Messages in this thread | | | Date | Tue, 24 Mar 2009 16:22:00 +0100 | From | Sascha Hauer <> | Subject | Re: Revert "gro: Fix legacy path napi_complete crash", (was: Re: Linux 2.6.29) |
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Hi Ingo,
On Tue, Mar 24, 2009 at 03:39:42PM +0100, Ingo Molnar wrote: > > * 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?
No, still doesn't work.
It seems to have something to do with enabling interrupts between __skb_dequeue() and __napi_complete().
I reverted 303c6a0251852ecbdc5c15e466dcaff5971f7517 and added a
local_irq_enable(); local_irq_disable();
right before __napi_complete() and this already breaks networking.
Sascha
> > 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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