Re: [PATCH] xen-netfront: Delete rx_refill_timer in xennet_disconnect_backend()

From	Boris Ostrovsky <boris.ostrovsky@oracle.com>
Newsgroups	linux.kernel
Subject	Re: [PATCH] xen-netfront: Delete rx_refill_timer in xennet_disconnect_backend()
Date	2017-01-30 20:40 +0100
Message-ID	<t5pXY-7V1-7@gated-at.bofh.it> (permalink)
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On 01/30/2017 02:06 PM, Eric Dumazet wrote:
> 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.

I don't know much about napi but I wonder whether I can indeed disable
it in xennet_disconnect_backend(). I don't see how anything can happen
after disconnect since it unmaps the rings. And then napi is re-enabled
during reconnection in xennet_create_queues(). In which case am not sure
there is any need for xennet_destroy_queues() as everything there could
be folded into xennet_disconnect_backend().

-boris

Thread

[PATCH] xen-netfront: Delete rx_refill_timer in xennet_disconnect_backend() Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-01-30 19:00 +0100
  Re: [PATCH] xen-netfront: Delete rx_refill_timer in  xennet_disconnect_backend() Eric Dumazet <eric.dumazet@gmail.com> - 2017-01-30 19:10 +0100
    Re: [PATCH] xen-netfront: Delete rx_refill_timer in  xennet_disconnect_backend() Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-01-30 19:30 +0100
      Re: [PATCH] xen-netfront: Delete rx_refill_timer in  xennet_disconnect_backend() Eric Dumazet <eric.dumazet@gmail.com> - 2017-01-30 20:10 +0100
        Re: [PATCH] xen-netfront: Delete rx_refill_timer in  xennet_disconnect_backend() Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-01-30 20:40 +0100
          Re: [PATCH] xen-netfront: Delete rx_refill_timer in  xennet_disconnect_backend() Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-01-31 18:50 +0100
            Re: [PATCH] xen-netfront: Delete rx_refill_timer in  xennet_disconnect_backend() Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-02-02 00:30 +0100
              Re: [PATCH] xen-netfront: Delete rx_refill_timer in  xennet_disconnect_backend() Eric Dumazet <eric.dumazet@gmail.com> - 2017-02-02 01:10 +0100
  Re: [PATCH] xen-netfront: Delete rx_refill_timer in  xennet_disconnect_backend() Juergen Gross <jgross@suse.com> - 2017-02-03 10:40 +0100
    Re: [PATCH] xen-netfront: Delete rx_refill_timer in  xennet_disconnect_backend() Boris Ostrovsky <boris.ostrovsky@oracle.com> - 2017-02-09 14:50 +0100
      Re: [PATCH] xen-netfront: Delete rx_refill_timer in  xennet_disconnect_backend() David Miller <davem@davemloft.net> - 2017-02-10 20:00 +0100

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