Subject: Re: [Xen-devel] DomU's network interface will hung when Dom0 running 32bit

From: annie li <[email-masked]>
Date: Wed, 16 Oct 2013 23:26:14 +0800

On 2013-10-16 23:04, jianhai luan wrote:
>
>  From ef02403a10173896c5c102f768741d0700b8a3a2 Mon Sep 17 00:00:00 2001
> From: Jason Luan<[email-masked]>
> Date: Tue, 15 Oct 2013 17:07:49 +0800
> Subject: [PATCH] xen-netback: pending timer only in the range [expire,
>   next_credit)
>
> The function time_after_eq() do correct judge in range of MAX_UNLONG/2.
> If net-front send lesser package, the delta between now and next_credit
> will out of the range and time_after_eq() will do wrong judge in result
> to net-front hung.  For example:
>      expire    next_credit    ....    next_credit+MAX_UNLONG/2    now
>      -----------------time increases this direction----------------->
>
> We should be add the environment which now beyond next_credit+MAX_UNLONG/2.
> Because the fact now mustn't before expire, time_before(now, expire) == true
> will show the environment.
>      time_after_eq(now, next_credit) || time_before (now, expire)
>      ==
>      !time_in_range_open(now, expire, next_credit)
>
> Signed-off-by: Jason Luan<[email-masked]>
> ---
>   drivers/net/xen-netback/netback.c |    2 +-
>   1 files changed, 1 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/net/xen-netback/netback.c b/drivers/net/xen-netback/netback.c
> index f3e591c..62492f0 100644
> --- a/drivers/net/xen-netback/netback.c
> +++ b/drivers/net/xen-netback/netback.c
> @@ -1195,7 +1195,7 @@ static bool tx_credit_exceeded(struct xenvif *vif, unsigned size)
>   		return true;
>   
>   	/* Passed the point where we can replenish credit? */

I think the comments above can be removed, and it is better to explain 
the if condition here briefly.

Thanks
Annie

> -	if (time_after_eq(now, next_credit)) {
> +	if (!time_in_range(now, vif->credit_timeout.expires, next_credit)) {
>   		vif->credit_timeout.expires = now;
>   		tx_add_credit(vif);
>   	}