Messages in this thread | | | Date | Tue, 24 Mar 2009 16:29:03 +0100 | From | Sascha Hauer <> | Subject | Re: Revert "gro: Fix legacy path napi_complete crash", (was: Re: Linux 2.6.29) |
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On Tue, Mar 24, 2009 at 11:09:28PM +0800, Herbert Xu wrote: > On Tue, Mar 24, 2009 at 03:39:42PM +0100, Ingo Molnar wrote: > > > > Subject: [PATCH] net: Fix netpoll lockup in legacy receive path > > Actually, this patch is still racy. If some interrupt comes in > and we suddenly get the maximum amount of backlog we can still > hang when we call __napi_complete incorrectly. It's unlikely > but we certainly shouldn't allow that. Here's a better version.
Yes, this one works. I always wanted to give a
Tested-by: Sascha Hauer <s.hauer@pengutronix.de>
Thanks Sascha
> > 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. > > What's more, we really do need to keep the __napi_complete call > within the IRQ-off section since in theory an IRQ can occur in > between and fill up the backlog to the maximum, causing us to > lock up. > > This patch fixes this by essentially open-coding __napi_complete. > > Note we no longer need the memory barrier because this function > is per-cpu. > > Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au> > > diff --git a/net/core/dev.c b/net/core/dev.c > index e3fe5c7..2a7f6b3 100644 > --- a/net/core/dev.c > +++ b/net/core/dev.c > @@ -2588,9 +2588,10 @@ static int process_backlog(struct napi_struct *napi, int quota) > local_irq_disable(); > skb = __skb_dequeue(&queue->input_pkt_queue); > if (!skb) { > + list_del(&napi->poll_list); > + clear_bit(NAPI_STATE_SCHED, &napi->state); > local_irq_enable(); > - napi_complete(napi); > - goto out; > + break; > } > local_irq_enable(); > > @@ -2599,7 +2600,6 @@ static int process_backlog(struct napi_struct *napi, int quota) > > napi_gro_flush(napi); > > -out: > return work; > } > > Thanks, > -- > Visit Openswan at http://www.openswan.org/ > Email: Herbert Xu ~{PmV>HI~} <herbert@gondor.apana.org.au> > Home Page: http://gondor.apana.org.au/~herbert/ > PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt >
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