Note that switching branches results in some locks being taken,
particularly the CPU hotplug lock (in order to avoid races against
-CPUs being brought in the kernel whilst the kernel is getting
+CPUs being brought in the kernel while the kernel is getting
patched). Calling the static key API from within a hotplug notifier is
thus a sure deadlock recipe. In order to still allow use of the
functionnality, the following functions are provided: