panic: assertion: error == 0 in hammer_start_transaction

[Rumko <rumcic@xxxxxxxxx>]

The machine was mostly idle and the panic happened during the night when I was
sleeping, so I don't remember much what I was running.
The only thing I do remember, was a vkernel running under gdb (still have to
find out why when running a diskless vkernel outside gdb it displays quite a
few "RPC timeout for server 192.168.0.16" before the network starts working
and goes on booting, but if I run the vkernel under gdb, I only get perhaps 2
of those messages and after that nothing happens - gets stuck) which was
semi-diskless (root on nfs, and one hammer fs partition on the first vkd, but
since it was stuck at the RPC timeout messages it shouldn't have gotten far
enough to mount the root, let alone the local hammer partition - unless it
started booting sometime during the night).

The backtrace:
panic: assertion: error == 0 in hammer_start_transaction
mp_lock = 00000000; cpuid = 0
Trace beginning at frame 0xe28c9968
panic(e28c998c,c02c6806,e28c9a84,c39a6738,e28c99a8) at panic+0x14d
panic(c03d0698,c03de4df,c03bbd41,6,45d61) at panic+0x14d
hammer_start_transaction(e28c9a84,debc0000,c39a6738,1,1) at
hammer_start_transaction+0x41
hammer_ioctl(de0bc550,c02c6806,e28c9c1c,1,c39a6738) at hammer_ioctl+0x2d
hammer_vop_ioctl(e28c9ae0,c04314e0,d272ad10,e27c46e8,0) at
hammer_vop_ioctl+0x2f
vop_ioctl(d272ad10,e27c46e8,c02c6806,e28c9c1c,1) at vop_ioctl+0x38
vn_ioctl(d61e90c0,c02c6806,e28c9c1c,c39a6738,d61e90c0) at vn_ioctl+0xbf
mapped_ioctl(4,c02c6806,bfbff8e0,0,e28c9d34) at mapped_ioctl+0x3e1
sys_ioctl(e28c9cf0,6,1e82,0,d8f675d8) at sys_ioctl+0x16
syscall2(e28c9d40) at syscall2+0x265
Xint0x80_syscall() at Xint0x80_syscall+0x36
boot() called on cpu#0

The dump is located at leaf:~rumko/crash/{kernel,vmcore}.0

The kernel was compiled on the 2nd January around noon CET ... so the sources
should have been from around then as well.
-- 
Regards,
Rumko