!850 Fix race condition in __percpu_counter_sum() function within cpu hotplug

Merge Pull Request from: @henryze 
 
The dying CPU has been removed from the online_mask, but the hotplug notifier have not been called to fold the percpu count into the global counter sum.
This race condition is avoided by including the dying CPU in the iteration mask. 
 
Link:https://gitee.com/openeuler/kernel/pulls/850

 

Reviewed-by: Wei Li <liwei391@huawei.com>
Reviewed-by: Zheng Zengkai <zhengzengkai@huawei.com>
Signed-off-by: Zheng Zengkai <zhengzengkai@huawei.com>