Re: [PATCH 0/2 v3] cpu hotplug: Preserve topology directory after soft remove event
From: Peter Zijlstra
Date: Mon Sep 26 2016 - 07:59:59 EST
On Mon, Sep 26, 2016 at 07:45:37AM -0400, Prarit Bhargava wrote:
> > But then code which reads those will have to *know* that those cores are
> > offline - otherwise it would be confused by what it is reading there.
> When offline, /sys/devices/system/cpuX/cpu/online is 0. The problem is that
> when online is 0, topology disappears so there is no way to determine _the
> location_ of the offline'd thread.
As far as all that code is concerned, that CPU doesn't even have a
While there might be some distinction between hotplug and physical
hotplug on the user API side (I really wouldn't know), there isn't on
the kernel side.
Once you unplug a CPU, its _gone_. There isn't another hotplug operation
once you really take the CPU out.
Offline means out gone, vamoosh.
And it doesn't make sense to talk about the location of a resource
that's not there.