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    SubjectRe: Revert "gro: Fix legacy path napi_complete crash", (was: Re: Linux 2.6.29)

    * Robert Schwebel <r.schwebel@pengutronix.de> wrote:

    > On Tue, Mar 24, 2009 at 02:02:02PM +0100, Ingo Molnar wrote:
    > > If the box hung within 15 minutes, the kernel was deemed bad. Using
    > > that method i arrived to this upstream networking fix which was
    > > merged yesterday:
    > >
    > > | 303c6a0251852ecbdc5c15e466dcaff5971f7517 is first bad commit
    > > | commit 303c6a0251852ecbdc5c15e466dcaff5971f7517
    > > | Author: Herbert Xu <herbert@gondor.apana.org.au>
    > > | Date: Tue Mar 17 13:11:29 2009 -0700
    > > |
    > > | gro: Fix legacy path napi_complete crash
    >
    > This commit breaks nfsroot booting on i.MX27 and other ARM boxes
    > with different network cards here in a reproducable way.

    Can you confirm that Herbert's fix (see it below) solves the
    problem?

    Ingo

    --------------->
    From b8b66ac07cab1b45aac93e4f406833a1e0d7677e Mon Sep 17 00:00:00 2001
    From: Herbert Xu <herbert@gondor.apana.org.au>
    Date: Tue, 24 Mar 2009 21:35:42 +0800
    Subject: [PATCH] net: Fix netpoll lockup in legacy receive path

    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@gondor.apana.org.au>
    Cc: Linus Torvalds <torvalds@linux-foundation.org>
    Cc: Frank Blaschka <blaschka@linux.vnet.ibm.com>
    Cc: "David S. Miller" <davem@davemloft.net>
    Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
    LKML-Reference: <20090324133542.GA29046@gondor.apana.org.au>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    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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