Re: sysctl -a causes kernel trap 12

On Thu, Jan 10, 2013 at 4:25 PM, Xin Li <delphij_at_delphij.net> wrote:

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> To all: this became more and more hard to replicate lately.  I've
> tried these options and the most important progress is that it's
> possible to get a crashdump when debug.debugger_on_panic=0 and I
> managed to get a backtrace which indicates the panic occur when trying
> to do mtx_lock(&Giant) -> __mtx_lock_sleep -> turnstile_wait ->
> propagate_priority, but after I've added some instruments to the
> surrounding code and enabled INVARIANT and/or WITNESS, it mysteriously
> went away.
>
> Reverting my instruments code and update to latest svn makes the issue
> disappear for one day.  I've hit it again today but unfortunately
> didn't get a successful dump and after reboot I can't reproduce it
> again :(
>
> Still trying...
>

Any updates Xin?

I was actually hitting what I believe to be exactly the same issue as you
on one of my systems, and, as you've seen, adding any extra debugging or
diagnostics seemed to eliminate the issue.

I was able to generate quite a few vmcores and still have these sitting
around in my filesystem (along with the kernels that helped produce them).

I can recreate this crash on my system by compiling the NVIDIA driver with
clang at -01 and above. Although it's been noted that this issue has been
seen in scenarios without an NIVIDIA driver in the mix, whatever is
happening in the kernel to cause the panic is somehow triggered by this, at
least on my system.

-Brandon