Re: [rcu] 2f08469563: BUG:kernel_reboot-without-warning_in_boot_stage

[Nick Desaulniers]

On Tue, May 19, 2020 at 11:32 AM Marco Elver <elver@xxxxxxxxxx> wrote:
>
> This fixes the problem:
> https://lkml.kernel.org/r/20200519182459.87166-1-elver@xxxxxxxxxx
>
> I suppose there are several things that happened that caused the above
> bisected changes to trigger this. Hard to say how exactly the above
> bisected changes caused this to manifest, because during early boot
> (while uninitialized) KASAN may just randomly enter kasan_report()
> before the branch (annotated with likely(), which is caught by the
> branch tracer) prevents it from actually generating a report. However,
> if it goes branch tracer -> KASAN -> branch tracers -> KASAN ..., then
> we crash. If I had to guess some combination of different code gen,
> different stack and/or data usage. So all the above bisected changes
> (AFAIK) were red herrings. :-)

Thanks for chasing to resolution.  Consider using a variable to store
a list of flags, as that code (before your patch) invokes the compiler
multiple times to answer the same question.
-- 
Thanks,
~Nick Desaulniers