1 /* 2 * Common SMP CPU bringup/teardown functions 3 */ 4 #include <linux/err.h> 5 #include <linux/smp.h> 6 #include <linux/init.h> 7 #include <linux/sched.h> 8 #include <linux/percpu.h> 9 10 #include "smpboot.h" 11 12 #ifdef CONFIG_GENERIC_SMP_IDLE_THREAD 13 /* 14 * For the hotplug case we keep the task structs around and reuse 15 * them. 16 */ 17 static DEFINE_PER_CPU(struct task_struct *, idle_threads); 18 19 struct task_struct * __cpuinit idle_thread_get(unsigned int cpu) 20 { 21 struct task_struct *tsk = per_cpu(idle_threads, cpu); 22 23 if (!tsk) 24 return ERR_PTR(-ENOMEM); 25 init_idle(tsk, cpu); 26 return tsk; 27 } 28 29 void __init idle_thread_set_boot_cpu(void) 30 { 31 per_cpu(idle_threads, smp_processor_id()) = current; 32 } 33 34 static inline void idle_init(unsigned int cpu) 35 { 36 struct task_struct *tsk = per_cpu(idle_threads, cpu); 37 38 if (!tsk) { 39 tsk = fork_idle(cpu); 40 if (IS_ERR(tsk)) 41 pr_err("SMP: fork_idle() failed for CPU %u\n", cpu); 42 else 43 per_cpu(idle_threads, cpu) = tsk; 44 } 45 } 46 47 /** 48 * idle_thread_init - Initialize the idle thread for a cpu 49 * @cpu: The cpu for which the idle thread should be initialized 50 * 51 * Creates the thread if it does not exist. 52 */ 53 void __init idle_threads_init(void) 54 { 55 unsigned int cpu; 56 57 for_each_possible_cpu(cpu) { 58 if (cpu != smp_processor_id()) 59 idle_init(cpu); 60 } 61 } 62 #endif 63