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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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