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 <linux/cpu.h>
  12 #include <asm/semaphore.h>
  13
  14 /* This protects CPUs going up and down... */
  15 DECLARE_MUTEX(cpucontrol);
  16
  17 static struct notifier_block *cpu_chain;
  18
  19 /* Need to know about CPUs going up/down? */
  20 int register_cpu_notifier(struct notifier_block *nb)
  21 {
  22         return notifier_chain_register(&cpu_chain, nb);
  23 }
  24
  25 void unregister_cpu_notifier(struct notifier_block *nb)
  26 {
  27         notifier_chain_unregister(&cpu_chain,nb);
  28 }
  29
  30 int __devinit cpu_up(unsigned int cpu)
  31 {
  32         int ret;
  33         void *hcpu = (void *)(long)cpu;
  34
  35         if ((ret = down_interruptible(&cpucontrol)) != 0)
  36                 return ret;
  37
  38         if (cpu_online(cpu)) {
  39                 ret = -EINVAL;
  40                 goto out;
  41         }
  42         ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
  43         if (ret == NOTIFY_BAD) {
  44                 printk("%s: attempt to bring up CPU %u failed\n",
  45                                 __FUNCTION__, cpu);
  46                 ret = -EINVAL;
  47                 goto out_notify;
  48         }
  49
  50         /* Arch-specific enabling code. */
  51         ret = __cpu_up(cpu);
  52         if (ret != 0)
  53                 goto out_notify;
  54         if (!cpu_online(cpu))
  55                 BUG();
  56
  57         /* Now call notifier in preparation. */
  58         printk("CPU %u IS NOW UP!\n", cpu);
  59         notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
  60
  61 out_notify:
  62         if (ret != 0)
  63                 notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu);
  64 out:
  65         up(&cpucontrol);
  66         return ret;
  67 }