linux-kernel - Re: [PATCH] xen-netfront: Delete rx_refill_timer in xennet_disconnect

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Message-ID: <1485803209.6360.111.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 30 Jan 2017 11:06:49 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Boris Ostrovsky <boris.ostrovsky@...cle.com>
Cc:     jgross@...e.com, xen-devel@...ts.xenproject.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        vineethp@...zon.com, wei.liu2@...rix.com, paul.durrant@...rix.com,
        stable@...r.kernel.org
Subject: Re: [PATCH] xen-netfront: Delete rx_refill_timer in
 xennet_disconnect_backend()

On Mon, 2017-01-30 at 13:23 -0500, Boris Ostrovsky wrote:

> We do netif_carrier_off() first thing in xennet_disconnect_backend() and
> the only place where the timer is rearmed is xennet_alloc_rx_buffers(),
> which is guarded by netif_carrier_ok() check.

Oh well, testing netif_carrier_ok() in packet processing fast path looks
unusual and a waste of cpu cycles. I've never seen that pattern before.

If one day, we remove this netif_carrier_ok() test during a cleanup,
then the race window will open again.