9.2-RC4 amd64 panic: vm_page_unwire

[John Marshall]

I'm running 9.2-RC4 on a handful of desktop and server machines (both
i386 and amd64).  I have seen three panics (all vm_page_unwire) on one
of those systems only (amd64 server) during the past week.

The first two panics were triggered when shutting down the ntpd daemon
(a recent development snapshot version of ntpd: 4.2.7p387).  Exiting a
later release (p388) has not triggered the panic.  The system panicked
again overnight, this time while acting as an sftp server receiving
large (GB) files from another system.

Fri Sep 20 16:48:34 2013 +1000
  ozsrv04# kgdb kernel.debug /var/crash/vmcore.0
  ...
  panic: vm_page_unwire: page 0xfffffe0233510578's wire count is zero
  cpuid = 3
  KDB: stack backtrace:
  #0 0xffffffff80490268 at kdb_backtrace+0x68
  #1 0xffffffff8045630a at panic+0x21a
  #2 0xffffffff8068bbc2 at vm_page_unwire+0x102
  #3 0xffffffff80678702 at vm_fault_unwire+0xd2
  #4 0xffffffff80680841 at vm_map_delete+0x171
  #5 0xffffffff80680abf at vm_map_remove+0x5f
  #6 0xffffffff80683ee9 at vmspace_exit+0xc9
  #7 0xffffffff8041f3ad at exit1+0x72d
  #8 0xffffffff804203ae at sys_sys_exit+0xe
  #9 0xffffffff806afd6f at amd64_syscall+0x3bf
  #10 0xffffffff8069a817 at Xfast_syscall+0xf7
  Uptime: 2d0h35m3s
 
Fri Sep 20 17:49:57 2013 +1000
  ozsrv04# kgdb kernel.debug /var/crash/vmcore.1
  ...
  panic: vm_page_unwire: page 0xfffffe022f5fc238's wire count is zero
  cpuid = 2
  KDB: stack backtrace:
  #0 0xffffffff80490268 at kdb_backtrace+0x68
  #1 0xffffffff8045630a at panic+0x21a
  #2 0xffffffff8068bbc2 at vm_page_unwire+0x102
  #3 0xffffffff80678702 at vm_fault_unwire+0xd2
  #4 0xffffffff80680841 at vm_map_delete+0x171
  #5 0xffffffff80680abf at vm_map_remove+0x5f
  #6 0xffffffff80683ee9 at vmspace_exit+0xc9
  #7 0xffffffff8041f3ad at exit1+0x72d
  #8 0xffffffff804203ae at sys_sys_exit+0xe
  #9 0xffffffff806afd6f at amd64_syscall+0x3bf
  #10 0xffffffff8069a817 at Xfast_syscall+0xf7
  Uptime: 59m51s

Fri Sep 27 01:51:44 2013 +1000
  ozsrv04# kgdb kernel.debug /var/crash/vmcore.2
  ...
  panic: vm_page_unwire: page 0xfffffe0239ecfc48's wire count is zero
  cpuid = 5
  KDB: stack backtrace:
  #0 0xffffffff80490268 at kdb_backtrace+0x68
  #1 0xffffffff8045630a at panic+0x21a
  #2 0xffffffff8068bbc2 at vm_page_unwire+0x102
  #3 0xffffffff804d857e at vfs_vmio_release+0x10e
  #4 0xffffffff804dadc8 at getnewbuf+0x468
  #5 0xffffffff804dbb2f at getblk+0x5df
  #6 0xffffffff80632bb1 at ffs_balloc_ufs2+0x15c1
  #7 0xffffffff8065a8d6 at ffs_write+0x246
  #8 0xffffffff8070a18f at VOP_WRITE_APV+0x11f
  #9 0xffffffff80505e77 at vn_write+0x1f7
  #10 0xffffffff80503b51 at vn_io_fault+0xb1
  #11 0xffffffff804a387c at dofilewrite+0x9c
  #12 0xffffffff804a3b54 at kern_writev+0x54
  #13 0xffffffff804a3bf5 at sys_write+0x65
  #14 0xffffffff806afd6f at amd64_syscall+0x3bf
  #15 0xffffffff8069a817 at Xfast_syscall+0xf7
  Uptime: 6d7h46m14s

Is this a known problem?  Should I file a PR?  What additional
information should I provide?

I have made the core.txt.[0-2] files available in the following
directory.  The directory is not browsable.

  http://www.riverwillow.net.au/~john/92rc4/

-- 
John Marshall
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