On Wed, Jul 31, 2019 at 04:20:12PM +0000, Visa Hankala wrote:
> On Wed, Jul 31, 2019 at 05:46:08PM +0200, Raimo Niskanen wrote:
> > I have enabled Witness, it went so-so. We'll see what it catches.
> >
> > I downloaded 6.5 amd64 src.tar.gz and sys.tar.gz, unpacked them,
> > applied all patches for stable 001-006 and built a kernel with:
> > include "arch/amd64/conf/GENERIC"
> > option MULTIPROCESSOR
> > option MP_LOCKDEBUG
> > option WITNESS
> >
> > Then I activated in /etc/sysctl.conf:
> > ddb.console=1
> > kern.witness.locktrace=1
> > kern.witness.watch=3
> >
> > For fun, I pressed Ctrl+Alt+Esc at the console, got a ddb> prompt and typed
> > "show witness". It printed lots of info, I scrolled down to the end, but
> > during the printout there was an UVM fault:
> >
> > Spin locks:
> > /usr/src/sys/....
> > :
> > bla bla bla
> > :
> > uvm_fault(0xffffffff81e03b50, 0xffff800022368360, 0, 1) -> e
> > kernel: page fault trap, code=0
> > Faulted in DDB: continuing...
>
> The output of "show witness" is unlikely to be useful in your case.
> It is more of a tool for debugging witness. You can ignore it.
> However, "show all locks" might display interesting information
> after a witness-related panic.
Ok, great!
It is just that an uvm_fault during show witness felt like a bad thing...
--
/ Raimo Niskanen, Erlang/OTP, Ericsson AB
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