Re: What does 'lock order reversal' mean?

Jon Noack <noackjr_at_alumni.rice.edu> wrote:
> On 4/9/2004 5:04 AM, Artem Koutchine wrote:
> > When i run test perl scripts (6 processes in parallel)
> > which crate a big array, manupulate it, free and over again
> > so 2GB of ram is used up and system starts using swap i see 
> > the message below (only onces). What does it mean?
> > 
> > Apr  7 20:16:34 new kernel: lock order reversal
> > Apr  7 20:16:34 new kernel: 1st 0xc79446b4 vm object (vm object) _at_
> > /usr/src/sys/vm/swap_pager.c:1313
> > Apr  7 20:16:35 new kernel: 2nd 0xc08b9e00 swap_pager swhash (swap_pager
> > swhash) _at_ /usr/src/sys/vm/swap_pager.c:1803
> > Apr  7 20:16:35 new kernel: 3rd 0xc7898294 vm object (vm object) _at_
> > /usr/src/sys/vm/uma_core.c:886
> 
> This is:
> 1) A FAQ.
> 2) A false positive.
> 3) Completely harmless.
> 
> Previously reported to the list:
> 1) 04/07/2004 (by you)
> 2) 03/31/2004
> 3) 03/28/2004
> 4) 03/24/2004
> 5) 03/22/2004
> 6) 03/18/2004
> 7) ...
> 
> For a good explanation of lock order reversals:
> http://lists.freebsd.org/pipermail/freebsd-current/2003-December/016617.html
> 
> I'll put up a webpage of false-positives if someone will commit a change 
> in the LOR warning to point to it (or something similar to this):
> "lock order reversal: please see http://example.com for status before 
> reporting"
> 
> I still think it would be best if this page were on the FreeBSD website, 
> but I'll host it if necessary.

Let's make it happen.  If either you want to host it or have me put it in 
http://people.freebsd.org/~green/ for now, that will be easiest.  Actually 
putting it somewhere in the whole "FreeBSD web site" infrastructure means 
finding someone from the doc committers who knows more about it than I would.

It would be better just to have a bug database that could handle this sort 
of task, maybe one day....

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