Messages in this thread | | | Date | Wed, 12 Oct 2022 22:20:01 -0700 | From | Guenter Roeck <> | Subject | Re: [GIT PULL] Please pull powerpc/linux.git powerpc-6.1-1 tag |
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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@roeck-us.net> 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
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