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 /**
  35  * idle_init - Initialize the idle thread for a cpu
  36  * @cpu:        The cpu for which the idle thread should be initialized
  37  *
  38  * Creates the thread if it does not exist.
  39  */
  40 static inline void idle_init(unsigned int cpu)
  41 {
  42         struct task_struct *tsk = per_cpu(idle_threads, cpu);
  43
  44         if (!tsk) {
  45                 tsk = fork_idle(cpu);
  46                 if (IS_ERR(tsk))
  47                         pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
  48                 else
  49                         per_cpu(idle_threads, cpu) = tsk;
  50         }
  51 }
  52
  53 /**
  54  * idle_threads_init - Initialize idle threads for all cpus
  55  */
  56 void __init idle_threads_init(void)
  57 {
  58         unsigned int cpu, boot_cpu;
  59
  60         boot_cpu = smp_processor_id();
  61
  62         for_each_possible_cpu(cpu) {
  63                 if (cpu != boot_cpu)
  64                         idle_init(cpu);
  65         }
  66 }
  67 #endif