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Date:   Sat, 17 Aug 2019 22:21:48 +0200 (CEST)
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Guenter Roeck <linux@roeck-us.net>
cc:     Peter Zijlstra <peterz@infradead.org>, x86@kernel.org,
        Ingo Molnar <mingo@redhat.com>, linux-kernel@vger.kernel.org,
        Borislav Petkov <bp@alien8.de>
Subject: Re: sched: Unexpected reschedule of offline CPU#2!
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On Fri, 16 Aug 2019, Guenter Roeck wrote:
> On Fri, Aug 16, 2019 at 12:22:22PM +0200, Thomas Gleixner wrote:
> > diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
> > index 75fea0d48c0e..625627b1457c 100644
> > --- a/arch/x86/kernel/process.c
> > +++ b/arch/x86/kernel/process.c
> > @@ -601,6 +601,7 @@ void stop_this_cpu(void *dummy)
> >  	/*
> >  	 * Remove this CPU:
> >  	 */
> > +	set_cpu_active(smp_processor_id(), false);
> >  	set_cpu_online(smp_processor_id(), false);
> >  	disable_local_APIC();
> >  	mcheck_cpu_clear(this_cpu_ptr(&cpu_info));
> > 
> No luck. The problem is still seen with this patch applied on top of
> the mainline kernel (commit a69e90512d9def6).

Yeah, was a bit too naive ....

We actually need to do the full cpuhotplug dance for a regular reboot. In
the panic case, there is nothing we can do about. I'll have a look tomorrow.

Thanks,

	tglx