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Date: Wed, 05 Feb 2014 16:24:22 -0800 (PST) From: David Miller <davem@...hat.com> To: zoltan.kiss@...rix.com Cc: ian.campbell@...rix.com, wei.liu2@...rix.com, xen-devel@...ts.xenproject.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, jonathan.davies@...rix.com Subject: Re: [PATCH net v3] xen-netback: Fix Rx stall due to race condition From: Zoltan Kiss <zoltan.kiss@...rix.com> Date: Tue, 4 Feb 2014 19:54:37 +0000 > The recent patch to fix receive side flow control > (11b57f90257c1d6a91cee720151b69e0c2020cf6: xen-netback: stop vif thread > spinning if frontend is unresponsive) solved the spinning thread problem, > however caused an another one. The receive side can stall, if: > - [THREAD] xenvif_rx_action sets rx_queue_stopped to true > - [INTERRUPT] interrupt happens, and sets rx_event to true > - [THREAD] then xenvif_kthread sets rx_event to false > - [THREAD] rx_work_todo doesn't return true anymore > > Also, if interrupt sent but there is still no room in the ring, it take quite a > long time until xenvif_rx_action realize it. This patch ditch that two variable, > and rework rx_work_todo. If the thread finds it can't fit more skb's into the > ring, it saves the last slot estimation into rx_last_skb_slots, otherwise it's > kept as 0. Then rx_work_todo will check if: > - there is something to send to the ring (like before) > - there is space for the topmost packet in the queue > > I think that's more natural and optimal thing to test than two bool which are > set somewhere else. > > Signed-off-by: Zoltan Kiss <zoltan.kiss@...rix.com> > Reviewed-by: Paul Durrant <paul.durrant@...rix.com> > Acked-by: Wei Liu <wei.liu2@...rix.com> Applied, thanks. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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