netdev - Re: [Xen-devel] [PATCH net V2] xen-netback: use jiffies

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Message-ID: <526E5042.7080406@cantab.net>
Date:	Mon, 28 Oct 2013 11:53:38 +0000
From:	David Vrabel <dvrabel@...tab.net>
To:	Wei Liu <wei.liu2@...rix.com>, xen-devel@...ts.xen.org,
	netdev@...r.kernel.org
CC:	Ian Campbell <ian.campbell@...rix.com>, annie.li@...cle.com,
	david.vrabel@...rix.com, jbeulich@...e.com,
	Jason Luan <jianhai.luan@...cle.com>
Subject: Re: [Xen-devel] [PATCH net V2] xen-netback: use jiffies_64 value
 to calculate credit timeout

On 28/10/2013 11:35, Wei Liu wrote:
> time_after_eq() only works if the delta is < MAX_ULONG/2.
> 
> For a 32bit Dom0, if netfront sends packets at a very low rate, the time
> between subsequent calls to tx_credit_exceeded() may exceed MAX_ULONG/2
> and the test for timer_after_eq() will be incorrect. Credit will not be
> replenished and the guest may become unable to send packets (e.g., if
> prior to the long gap, all credit was exhausted).
> 
> Use jiffies_64 variant to mitigate this problem for 32bit Dom0.

Reviewed-by: David Vrabel <david.vrabel@...rix.com>

David
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