Re: NMI hardlock stacktrace deadlock [was Re: Linux 5.2-rc5]

From: Josh Poimboeuf
Date: Mon Jun 24 2019 - 23:04:00 EST

On Wed, Jun 19, 2019 at 01:42:53PM -0700, Linus Torvalds wrote:
> On Wed, Jun 19, 2019 at 12:19 PM Chris Wilson <chris@xxxxxxxxxxxxxxxxxx> wrote:
> >
> > > Do you have the oops itself at all?
> >
> > An example at
> >
> >
> >
> > The bug causing the oops is clearly a driver problem. The rc5 fallout
> > just seems to be because of some shrinker changes affecting some object
> > reaping that were unfortunately still active. What perturbed the CI
> > team was the machine failed to panic & reboot.
> Hmm. It's hard to guess at the cause of that. The oopses themselves
> don't look like they are happening in any particularly bad context, so
> all the normal reboot-on-oops etc stuff _should_ work.

Looking at the dmesg, panic_on_oops doesn't seem to be enabled: it went
through the rewind_stack_do_exit() path instead of the panic() path. So
the system is apparently not configured to reboot on oops.

So I'd say the hang was presumably caused by a lock held by the oopsing
code. So it looks normal to me, other than the original oops.