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Date: Mon, 30 Jan 2017 14:31:58 -0500 From: Boris Ostrovsky <boris.ostrovsky@...cle.com> To: Eric Dumazet <eric.dumazet@...il.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 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
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