Re: [Xen-devel] [PATCH RFC 01/49] xen/sched: call cpu_disable_scheduler() via cpu notifier

[Julien Grall <julien.grall@xxxxxxx>]

Hi,

On 3/29/19 3:08 PM, Juergen Gross wrote:
> cpu_disable_scheduler() is being called from __cpu_disable() today.
> There is no need to execute it on the cpu just being disabled, so use
> the CPU_DEAD case of the cpu notifier chain. Moving the call out of
> stop_machine() context is fine, as we just need to hold the domain RCU
> lock and need the scheduler percpu data to be still allocated.
>
> Add another hook for CPU_DOWN_PREPARE to bail out early in case
> cpu_disable_scheduler() would fail. This will avoid crashes in rare
> cases for cpu hotplug or suspend.
>
> While at it remove a superfluous smp_mb() in the ARM __cpu_disable()
> incarnation.
This is not obvious why the smp_mb() is superfluous. Can you please 
provide more details on why this is not necessary?
Cheers,

--
Julien Grall

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