kernel/cpu.c

   1 /* CPU control.
   2  * (C) 2001, 2002, 2003, 2004 Rusty Russell
   3  *
   4  * This code is licenced under the GPL.
   5  */
   6 #include <linux/proc_fs.h>
   7 #include <linux/smp.h>
   8 #include <linux/init.h>
   9 #include <linux/notifier.h>
  10 #include <linux/sched.h>
  11 #include <linux/unistd.h>
  12 #include <linux/cpu.h>
  13 #include <linux/module.h>
  14 #include <linux/kthread.h>
  15 #include <linux/stop_machine.h>
  16 #include <linux/mutex.h>
  17
  18 /* This protects CPUs going up and down... */
  19 static DEFINE_MUTEX(cpu_add_remove_lock);
  20 static DEFINE_MUTEX(cpu_bitmask_lock);
  21
  22 static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain);
  23
  24 #ifdef CONFIG_HOTPLUG_CPU
  25
  26 /* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */
  27 static struct task_struct *recursive;
  28 static int recursive_depth;
  29
  30 void lock_cpu_hotplug(void)
  31 {
  32         struct task_struct *tsk = current;
  33
  34         if (tsk == recursive) {
  35                 static int warnings = 10;
  36                 if (warnings) {
  37                         printk(KERN_ERR "Lukewarm IQ detected in hotplug locking\n");
  38                         WARN_ON(1);
  39                         warnings--;
  40                 }
  41                 recursive_depth++;
  42                 return;
  43         }
  44         mutex_lock(&cpu_bitmask_lock);
  45         recursive = tsk;
  46 }
  47 EXPORT_SYMBOL_GPL(lock_cpu_hotplug);
  48
  49 void unlock_cpu_hotplug(void)
  50 {
  51         WARN_ON(recursive != current);
  52         if (recursive_depth) {
  53                 recursive_depth--;
  54                 return;
  55         }
  56         mutex_unlock(&cpu_bitmask_lock);
  57         recursive = NULL;
  58 }
  59 EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
  60
  61 #endif  /* CONFIG_HOTPLUG_CPU */
  62
  63 /* Need to know about CPUs going up/down? */
  64 int __cpuinit register_cpu_notifier(struct notifier_block *nb)
  65 {
  66         return blocking_notifier_chain_register(&cpu_chain, nb);
  67 }
  68
  69 #ifdef CONFIG_HOTPLUG_CPU
  70
  71 EXPORT_SYMBOL(register_cpu_notifier);
  72
  73 void unregister_cpu_notifier(struct notifier_block *nb)
  74 {
  75         blocking_notifier_chain_unregister(&cpu_chain, nb);
  76 }
  77 EXPORT_SYMBOL(unregister_cpu_notifier);
  78
  79 static inline void check_for_tasks(int cpu)
  80 {
  81         struct task_struct *p;
  82
  83         write_lock_irq(&tasklist_lock);
  84         for_each_process(p) {
  85                 if (task_cpu(p) == cpu &&
  86                     (!cputime_eq(p->utime, cputime_zero) ||
  87                      !cputime_eq(p->stime, cputime_zero)))
  88                         printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
  89                                 (state = %ld, flags = %lx) \n",
  90                                  p->comm, p->pid, cpu, p->state, p->flags);
  91         }
  92         write_unlock_irq(&tasklist_lock);
  93 }
  94
  95 /* Take this CPU down. */
  96 static int take_cpu_down(void *unused)
  97 {
  98         int err;
  99
 100         /* Ensure this CPU doesn't handle any more interrupts. */
 101         err = __cpu_disable();
 102         if (err < 0)
 103                 return err;
 104
 105         /* Force idle task to run as soon as we yield: it should
 106            immediately notice cpu is offline and die quickly. */
 107         sched_idle_next();
 108         return 0;
 109 }
 110
 111 int cpu_down(unsigned int cpu)
 112 {
 113         int err;
 114         struct task_struct *p;
 115         cpumask_t old_allowed, tmp;
 116
 117         mutex_lock(&cpu_add_remove_lock);
 118         if (num_online_cpus() == 1) {
 119                 err = -EBUSY;
 120                 goto out;
 121         }
 122
 123         if (!cpu_online(cpu)) {
 124                 err = -EINVAL;
 125                 goto out;
 126         }
 127
 128         err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
 129                                                 (void *)(long)cpu);
 130         if (err == NOTIFY_BAD) {
 131                 printk("%s: attempt to take down CPU %u failed\n",
 132                                 __FUNCTION__, cpu);
 133                 err = -EINVAL;
 134                 goto out;
 135         }
 136
 137         /* Ensure that we are not runnable on dying cpu */
 138         old_allowed = current->cpus_allowed;
 139         tmp = CPU_MASK_ALL;
 140         cpu_clear(cpu, tmp);
 141         set_cpus_allowed(current, tmp);
 142
 143         mutex_lock(&cpu_bitmask_lock);
 144         p = __stop_machine_run(take_cpu_down, NULL, cpu);
 145         mutex_unlock(&cpu_bitmask_lock);
 146
 147         if (IS_ERR(p)) {
 148                 /* CPU didn't die: tell everyone.  Can't complain. */
 149                 if (blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
 150                                 (void *)(long)cpu) == NOTIFY_BAD)
 151                         BUG();
 152
 153                 err = PTR_ERR(p);
 154                 goto out_allowed;
 155         }
 156
 157         if (cpu_online(cpu))
 158                 goto out_thread;
 159
 160         /* Wait for it to sleep (leaving idle task). */
 161         while (!idle_cpu(cpu))
 162                 yield();
 163
 164         /* This actually kills the CPU. */
 165         __cpu_die(cpu);
 166
 167         /* Move it here so it can run. */
 168         kthread_bind(p, get_cpu());
 169         put_cpu();
 170
 171         /* CPU is completely dead: tell everyone.  Too late to complain. */
 172         if (blocking_notifier_call_chain(&cpu_chain, CPU_DEAD,
 173                         (void *)(long)cpu) == NOTIFY_BAD)
 174                 BUG();
 175
 176         check_for_tasks(cpu);
 177
 178 out_thread:
 179         err = kthread_stop(p);
 180 out_allowed:
 181         set_cpus_allowed(current, old_allowed);
 182 out:
 183         mutex_unlock(&cpu_add_remove_lock);
 184         return err;
 185 }
 186 #endif /*CONFIG_HOTPLUG_CPU*/
 187
 188 int __devinit cpu_up(unsigned int cpu)
 189 {
 190         int ret;
 191         void *hcpu = (void *)(long)cpu;
 192
 193         mutex_lock(&cpu_add_remove_lock);
 194         if (cpu_online(cpu) || !cpu_present(cpu)) {
 195                 ret = -EINVAL;
 196                 goto out;
 197         }
 198
 199         ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
 200         if (ret == NOTIFY_BAD) {
 201                 printk("%s: attempt to bring up CPU %u failed\n",
 202                                 __FUNCTION__, cpu);
 203                 ret = -EINVAL;
 204                 goto out_notify;
 205         }
 206
 207         /* Arch-specific enabling code. */
 208         mutex_lock(&cpu_bitmask_lock);
 209         ret = __cpu_up(cpu);
 210         mutex_unlock(&cpu_bitmask_lock);
 211         if (ret != 0)
 212                 goto out_notify;
 213         BUG_ON(!cpu_online(cpu));
 214
 215         /* Now call notifier in preparation. */
 216         blocking_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
 217
 218 out_notify:
 219         if (ret != 0)
 220                 blocking_notifier_call_chain(&cpu_chain,
 221                                 CPU_UP_CANCELED, hcpu);
 222 out:
 223         mutex_unlock(&cpu_add_remove_lock);
 224         return ret;
 225 }