Boot panic -CURRENT #196643

Hello,

I synced the sources today to #196643.
And built a kernel with WITNESS etc. off.

My boot partition sits on zfs.

I get the below panic. Unfortunately I can't bt since the usb keyboard 
ist not functional at this moment.

---
Trying to mount root from zfs:zroot
spin lock 0x80dccc00 (sched lock 1) held by 0x8595baf0 (tid 100003) too long
panic: spin lock held too long
cpuid = 0
KDB: enter: panic
[thread pid 1 tid 100002 ]
Stopped at	kdb_enter+0x3a: movl	$0,kdb_why
---

Unfortunately I can't say exactly which version the previous, working, 
kernel has. The svn nbr has gone. (I have this subversion:
subversion-freebsd-1.6.5)

Here the top of the dmesg:

FreeBSD 9.0-CURRENT #0: Fri Aug 28 21:05:42 CEST 2009
     andreast_at_tc.andreas.nets:/usr/obj/export/devel/fbsd/head/src/sys/TC
Timecounter "i8254" frequency 1193182 Hz quality 0
CPU: Intel(R) Pentium(R) 4 CPU 3.00GHz (2992.51-MHz 686-class CPU)
   Origin = "GenuineIntel"  Id = 0xf41  Stepping = 1
 
Features=0xbfebfbff<FPU,VME,DE,PSE,TSC,MSR,PAE,MCE,CX8,APIC,SEP,MTRR,PGE,MCA,CMOV,PAT,PSE36,CLFLUSH,DTS,ACPI,MMX,FXSR,SSE,SSE2,SS,HTT,TM,PBE>
   Features2=0x441d<SSE3,DTES64,MON,DS_CPL,CNXT-ID,xTPR>
   TSC: P-state invariant
real memory  = 2147483648 (2048 MB)
avail memory = 2075926528 (1979 MB)
ACPI APIC Table: <PTLTD          APIC  >
FreeBSD/SMP: Multiprocessor System Detected: 2 CPUs
FreeBSD/SMP: 1 package(s) x 1 core(s) x 2 HTT threads
  cpu0 (BSP): APIC ID:  0
  cpu1 (AP/HT): APIC ID:  1
...



I start now with a WITNESS build.

Btw, on which irc channel, (bsdcode, bsddev) could such an issue be 
discussed?

Thanks for any hint on how to track this down.

Andreas