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SubjectRe: [PATCH v2] xen-netfront: Fix Rx stall during network stress and OOM
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From: Vineeth Remanan Pillai <vineethp@amazon.com>
Date: Thu, 19 Jan 2017 08:35:39 -0800

> From: Vineeth Remanan Pillai <vineethp@amazon.com>
>
> During an OOM scenario, request slots could not be created as skb
> allocation fails. So the netback cannot pass in packets and netfront
> wrongly assumes that there is no more work to be done and it disables
> polling. This causes Rx to stall.
>
> The issue is with the retry logic which schedules the timer if the
> created slots are less than NET_RX_SLOTS_MIN. The count of new request
> slots to be pushed are calculated as a difference between new req_prod
> and rsp_cons which could be more than the actual slots, if there are
> unconsumed responses.
>
> The fix is to calculate the count of newly created slots as the
> difference between new req_prod and old req_prod.
>
> Signed-off-by: Vineeth Remanan Pillai <vineethp@amazon.com>
> Reviewed-by: Juergen Gross <jgross@suse.com>
> ---
> Changes in v2:
> - Removed the old implementation of enabling polling on
> skb allocation error.
> - Corrected the refill timer logic to schedule when newly
> created slots since last push is less than NET_RX_SLOTS_MIN.

Applied.

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