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SubjectRe: Revert "gro: Fix legacy path napi_complete crash",
Herbert Xu wrote, On 03/25/2009 01:26 PM:

> On Wed, Mar 25, 2009 at 01:20:46PM +0100, Ingo Molnar wrote:
>> ok - i have started testing the delta below, on top of the plain
>> revert.
>
> Thanks! BTW Ingo, any chance you could help us identify the problem
> with the previous patch? I don't have a forcedeth machine here
> and the hang you had with my patch that open-coded __napi_complete
> appears intimately connected to forcedeth (with NAPI enabled).

Of course it's too late for verifying this now, but (for the future)
I think, this scenario could be considered:

process_backlog() netif_rx()

if (!skb)
local_irq_enable()
if (queue.qlen) //NO
napi_schedule() //NOTHING
__skb_queue_tail() //qlen > 0
napi_complete()
... ...
Every next netif_rx() sees
qlen > 0, so napi is never
scheduled again.
Then, something like this might work...

Jarek P.
--- (2.6.29)
net/core/dev.c | 6 +++++-
1 files changed, 5 insertions(+), 1 deletions(-)
diff --git a/net/core/dev.c b/net/core/dev.c
index e3fe5c7..cf53c24 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -2589,7 +2589,11 @@ static int process_backlog(struct napi_struct *napi, int quota)
skb = __skb_dequeue(&queue->input_pkt_queue);
if (!skb) {
local_irq_enable();
- napi_complete(napi);
+ napi_gro_flush(napi);
+ local_irq_disable();
+ if (skb_queue_empty(&queue->input_pkt_queue))
+ __napi_complete(napi);
+ local_irq_enable();
goto out;
}
local_irq_enable();

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