Re: LOR (swap_pager.c , uma_core.c)

Kris Kennaway <kris_at_obsecurity.org> wrote:
> On Thu, Dec 04, 2003 at 05:30:30PM +0100, Andy Hilker wrote:
> > 
> > Hi,
> > 
> > one of my servers with SMP crashs every few minutes oder a few hours
> > under heavy load (e.g. /usr/ports/math/mprime, mprime -t )
> > With SMP disabled, server runs very stable.
> > 
> > kernel: lock order reversal   
> > kernel: 1st 0xc2113c60 vm object (vm object) _at_ /usr/src/sys/vm/swap_pager.c:1323
> > kernel: 2nd 0xc076ef40 swap_pager swhash (swap_pager swhash) _at_ /usr/src/sys/vm/swap_pager.c:1838
> > kernel: 3rd 0xc1037b58 vm object (vm object) _at_ /usr/src/sys/vm/uma_core.c:881
> > kernel: Stack backtrace:
> 
> This is a known false positive, reported at least once a day.  Remove
> WITNESS_DDB from your kernel, or at least remove DDB_UNATTENDED so
> your system won't reboot when these harmless WITNESS warnings show up.

Here's all of the sysctls you should know about:

debug.trace_on_panic
debug.debugger_on_panic
kern.sync_on_panic
machdep.ddb_on_nmi
debug.witness_watch
debug.witness_ddb
debug.witness_trace
debug.witness_skipspin

If you want to change debug.witness_skipspin, though, that has to be set as 
a tunable in /boot/loader.conf instead of /etc/sysctl.conf.

If you're actually running into real crashes, there's a possibility that 
this might help:
	http://www.FreeBSD.org/~jhb/patches/turnstile.patch

-- 
Brian Fundakowski Feldman                           \'[ FreeBSD ]''''''''''\
  <> green_at_FreeBSD.org                               \  The Power to Serve! \
 Opinions expressed are my own.                       \,,,,,,,,,,,,,,,,,,,,,,\