kern/39152: Reader / writer lock error: rw_vector_exit: assertion failed: RW_COUNT(rw) != 0

[bsd-xen%roguewrt.org@localhost]

>Number:         39152
>Category:       kern
>Synopsis:       panic on pwd within non-existent directory
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    kern-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Tue Jul 15 23:30:00 +0000 2008
>Originator:     bsd-xen%roguewrt.org@localhost
>Release:        NetBSD 4.99.69
>Organization:
        
>Environment:
        
        
System: NetBSD symbiote.internal 4.99.69 NetBSD 4.99.69 (XEN3_DOMU) #0: Sun Jul 
13 23:07:37 EST 2008 
root%spike.internal@localhost:/usr/obj/sys/arch/amd64/compile/XEN3_DOMU amd64
Architecture: x86_64
Machine: amd64
>Description:

When on an NFS client and within an NFS mount/randomdir, removing randomdir on
the server and issuing a pwd on the client within the non-existent directory
causes the following panic:

panic: lock error
fatal breakpoint trap in supervisor mode
trap type 1 code 0 rip ffffffff80364ab5 cs e030 rflags 246 cr2  7f7ffda11ed0 
cpl 0 rsp ffffa0002535f7e0
Stopped in pid 4734.1 (ksh) at  netbsd:breakpoint+0x5:  leave
breakpoint() at netbsd:breakpoint+0x5
panic() at netbsd:panic+0x255
lockdebug_abort() at netbsd:lockdebug_abort+0x42
rw_vector_exit() at netbsd:rw_vector_exit+0xa6
vlockmgr() at netbsd:vlockmgr+0xd8
VOP_UNLOCK() at netbsd:VOP_UNLOCK+0x28
vput() at netbsd:vput+0x1d
getcwd_common() at netbsd:getcwd_common+0x30f
sys___getcwd() at netbsd:sys___getcwd+0xc3
syscall() at netbsd:syscall+0x98
ds          0xf7f0
es          0xe02b
fs          0xf7a0
gs          0x207
rdi         0
rsi         0xd
rbp         0xffffa0002535f7e0
rbx         0xffffa0002535f7f0
rdx         0
rcx         0
rax         0x1
r8          0xffffffff80577f80  cpu_info_primary
r9          0x1
r10         0xffffa0002535f700
r11         0xffffffff8037c460  xenconscn_putc
r12         0x100
r13         0xffffffff803ed4e1  copyright+0xd281
r14         0xffffffff80574000  rwlock_lockops
r15         0xffffa00001403400
rip         0xffffffff80364ab5  breakpoint+0x5
cs          0xe030
rflags      0x246
rsp         0xffffa0002535f7e0
ss          0xe02b
netbsd:breakpoint+0x5:  leave


>How-To-Repeat:

As described above, ensure an NFS client shell is within a directory within
an NFS mount, removed that directory on the server and issue a pwd on the
client.

>Fix:
        

>Unformatted: