kernel crash

[Paul Goyette <paul%whooppee.com@localhost>]

It's been a long time since I've had a kernel crash on my production system, 
but today I've had four!

Twice the system just hangs, but the other two times I got an attempted crash 
dump.  Unfortunately it would appear that sparse_dumps might not be working 
100% on amd64, since I got this when trying to examine the core dump:

(gdb) target kvm /var/crash/netbsd.1.core
#0  0xffffffff8021d91e in cpu_reboot (howto=260, bootstr=<optimized out>)
     at /build/netbsd-local/src/sys/arch/amd64/amd64/machdep.c:779
warning: Source file is more recent than executable.
779                     sparse_dump_physmap = (void *)uvm_km_alloc(kernel_map,
(gdb) bt
#0  0xffffffff8021d91e in cpu_reboot (howto=260, bootstr=<optimized out>)
     at /build/netbsd-local/src/sys/arch/amd64/amd64/machdep.c:779
#1  0xffffffff802ce686 in vpanic (
     fmt=0xffffffff806cf7f0 "blkfree: freeing free block",
     ap=0xfffffe813ce6f480) at /build/netbsd-local/src/sys/kern/subr_prf.c:284
#2  0xffffffff802ce73a in panic (fmt=<unavailable>)
     at /build/netbsd-local/src/sys/kern/subr_prf.c:200
#3  0xffffffff806b76c4 in ?? ()
#4  0xfffffe876e9780f8 in ?? ()

(I could turn off sparse dumps, but it would take a very long time for the 
system to dump 32GB, and even longer for savecore to copy it after reboot.)

All four of the crashes have happened while trying to back up my /homes 
directory using dump(8).  /homes has WAPBL turned on, howver I have used 'fsck 
-f' to veriy that the file system is clean.  I have also verified that the 
destination file system is clean.  (It is a 1TB partition on a 2TB removable 
USB drive.)

Here is the dump command I'm using:

        dump -0au -h 0 -X -f- /home | gzip -9 > ${1}/home.dmp.gz

Anyone have a clue on how to proceed?


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