kernel/cpu.c

   1 /* CPU control.
   2  * (C) 2001 Rusty Russell
   3  * This code is licenced under the GPL.
   4  */
   5 #include <linux/proc_fs.h>
   6 #include <linux/smp.h>
   7 #include <linux/init.h>
   8 #include <linux/notifier.h>
   9 #include <linux/sched.h>
  10 #include <linux/unistd.h>
  11 #include <asm/semaphore.h>
  12
  13 /* This protects CPUs going up and down... */
  14 DECLARE_MUTEX(cpucontrol);
  15
  16 static struct notifier_block *cpu_chain = NULL;
  17
  18 /* Need to know about CPUs going up/down? */
  19 int register_cpu_notifier(struct notifier_block *nb)
  20 {
  21         return notifier_chain_register(&cpu_chain, nb);
  22 }
  23
  24 void unregister_cpu_notifier(struct notifier_block *nb)
  25 {
  26         notifier_chain_unregister(&cpu_chain,nb);
  27 }
  28
  29 int __devinit cpu_up(unsigned int cpu)
  30 {
  31         int ret;
  32
  33         if ((ret = down_interruptible(&cpucontrol)) != 0)
  34                 return ret;
  35
  36         if (cpu_online(cpu)) {
  37                 ret = -EINVAL;
  38                 goto out;
  39         }
  40
  41         /* Arch-specific enabling code. */
  42         ret = __cpu_up(cpu);
  43         if (ret != 0) goto out;
  44         if (!cpu_online(cpu))
  45                 BUG();
  46
  47         /* Now call notifier in preparation. */
  48         printk("CPU %u IS NOW UP!\n", cpu);
  49         notifier_call_chain(&cpu_chain, CPU_ONLINE, (void *)(long)cpu);
  50
  51  out:
  52         up(&cpucontrol);
  53         return ret;
  54 }