Date: Tue, 23 Nov 2004 01:16:02 +0100 (CET) From: Sten Spans <sten@blinkenlights.nl> To: John Baldwin <jhb@FreeBSD.org> Cc: freebsd-alpha@FreeBSD.org Subject: Re: alpha and em mtu Message-ID: <Pine.SOC.4.61.0411230026430.10997@tea.blinkenlights.nl> In-Reply-To: <200411221711.54916.jhb@FreeBSD.org> References: <Pine.SOC.4.61.0411142153430.26307@tea.blinkenlights.nl> <Pine.SOC.4.61.0411222147180.10997@tea.blinkenlights.nl> <200411221711.54916.jhb@FreeBSD.org>
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On Mon, 22 Nov 2004, John Baldwin wrote:
> On Monday 22 November 2004 04:15 pm, Sten Spans wrote:
>>
>> db> trace
>> tcp_input() at tcp_input+0x3a4
>> ip_input() at ip_input+0x9fc
>> netisr_processqueue() at netisr_processqueue+0xac
>> swi_net() at swi_net+0xf0
>> ithread_loop() at ithread_loop+0x1d4
>> fork_exit() at fork_exit+0x100
>> exception_return() at exception_return
>> --- root of call graph ---
>>
>> (gdb) l *tcp_input+0x3a4
>> 0xfffffc00004cd054 is in tcp_input (/usr/src/sys/netinet/tcp_input.c:554).
>> 549
>> 550 /*
>> 551 * Check that TCP offset makes sense,
>> 552 * pull out TCP options and adjust length.
>> XXX
>> 553 */
>> 554 off = th->th_off << 2;
>> 555 if (off < sizeof (struct tcphdr) || off > tlen) {
>> 556 tcpstat.tcps_rcvbadoff++;
>> 557 goto drop;
>> 558 }
>> (gdb) l *ip_input+0x9fc
>> 0xfffffc00004c355c is in ip_input (/usr/src/sys/netinet/ip_input.c:739).
>> 734 /*
>> 735 * Switch out to protocol's input routine.
>> 736 */
>> 737 ipstat.ips_delivered++;
>> 738
>> 739 (*inetsw[ip_protox[ip->ip_p]].pr_input)(m, hlen);
>> 740 return;
>> 741 bad:
>> 742 m_freem(m);
>> 743 }
>> (gdb) l *netisr_processqueue+0xac
>> 0xfffffc00004ad45c is in netisr_processqueue
>> (/usr/src/sys/net/netisr.c:233).
>> 228
>> 229 for (;;) {
>> 230 IF_DEQUEUE(ni->ni_queue, m);
>> 231 if (m == NULL)
>> 232 break;
>> 233 ni->ni_handler(m);
>> 234 }
>> 235 }
>
> Hmm, so can you check here to see if the 'm' pointer in this routine is
> misaligned? If so, then this may be a driver bug.
>
--- netisr.c.orig Tue Nov 23 00:21:38 2004
+++ netisr.c Tue Nov 23 00:21:45 2004
@@ -230,6 +230,8 @@
IF_DEQUEUE(ni->ni_queue, m);
if (m == NULL)
break;
+ if (((uintptr_t)m & 0x3) != 0)
+ printf("%s: mbuf %p is misaligned\n", __func__, m);
ni->ni_handler(m);
}
}
doesn't seem to print anything, but ...
if_em.c
2442
2443 /*if (ifp->if_mtu <= ETHERMTU) { */
2444 m_adj(mp, ETHER_ALIGN);
2445 /*} */
2446
does seem to fix the crash, also trashes the performance,
but that's another matter. It looks like mbuf alignment is
needed, if_bge seems to provide reasonable examples.
--
Sten Spans
"There is a crack in everything, that's how the light gets in."
Leonard Cohen - Anthem
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