Re: [Xen-devel] [stable-4.11] Heads-up: c719519 (x86/SMP: don't try to stop already stopped CPUs) causes 100% kexec/kdump failure

[Jan Beulich <jbeulich@xxxxxxxx>]

On 28.10.2019 18:30, Stonehouse, Robert wrote:
> Reverting one hunk via the following commit fixes things for me (this is an 
> experiment and not at all a proposed fix)
> ========
> --- a/xen/arch/x86/smp.c
> +++ b/xen/arch/x86/smp.c
> @@ -303,15 +303,15 @@ static void stop_this_cpu(void *dummy)
>  void smp_send_stop(void)
>  {
>      unsigned int cpu = smp_processor_id();
> +    
> +    local_irq_disable();
> +    fixup_irqs(cpumask_of(cpu), 0);
> +    local_irq_enable();
> 
>      if ( num_online_cpus() > 1 )
>      {
>          int timeout = 10;
>  
> -        local_irq_disable();
> -        fixup_irqs(cpumask_of(cpu), 0);
> -        local_irq_enable();

Are you saying we get here the first time only when num_online_cpus()
already returns 1 (but there are actually multiple CPUs, i.e. affinity
changes are actually needed)? If so - why?

Jan

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