9.2-RC4 amd64 panic: vm_page_unwire

[John Marshall]

On Mon, 30 Sep 2013, 19:55 +1000, John Marshall wrote:
> > >> > On Fri, 27 Sep 2013, 11:12 +0300, Konstantin Belousov wrote:
> > >> >> On Fri, Sep 27, 2013 at 10:07:28AM +1000, John Marshall wrote:
> > >> >> > 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/
> > >> >>
> > >> >> This might be fixed by r254087-r254090 on stable/9.

As well as applying those patches to releng/9.2, and still seeing the
panic, I have upgraded one of the systems to stable/9 and still see the
panic.

> Another data point: both systems on which I have seen this panic have
> the ipmi driver compiled in.  ipmi makes the BMC's watchdog timer
> available to the system.

I ruled this out.  I recompiled a kernel with no ipmi driver (so that
removes the watchdog timer too) but the system would still panic on
shutdown when stopping ntpd.

I have also reverted to the STABLE ntpd distribution (4.6.4p5
2011-12-24) and still see the panic.

I took one of the systems back to releng/9.1 (9.1-RELEASE-p7).  Its
kernel includes the ipmi driver, I am running watchdogd, I am running
ntpd, I have rebooted several times and have never seen a panic.

So, I now have one system on 9.1-RELEASE (panic-free); and the second
system on 9-STABLE (panics).  Previously I had both systems on
9.2-RELEASE and panicking.

Another common factor with all but one of the panics I have seen is that
the process which appears to trigger the panic is a 'realtime' process.

rwsrv08# top -b 200 | awk '(/^  PID/ || $5~/^r/)'
  PID USERNAME    THR PRI NICE   SIZE    RES STATE   C   TIME   WCPU COMMAND
 1739 root          1 -52   r0 12056K  8040K nanslp  7   0:02  0.00% watchdogd
 1911 root          1 -52  r0F 32668K 18468K select  7   0:02  0.00% ntpd

Here is a recent stable/9 tripping over watchdogd on shutdown:

FreeBSD 9.2-STABLE #0 r256029:
  .
  Stopping watchdogd.
  Waiting for PIDS: 1729
  panic: vm_page_unwire: page 0xfffffe042bdae2d8's wire count is zero
  cpuid = 1
  KDB: stack backtrace:
  #0 0xffffffff804e8188 at kdb_backtrace+0x68
  #1 0xffffffff804adcba at panic+0x21a
  #2 0xffffffff80718dd2 at vm_page_unwire+0x102
  #3 0xffffffff80705a52 at vm_fault_unwire+0xd2
  #4 0xffffffff8070db41 at vm_map_delete+0x171
  #5 0xffffffff8070ddbf at vm_map_remove+0x5f
  #6 0xffffffff80711199 at vmspace_exit+0xc9
  #7 0xffffffff804773dd at exit1+0x72d
  #8 0xffffffff804783de at sys_sys_exit+0xe
  #9 0xffffffff8073e86f at amd64_syscall+0x3bf
  #10 0xffffffff80729307 at Xfast_syscall+0xf7

-- 
John Marshall
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