wei Liu <wei.liu2@...rix.com>
To:	jianhai luan <jianhai.luan@...cle.com>
CC:	David Vrabel <david.vrabel@...rix.com>,
	Jan Beulich <JBeulich@...e.com>, <ian.campbell@...rix.com>,
	<wei.liu2@...rix.com>, <xen-devel@...ts.xenproject.org>,
	<annie.li@...cle.com>, <netdev@...r.kernel.org>
Subject: Re: [Xen-devel] [PATCH net] xen-netback: add the scenario which now
 beyond the range time_after_eq().

On Thu, Oct 17, 2013 at 09:59:30PM +0800, jianhai luan wrote:
[...]
> >>>>If use time_after_eq64(), expire ,next_credit and other member will must
> >>>>be u64.
> >>>Yes, you'll need to store next_credit as a u64 in vif instead of
> >>>calculating it in tx_credit_exceeded from expires (which is only an
> >>>unsigned long).
> >>I know that.  Even we use u64, time_after_eq()  will also do wrong judge
> >>in theory (not in reality because need long long time).
> >If jiffies_64 has millisecond resolution that would be more than
> >500,000,000 years.
> 
> Yes, I agree the fact.
> >
> >>I think the two better fixed way is below:
> >>   - By time_before() to judge if now beyond MAX_ULONG/2
> >This is broken, so no.
> 
> Where is broken?  would you like to help me point it out.

I think David means you didn't actually fix the problem. Your solution is
merely a workaround.

> >
> >David
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