Re: panic: Duplicate free of item 0xffffff005c4a8600 from zone 0xffffff007fed4780(Mbuf)

On Sun, 18 Jul 2004, Willem Jan Withagen wrote:

> Started running with debug.mpsafe=1.  Not shure if it has anything to do
> with it.... 

It might well do, but here are some things to try:

- See if you can reproduce this with your exact some configuration in a
  few runs.  If you can, then we should try some other configurations.

- Try it with debug.mpsafenet=0 and see if the problem "goes away" for a
  few runs.

- Try compiling IPv6 out of your kernel -- this will turn on the inpcb
  locking assertions, which are compiled out by default because IPv4 and
  IPv6 share the same underlying pcb code and IPv6 does not yet lock that
  correctly in CVS.  I have patches that do quite a bit of that in
  Perforce, and sent out an e-mail yesterday to the KAME folk to talk
  about merging strategies.

- If this is a reproduceable problem, could you try disabling SACK and see
  if it changes at all?

I'll do some review of the TCP reassembly and queue bits, it could well be
that we're missing some locking here.  Nicely configured system, btw. :-)

BTW, I noticed that there are some bge0 warnings at the end of the dmesg
-- is that indicative of some other problem with the driver on the system,
and/or is bge0 used in your active configuration?  Thanks for the nice
bundling of config information, btw -- it answered a number of my
questions up front quite nicely.

Thanks,

Robert N M Watson             FreeBSD Core Team, TrustedBSD Projects
robert_at_fledge.watson.org      Principal Research Scientist, McAfee Research


> 
> While running configure over NFS:
> 
> Slab at 0xffffff005c4a8fb8, freei 6 = 0.
> panic: Duplicate free of item 0xffffff005c4a8600 from zone 0xffffff007fed4780(Mb
> uf)
> 
> cpuid = 1;
> KDB: stack backtrace:
> kdb_backtrace() at kdb_backtrace+0x34
> panic() at panic+0x1d2
> uma_dbg_free() at uma_dbg_free+0x112
> uma_zfree_arg() at uma_zfree_arg+0x10a
> mb_free_ext() at mb_free_ext+0x96
> m_freem() at m_freem+0x28
> tcp_reass() at tcp_reass+0x1bb
> tcp_input() at tcp_input+0x2af9
> ip_input() at ip_input+0x94c
> netisr_processqueue() at netisr_processqueue+0x8c
> swi_net() at swi_net+0xe8
> ithread_loop() at ithread_loop+0x18d
> fork_exit() at fork_exit+0xc9
> fork_trampoline() at fork_trampoline+0xe
> --- trap 0, rip = 0, rsp = 0xffffffffb0bb5d00, rbp = 0 ---
> KDB: enter: panic
> [thread 100017]
> Stopped at      kdb_enter+0x2e: nop
> 
> Coredump available.... 61Mb compressed.
> 
> system contains a de card, which is correctly identified as
> GIANT-LOCKED. The card is not connected. Next time I open up the box,
> I'll remove it. 
> 
> system info available at: 
>     http://withagen.dyndns.org/FreeBSD/cores/*.opteron
> 
> --WjW
> 
>