Re: [GIT PULL] Please pull powerpc/linux.git powerpc-6.1-1 tag

[Guenter Roeck]

On 10/12/22 22:03, Nicholas Piggin wrote:
> On Thu Oct 13, 2022 at 10:21 AM AEST, Guenter Roeck wrote:
> > On Thu, Oct 13, 2022 at 11:03:34AM +1100, Michael Ellerman wrote:
> > > Guenter Roeck <linux@xxxxxxxxxxxx> writes:
> > > > On Wed, Oct 12, 2022 at 11:20:38AM -0600, Jason A. Donenfeld wrote:
> > > > > I've also managed to not hit this bug a few times. When it triggers,
> > > > > after "kprobes: kprobe jump-optimization is enabled. All kprobes are
> > > > > optimized if possible.", there's a long hang - tens seconds before it
> > > > > continues. When it doesn't trigger, there's no hang at that point in the
> > > > > boot process.
> > > >
> > > > I managed to bisect the problem. See below for results. Reverting the
> > > > offending patch fixes the problem for me.
> > >
> > > Thanks.
> > >
> > > This is probably down to me/us not testing with PREEMPT enabled enough.
> > Not sure. My configuration has
> >
> > CONFIG_PREEMPT_NONE=y
> > # CONFIG_PREEMPT_VOLUNTARY is not set
> > # CONFIG_PREEMPT is not set
>
> Thanks very much for helping with this. The config snippet you posted here
> https://lists.ozlabs.org/pipermail/linuxppc-dev/2022-October/249758.html
> has CONFIG_PREEMPT=y. How do you turn that into a .config, olddefconfig?
>
> I can't reproduce this so far using your config and qemu command line,
> but the patch you've bisected it to definitely could cause this. I'll
> keep trying...

Uuh, sorry, I think I got confused with running multiple bisects on the
same branch, and took the above from a different bisect run. You are
correct, PREEMPT is enabled in the configuration.

Timing is definitely involved; I see the problem more often on a loaded
system. To bisect it, I had to repeat the test for each bisect step
several times (I set the limit to 20 retries; that gave me reliable
results).

Guenter