[PATCH] net: Fix netpoll lockup in legacy receive path

[Herbert Xu]

When I fixed the GRO crash in the legacy receive path I used
napi_complete to replace __napi_complete.  Unfortunately they're
not the same when NETPOLL is enabled, which may result in us
not calling __napi_complete at all.

While this is fishy in itself, let's make the obvious fix right
now of reverting to the previous state where we always called
__napi_complete.

Signed-off-by: Herbert Xu <herbert@xxxxxxxxxxxxxxxxxxx>
Cc: Linus Torvalds <torvalds@xxxxxxxxxxxxxxxxxxxx>
Cc: Frank Blaschka <blaschka@xxxxxxxxxxxxxxxxxx>
Cc: "David S. Miller" <davem@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
LKML-Reference: <20090324133542.GA29046@xxxxxxxxxxxxxxxxxxx>
Signed-off-by: Ingo Molnar <mingo@xxxxxxx>
---
 net/core/dev.c |   16 +++++++++-------
 1 files changed, 9 insertions(+), 7 deletions(-)

diff --git a/net/core/dev.c b/net/core/dev.c
index e3fe5c7..523f53e 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2580,24 +2580,26 @@ static int process_backlog(struct napi_struct *napi, int quota)
 	int work = 0;
 	struct softnet_data *queue = &__get_cpu_var(softnet_data);
 	unsigned long start_time = jiffies;
+	struct sk_buff *skb;
 
 	napi->weight = weight_p;
 	do {
-		struct sk_buff *skb;
-
 		local_irq_disable();
 		skb = __skb_dequeue(&queue->input_pkt_queue);
-		if (!skb) {
-			local_irq_enable();
-			napi_complete(napi);
-			goto out;
-		}
 		local_irq_enable();
+		if (!skb)
+			break;
 
 		napi_gro_receive(napi, skb);
 	} while (++work < quota && jiffies == start_time);
 
 	napi_gro_flush(napi);
+	if (skb)
+		goto out;
+
+	local_irq_disable();
+	__napi_complete(napi);
+	local_irq_enable();
 
 out:
 	return work;
--
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