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

Chen Gong
2011-09-29T03:14:11Z

于 2011/9/24 14:10, canquan.shen 写道:
> 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@huawei.com>
> ---
> 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);

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