Re: [PATCH v5] acpi: Fix CPU hot removal problem

[canquan.shen]

On 2011/9/29 11:14, Chen Gong wrote:
> ä 2011/9/24 14:10, canquan.shen åé:
> > We run linux as a guest in Xen environment. When we used the xen tools
> > (xm vcpu-set <n>) to hot add and remove vcpu to and from the guest, we
> > encountered the failure on vcpu removal. We found the reason is that it
> > did't go to really remove cpu in the cpu removal code path.
> >
> > This patch adds acpi_bus_hot_remove_device in
> > acpi_process_hotplug_notify to
> > fix this issue. With this patch, it works fine for us.
> >
> > Signed-off-by: Canquan Shen <shencanquan@xxxxxxxxxx>
> > ---
> > drivers/acpi/processor_driver.c | 13 +------------
> > drivers/acpi/scan.c | 4 ++--
> > include/acpi/acpi_bus.h | 1 +
> > 3 files changed, 4 insertions(+), 14 deletions(-)
> >
> > diff --git a/drivers/acpi/processor_driver.c
> > b/drivers/acpi/processor_driver.c
> > index a4e0f1b..8429688 100644
> > --- a/drivers/acpi/processor_driver.c
> > +++ b/drivers/acpi/processor_driver.c
> > @@ -665,18 +665,7 @@ static void
> > acpi_processor_hotplug_notify(acpi_handle handle,
> > case ACPI_NOTIFY_EJECT_REQUEST:
> > ACPI_DEBUG_PRINT((ACPI_DB_INFO,
> > "received ACPI_NOTIFY_EJECT_REQUEST\n"));
> > -
> > - if (acpi_bus_get_device(handle, &device)) {
> > - printk(KERN_ERR PREFIX
> > - "Device don't exist, dropping EJECT\n");
> > - break;
> > - }
> > - pr = acpi_driver_data(device);
> > - if (!pr) {
> > - printk(KERN_ERR PREFIX
> > - "Driver data is NULL, dropping EJECT\n");
> > - return;
> > - }
> > + acpi_bus_hot_remove_device(handle);
>
> As the description in __acpi_os_execute(in acpi_os_hotplug_execute),
> /*
> * We can't run hotplug code in keventd_wq/kacpid_wq/kacpid_notify_wq
> * because the hotplug code may call driver .remove() functions,
> * which invoke flush_scheduled_work/acpi_os_wait_events_complete
> * to flush these workqueues.
> */
> If so, why not using following call:
>
> acpi_os_hotplug_execute(acpi_bus_hot_remove_device, acpi_device->handle);

It is ok if using the acpi_os_hotplug_execute. but it is complex and 
more time for removal cpu because it is add to queue and some time the 
work will be called.
I think that it is clear to call directly acpi_bus_hot_remove_device 
function in acpi_processor_hotplug_notify.


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