/* * Common SMP CPU bringup/teardown functions */#include <linux/err.h>#include <linux/smp.h>#include <linux/init.h>#include <linux/sched.h>#include <linux/percpu.h> #include "smpboot.h" #ifdef CONFIG_GENERIC_SMP_IDLE_THREAD/* * For the hotplug case we keep the task structs around and reuse * them. */static DEFINE_PER_CPU(struct task_struct *, idle_threads); struct task_struct * __cpuinit idle_thread_get(unsigned int cpu){	struct task_struct *tsk = per_cpu(idle_threads, cpu); 	if (!tsk)		return ERR_PTR(-ENOMEM);	init_idle(tsk, cpu);	return tsk;} void __init idle_thread_set_boot_cpu(void){	per_cpu(idle_threads, smp_processor_id()) = current;} /** * idle_init - Initialize the idle thread for a cpu * @cpu:	The cpu for which the idle thread should be initialized * * Creates the thread if it does not exist. */static inline void idle_init(unsigned int cpu){	struct task_struct *tsk = per_cpu(idle_threads, cpu); 	if (!tsk) {		tsk = fork_idle(cpu);		if (IS_ERR(tsk))			pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);		else			per_cpu(idle_threads, cpu) = tsk;	}} /** * idle_threads_init - Initialize idle threads for all cpus */void __init idle_threads_init(void){	unsigned int cpu, boot_cpu; 	boot_cpu = smp_processor_id(); 	for_each_possible_cpu(cpu) {		if (cpu != boot_cpu)			idle_init(cpu);	}}#endif