[ 27/89] net-rps: Fix brokeness causing OOO packets

[Ben Hutchings]

3.2-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Tom Herbert <therbert@xxxxxxxxxx>

[ Upstream commit baefa31db2f2b13a05d1b81bdf2d20d487f58b0a ]

In commit c445477d74ab3779 which adds aRFS to the kernel, the CPU
selected for RFS is not set correctly when CPU is changing.
This is causing OOO packets and probably other issues.

Signed-off-by: Tom Herbert <therbert@xxxxxxxxxx>
Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>
Acked-by: Ben Hutchings <bhutchings@xxxxxxxxxxxxxx>
Signed-off-by: David S. Miller <davem@xxxxxxxxxxxxx>
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 net/core/dev.c | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index 480be72..2aac4ec 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2829,8 +2829,10 @@ static int get_rps_cpu(struct net_device *dev, struct sk_buff *skb,
 		if (unlikely(tcpu != next_cpu) &&
 		    (tcpu == RPS_NO_CPU || !cpu_online(tcpu) ||
 		     ((int)(per_cpu(softnet_data, tcpu).input_queue_head -
-		      rflow->last_qtail)) >= 0))
+		      rflow->last_qtail)) >= 0)) {
+			tcpu = next_cpu;
 			rflow = set_rps_cpu(dev, skb, rflow, next_cpu);
+		}
 
 		if (tcpu != RPS_NO_CPU && cpu_online(tcpu)) {
 			*rflowp = rflow;


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