Subject: Re: [PATCH] powerpc/smp: Wait until secondaries are active & online

From: Stewart Smith <[email-masked]>
Date: Thu, 26 Feb 2015 08:51:10 +1100

Michael Ellerman <[email-masked]> writes:
> Anton has a busy ppc64le KVM box where guests sometimes hit the infamous
> "kernel BUG at kernel/smpboot.c:134!" issue during boot:
>
>   BUG_ON(td->cpu != smp_processor_id());
>
> Basically a per CPU hotplug thread scheduled on the wrong CPU. The oops
> output confirms it:
>
>   CPU: 0
>   Comm: watchdog/130

Has anyone seen this on powernv before?

I seem to be able to very reliably get such crashes with my
(experimental) gcov enabled skiboot on P7 (and P8, but I've had more
time on P7 than P8).

Hoping to try the patch later today.