consistent crashes on NetBSD 7.99.24 amd64 built 19th Dec 15

[Dave Tyson <dtyson%anduin.org.uk@localhost>]

I seem be able to trigger a consistent crash on a recent install by doing 
heavy disk I/O like deleting a lot of files.

System is an Intel quad-core running :

NetBSD cruncher.anduin.org.uk 7.99.24 NetBSD 7.99.24 (GENERIC) #1: Sat Dec 19 
11:15:14 GMT 2015  
root%cruncher.anduin.org.uk@localhost:/usr/obj/sys/arch/amd64/compile/GENERIC amd64

Having built about 500 packages I decided after a couple of weeks to clear the 
work files out by:

cd /usr/pkgsrc
rm -rf */*/work

This triggers a panic - sometimes I get a core dump, but other times the 
machine fails to dump core and just reboots.

panic: kernel diagnostic assertion "vp->v_usecount != 0" failed: file 
"/usr/src/sys/kern/vfs_vnode.c", line 822 
cpu3: Begin traceback...
vpanic() at netbsd:vpanic+0x13c
kern_assert() at netbsd:kern_assert+0x4f
vref() at netbsd:vref+0x74
getcwd_common() at netbsd:getcwd_common+0x69
procfs_dir.constprop.0() at netbsd:procfs_dir.constprop.0+0xca
procfs_getattr() at netbsd:procfs_getattr+0x487
VOP_GETATTR() at netbsd:VOP_GETATTR+0x34
vn_stat() at netbsd:vn_stat+0x36
do_sys_statat() at netbsd:do_sys_statat+0x96
sys___lstat50() at netbsd:sys___lstat50+0x25
syscall() at netbsd:syscall+0x9c
--- syscall (number 441) ---
7f7ff3ea99ca:
cpu3: End traceback...
uvm_fault(0xfffffe83e5561a20, 0x0, 2) -> e
fatal page fault in supervisor mode
trap type 6 code 
2 rip ffffffff807e901b cs 8 rflags 10286 cr2 84 ilevel 8 rsp fffffe811e765e00
dumping to dev 0,1 (offset=217511, size=4167225):
curlwp 0xfffffe83db0b9940 pid 954.17 lowest kstack 0xfffffe811e7622c0

No core dump from that one, but after a reload repeating the same commands to 
clear out the remainder resulted in:

panic: kernel diagnostic assertion "vp->v_usecount != 0" failed: file 
"/usr/src/sys/kern/vfs_vnode.c", line 822 
cpu1: Begin traceback...
vpanic() at netbsd:vpanic+0x13c
kern_assert() at netbsd:kern_assert+0x4f
vref() at netbsd:vref+0x74
getcwd_common() at netbsd:getcwd_common+0x69
procfs_dir.constprop.0() at netbsd:procfs_dir.constprop.0+0xca
procfs_getattr() at netbsd:procfs_getattr+0x487
VOP_GETATTR() at netbsd:VOP_GETATTR+0x34
vn_stat() at netbsd:vn_stat+0x36
do_sys_statat() at netbsd:do_sys_statat+0x96
sys___lstat50() at netbsd:sys___lstat50+0x25
syscall() at netbsd:syscall+0x9c
--- syscall (number 441) ---
7f7ff3ea99ca:
cpu1: End traceback...
uvm_fault(0xfffffe83f350da18, 0x0, 2) -> e
ufvatma_faull t
p(ag0e xfafulftf fifne s8u4p1earvfis4ofre 6mode,
 0x0, 2) -> e
dumping to dev 0,1 (offset=217511, size=4167225):
trap type 6 code 2 rip ffffffff807e901b cs 8 rflags 10286 cr2 84 ilevel 8 rsp 
ffatfaflffaeg8e1 f1auelt0 1inc es0up0e
rvisor mode
dump curlwp 0xfffffe83f1718860 pid 1062.9 lowest kstack 0xfffffe81t1rea0p1 
9t2ycp0e
 6 code 2 rip ffffffff807e901b cs 8 rflags 10286 cr2 84 ilevel 8 rsp 
fffffe811ded4e00
curlwp 0xfffffe8418a790a0 pid 96.2 lowest kstack 0xfffffe811ded12c0

Have a core dump for this, but there is obviously some corruption.
I can make the core dump/symbols available. Worth a pr?

Dave

-- 
=========================================
Phone: 07805784357
Open Source O/S: www.netbsd.org
Caving: http://www.wirralcavinggroup.org.uk
=========================================