tick_nohz_cpu_hotpluggable
&& tick_nohz_cpu_hotpluggable(cpu);
extern bool tick_nohz_cpu_hotpluggable(unsigned int cpu);
return tick_nohz_cpu_hotpluggable(cpu) ? 0 : -EBUSY;
if (!tick_nohz_cpu_hotpluggable(cpu)) {