Messages in this thread | | | Date | Tue, 2 Mar 2010 16:16:59 +0300 | Subject | Re: Panic at tcp_xmit_retransmit_queue | From | sbs <> |
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thank you very much, have stable running server for a week and it seems that it works like a charm now, i havent detected any panics since i apply the patch. although seems that the problem stops ocurring cause i dont see any debug information through netconsole
On Mon, Feb 15, 2010 at 4:21 PM, Ilpo Järvinen <ilpo.jarvinen@helsinki.fi> wrote: > On Wed, 3 Feb 2010, Ilpo Järvinen wrote: > >> On Mon, 1 Feb 2010, sbs wrote: >> >> > actually removing netconsole from kernel didnt help. >> > i found many guys with the same problem but with different hardware >> > configurations here: >> > >> > freez in TCP stack : >> > http://bugzilla.kernel.org/show_bug.cgi?id=14470 >> > >> > is there someone who can investigate it? >> > >> > >> > On Tue, Jan 19, 2010 at 7:13 PM, sbs <gexlie@gmail.com> wrote: >> > > We are hiting kernel panics on servers with nVidia MCP55 NICs once a day; >> > > it appears usualy under a high network trafic ( around 10000Mbit/s) but >> > > it is not a rule, it has happened even on low trafic. >> > > >> > > Servers are used as nginx+static content >> > > On 2 equal servers this panic happens aprox 2 times a day depending on >> > > network load. Machine completly freezes till the netconsole reboots. >> > > >> > > Kernel: 2.6.32.3 >> > > >> > > what can it be? whats wrong with tcp_xmit_retransmit_queue() function ? >> > > can anyone explain or fix? >> >> You might want to try with to debug patch below. It might even make the >> box to survive the event (if I got it coded right). > > Here should be a better version of the debug patch, hopefully the infinite > looping is now gone. > > -- > i. > > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c > index 383ce23..4672a30 100644 > --- a/net/ipv4/tcp_output.c > +++ b/net/ipv4/tcp_output.c > @@ -2186,6 +2186,42 @@ static int tcp_can_forward_retransmit(struct sock *sk) > return 1; > } > > +static void print_queue(struct sock *sk, struct sk_buff *old, struct sk_buff *hole) > +{ > + struct tcp_sock *tp = tcp_sk(sk); > + struct sk_buff *skb, *prev; > + > + skb = tcp_write_queue_head(sk); > + prev = (struct sk_buff *)(&sk->sk_write_queue); > + > + if (skb == NULL) { > + printk("NULL head, pkts %u\n", tp->packets_out); > + return; > + } > + printk("head %p tail %p sendhead %p oldhint %p now %p hole %p high %u\n", > + tcp_write_queue_head(sk), tcp_write_queue_tail(sk), > + tcp_send_head(sk), old, tp->retransmit_skb_hint, hole, > + tp->retransmit_high); > + > + while (skb) { > + printk("skb %p (%u-%u) next %p prev %p sacked %u\n", > + skb, TCP_SKB_CB(skb)->seq, TCP_SKB_CB(skb)->end_seq, > + skb->next, skb->prev, TCP_SKB_CB(skb)->sacked); > + if (prev != skb->prev) > + printk("Inconsistent prev\n"); > + > + if (skb == tcp_write_queue_tail(sk)) { > + if (skb->next != (struct sk_buff *)(&sk->sk_write_queue)) > + printk("Improper next at tail\n"); > + return; > + } > + > + prev = skb; > + skb = skb->next; > + } > + printk("Encountered unexpected NULL\n"); > +} > + > /* This gets called after a retransmit timeout, and the initially > * retransmitted data is acknowledged. It tries to continue > * resending the rest of the retransmit queue, until either > @@ -2194,12 +2230,15 @@ static int tcp_can_forward_retransmit(struct sock *sk) > * based retransmit packet might feed us FACK information again. > * If so, we use it to avoid unnecessarily retransmissions. > */ > +static int caught_it = 0; > + > void tcp_xmit_retransmit_queue(struct sock *sk) > { > const struct inet_connection_sock *icsk = inet_csk(sk); > struct tcp_sock *tp = tcp_sk(sk); > struct sk_buff *skb; > struct sk_buff *hole = NULL; > + struct sk_buff *old = tp->retransmit_skb_hint; > u32 last_lost; > int mib_idx; > int fwd_rexmitting = 0; > @@ -2217,6 +2256,16 @@ void tcp_xmit_retransmit_queue(struct sock *sk) > last_lost = tp->snd_una; > } > > +checknull: > + if (skb == NULL) { > + if (!caught_it) > + print_queue(sk, old, hole); > + caught_it++; > + if (net_ratelimit()) > + printk("Errors caught so far %u\n", caught_it); > + return; > + } > + > tcp_for_write_queue_from(skb, sk) { > __u8 sacked = TCP_SKB_CB(skb)->sacked; > > @@ -2257,7 +2306,7 @@ begin_fwd: > } else if (!(sacked & TCPCB_LOST)) { > if (hole == NULL && !(sacked & (TCPCB_SACKED_RETRANS|TCPCB_SACKED_ACKED))) > hole = skb; > - continue; > + goto cont; > > } else { > last_lost = TCP_SKB_CB(skb)->end_seq; > @@ -2268,7 +2317,7 @@ begin_fwd: > } > > if (sacked & (TCPCB_SACKED_ACKED|TCPCB_SACKED_RETRANS)) > - continue; > + goto cont; > > if (tcp_retransmit_skb(sk, skb)) > return; > @@ -2278,6 +2327,9 @@ begin_fwd: > inet_csk_reset_xmit_timer(sk, ICSK_TIME_RETRANS, > inet_csk(sk)->icsk_rto, > TCP_RTO_MAX); > +cont: > + skb = skb->next; > + goto checknull; > } > } > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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