help w/panic under heavy load - 5.4

Edwin edwin at
Tue Jul 19 20:46:49 GMT 2005

Hi John,

Re-compiled with INVARIANTS/INVARIANT_SUPPORT included the gdb output below - same situation (put heavy load 
on the box - incidentally - small (68 byte UDP packets) - fwiw.

my buildkernel kept failing on the options DDB (even tried GENERIC kernel) - so I'm 
sure I'm doing something wrong there - just didn't figure it out yet.

I wanted to get back to you with the output for the above asap though - I'm happy to input/output whatever commands
you would like if necc.


mbsd05# kgdb kernel.debug /tmp/crash/vmcore.5
[GDB will not be able to debug user-mode threads: /usr/lib/ Undefined symbol "ps_pglobal_lookup"]
GNU gdb 6.1.1 [FreeBSD]
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welcome to change it and/or distribute copies of it under certain conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for details.
This GDB was configured as "i386-marcel-freebsd".
#0  doadump () at pcpu.h:159
159             __asm __volatile("movl %%fs:0,%0" : "=r" (td));
(kgdb) where
#0  doadump () at pcpu.h:159
#1  0xc060c474 in boot (howto=260) at /usr/src/sys/kern/kern_shutdown.c:410
#2  0xc060c6f2 in panic (fmt=0xc081e5ad "m_copym, offset > size of mbuf chain") at /usr/src/sys/kern/kern_shutdown.c:566
#3  0xc063beb8 in m_copym (m=0x0, off0=1500, len=1480, wait=1) at /usr/src/sys/kern/uipc_mbuf.c:385
#4  0xc06996b4 in ip_fragment (ip=0xc124400e, m_frag=0xc7692c38, mtu=-1056768768, if_hwassist_flags=0, sw_csum=1)
    at /usr/src/sys/netinet/ip_output.c:967
#5  0xc069132e in ip_fastforward (m=0xc120e700) at /usr/src/sys/netinet/ip_fastfwd.c:572
#6  0xc066cd99 in ether_demux (ifp=0xc0f90000, m=0xc120e700) at /usr/src/sys/net/if_ethersubr.c:770
#7  0xc066cb1d in ether_input (ifp=0xc0f90000, m=0xc120e700) at /usr/src/sys/net/if_ethersubr.c:631
#8  0xc0711597 in sis_rxeof (sc=0xc0f90000) at /usr/src/sys/pci/if_sis.c:1636
#9  0xc071185f in sis_poll (ifp=0xc0f90000, cmd=POLL_ONLY, count=0) at /usr/src/sys/pci/if_sis.c:1769
#10 0xc05f2f5c in netisr_poll () at /usr/src/sys/kern/kern_poll.c:384
#11 0xc0673cc5 in swi_net (dummy=0x0) at /usr/src/sys/net/netisr.c:338
#12 0xc05fb10c in ithread_loop (arg=0xc0ec6480) at /usr/src/sys/kern/kern_intr.c:547
#13 0xc05fa580 in fork_exit (callout=0xc05fafe8 <ithread_loop>, arg=0xc0ec6480, frame=0xc7692d48)
    at /usr/src/sys/kern/kern_fork.c:791
#14 0xc07a26cc in fork_trampoline () at /usr/src/sys/i386/i386/exception.s:209
(kgdb) f 4
#4  0xc06996b4 in ip_fragment (ip=0xc124400e, m_frag=0xc7692c38, mtu=-1056768768, if_hwassist_flags=0, sw_csum=1)
    at /usr/src/sys/netinet/ip_output.c:967
967                     m->m_next = m_copy(m0, off, len);
(kgdb) f 3
#3  0xc063beb8 in m_copym (m=0x0, off0=1500, len=1480, wait=1) at /usr/src/sys/kern/uipc_mbuf.c:385
385                     KASSERT(m != NULL, ("m_copym, offset > size of mbuf chain"));
(kgdb) quit

John Baldwin (jhb at wrote:
> On Monday 18 July 2005 11:42 pm, Edwin wrote:
> > Hi,
> >
> > I have a recurring (re-producible) panic on the 5.3/5.4 kernels and I would
> > like to ask for some help in tracking it down. :) - it could be some
> > misconfig on my part - but i have tried several different configs of the
> > kernel - ultimately w/ polling on/off, ipfw on/off, ipfastforwarding on/off
> > - although with ipff off - the box still crashes but in a different
> > location - it will even crash w/ GENERIC kernel under heavy load.
> >
> > I'm not quite sure where to look past the below (ie. what variables/etc to
> > present to the list).
> Try turning INVARIANTS and INVARIANT_SUPPORT on in your kernel and see if you 
> can reproduce this.  Also, try to get a traceback in ddb if possible as 
> sometimes ddb gives more reliable stack traces.  It looks like your m is 
> NULL, in which case the KASSERT() on the previous line should fire if 
> -- 
> John Baldwin <jhb at>  <><
> "Power Users Use the Power to Serve"  =

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