kernel/smpboot.c

   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, boot_cpu;
  56
  57         boot_cpu = smp_processor_id();
  58
  59         for_each_possible_cpu(cpu) {
  60                 if (cpu != boot_cpu)
  61                         idle_init(cpu);
  62         }
  63 }
  64 #endif