From: Zoltan Kiss Date: Tue, 4 Feb 2014 19:54:37 +0000 (+0000) Subject: xen-netback: Fix Rx stall due to race condition X-Git-Tag: v3.14-rc3~36^2~49 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=9ab9831b4c59d379a17f92a6157c7e921811dea2;p=pandora-kernel.git xen-netback: Fix Rx stall due to race condition 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 Reviewed-by: Paul Durrant Acked-by: Wei Liu Signed-off-by: David S. Miller --- Reading git-diff-tree failed