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         void *hcpu = (void *)(long)cpu;
  33
  34         if ((ret = down_interruptible(&cpucontrol)) != 0)
  35                 return ret;
  36
  37         if (cpu_online(cpu)) {
  38                 ret = -EINVAL;
  39                 goto out;
  40         }
  41         ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
  42         if (ret == NOTIFY_BAD) {
  43                 printk("%s: attempt to bring up CPU %u failed\n",
  44                                 __FUNCTION__, cpu);
  45                 ret = -EINVAL;
  46                 goto out_notify;
  47         }
  48
  49         /* Arch-specific enabling code. */
  50         ret = __cpu_up(cpu);
  51         if (ret != 0)
  52                 goto out_notify;
  53         if (!cpu_online(cpu))
  54                 BUG();
  55
  56         /* Now call notifier in preparation. */
  57         printk("CPU %u IS NOW UP!\n", cpu);
  58         notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
  59
  60 out_notify:
  61         if (ret != 0)
  62                 notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu);
  63 out:
  64         up(&cpucontrol);
  65         return ret;
  66 }