On Mon, 19 Oct 2015, Boris Ostrovsky wrote:
> On 10/19/2015 12:55 PM, Stefano Stabellini wrote:
> > When offlining a cpu, instead of cpu_down, call device_offline, which
> > also takes care of updating the cpu.dev.offline field. This keeps the
> > sysfs file /sys/devices/system/cpu/cpuN/online, up to date. Also move
> > the call to disable_hotplug_cpu, because it makes more sense to have it
> > there.
> >
> > Signed-off-by: Stefano Stabellini <stefano.stabell...@eu.citrix.com>
> > CC: konrad.w...@oracle.com
> > CC: boris.ostrov...@oracle.com
> > CC: david.vra...@citrix.com
> > ---
> > drivers/xen/cpu_hotplug.c | 3 ++-
> > 1 file changed, 2 insertions(+), 1 deletion(-)
> >
> > diff --git a/drivers/xen/cpu_hotplug.c b/drivers/xen/cpu_hotplug.c
> > index 43de1f5..78804b5 100644
> > --- a/drivers/xen/cpu_hotplug.c
> > +++ b/drivers/xen/cpu_hotplug.c
> > @@ -18,6 +18,8 @@ static void enable_hotplug_cpu(int cpu)
> > static void disable_hotplug_cpu(int cpu)
> > {
> > + if (cpu_online(cpu))
> > + device_offline(get_cpu_device(cpu));
> > if (cpu_present(cpu))
> > xen_arch_unregister_cpu(cpu);
>
> Do we want to call device_online() when plugging cpu in?
I don't know: that would automatically bring the cpu online after the
user hot-plugs it. Is it what we want? Current one would have to manually:
echo 1 > /sys/devices/system/cpu/cpu1/online
I thought that was the expected behaviour?
> And take sysfs lock?
I think you are right: we need to protect the device_offline (and
device_online if we add it) with lock_device_hotplug and
unlock_device_hotplug. Thanks!
> > @@ -55,7 +57,6 @@ static void vcpu_hotplug(unsigned int cpu)
> > enable_hotplug_cpu(cpu);
> > break;
> > case 0:
> > - (void)cpu_down(cpu);
> > disable_hotplug_cpu(cpu);
> > break;
> > default:
>
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