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 RAW_NOTIFIER_HEAD(cpu_chain);
  23
  24 /* If set, cpu_up and cpu_down will return -EBUSY and do nothing.
  25  * Should always be manipulated under cpu_add_remove_lock
  26  */
  27 static int cpu_hotplug_disabled;
  28
  29 #ifdef CONFIG_HOTPLUG_CPU
  30
  31 /* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */
  32 static struct task_struct *recursive;
  33 static int recursive_depth;
  34
  35 void lock_cpu_hotplug(void)
  36 {
  37         struct task_struct *tsk = current;
  38
  39         if (tsk == recursive) {
  40                 static int warnings = 10;
  41                 if (warnings) {
  42                         printk(KERN_ERR "Lukewarm IQ detected in hotplug locking\n");
  43                         WARN_ON(1);
  44                         warnings--;
  45                 }
  46                 recursive_depth++;
  47                 return;
  48         }
  49         mutex_lock(&cpu_bitmask_lock);
  50         recursive = tsk;
  51 }
  52 EXPORT_SYMBOL_GPL(lock_cpu_hotplug);
  53
  54 void unlock_cpu_hotplug(void)
  55 {
  56         WARN_ON(recursive != current);
  57         if (recursive_depth) {
  58                 recursive_depth--;
  59                 return;
  60         }
  61         recursive = NULL;
  62         mutex_unlock(&cpu_bitmask_lock);
  63 }
  64 EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
  65
  66 #endif  /* CONFIG_HOTPLUG_CPU */
  67
  68 /* Need to know about CPUs going up/down? */
  69 int __cpuinit register_cpu_notifier(struct notifier_block *nb)
  70 {
  71         int ret;
  72         mutex_lock(&cpu_add_remove_lock);
  73         ret = raw_notifier_chain_register(&cpu_chain, nb);
  74         mutex_unlock(&cpu_add_remove_lock);
  75         return ret;
  76 }
  77
  78 #ifdef CONFIG_HOTPLUG_CPU
  79
  80 EXPORT_SYMBOL(register_cpu_notifier);
  81
  82 void unregister_cpu_notifier(struct notifier_block *nb)
  83 {
  84         mutex_lock(&cpu_add_remove_lock);
  85         raw_notifier_chain_unregister(&cpu_chain, nb);
  86         mutex_unlock(&cpu_add_remove_lock);
  87 }
  88 EXPORT_SYMBOL(unregister_cpu_notifier);
  89
  90 static inline void check_for_tasks(int cpu)
  91 {
  92         struct task_struct *p;
  93
  94         write_lock_irq(&tasklist_lock);
  95         for_each_process(p) {
  96                 if (task_cpu(p) == cpu &&
  97                     (!cputime_eq(p->utime, cputime_zero) ||
  98                      !cputime_eq(p->stime, cputime_zero)))
  99                         printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
 100                                 (state = %ld, flags = %lx) \n",
 101                                  p->comm, p->pid, cpu, p->state, p->flags);
 102         }
 103         write_unlock_irq(&tasklist_lock);
 104 }
 105
 106 /* Take this CPU down. */
 107 static int take_cpu_down(void *unused)
 108 {
 109         int err;
 110
 111         /* Ensure this CPU doesn't handle any more interrupts. */
 112         err = __cpu_disable();
 113         if (err < 0)
 114                 return err;
 115
 116         /* Force idle task to run as soon as we yield: it should
 117            immediately notice cpu is offline and die quickly. */
 118         sched_idle_next();
 119         return 0;
 120 }
 121
 122 /* Requires cpu_add_remove_lock to be held */
 123 static int _cpu_down(unsigned int cpu)
 124 {
 125         int err;
 126         struct task_struct *p;
 127         cpumask_t old_allowed, tmp;
 128
 129         if (num_online_cpus() == 1)
 130                 return -EBUSY;
 131
 132         if (!cpu_online(cpu))
 133                 return -EINVAL;
 134
 135         raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE,
 136                                                 (void *)(long)cpu);
 137         err = raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
 138                                                 (void *)(long)cpu);
 139         if (err == NOTIFY_BAD) {
 140                 printk("%s: attempt to take down CPU %u failed\n",
 141                                 __FUNCTION__, cpu);
 142                 err = -EINVAL;
 143                 goto out_release;
 144         }
 145
 146         /* Ensure that we are not runnable on dying cpu */
 147         old_allowed = current->cpus_allowed;
 148         tmp = CPU_MASK_ALL;
 149         cpu_clear(cpu, tmp);
 150         set_cpus_allowed(current, tmp);
 151
 152         mutex_lock(&cpu_bitmask_lock);
 153         p = __stop_machine_run(take_cpu_down, NULL, cpu);
 154         mutex_unlock(&cpu_bitmask_lock);
 155
 156         if (IS_ERR(p) || cpu_online(cpu)) {
 157                 /* CPU didn't die: tell everyone.  Can't complain. */
 158                 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
 159                                 (void *)(long)cpu) == NOTIFY_BAD)
 160                         BUG();
 161
 162                 if (IS_ERR(p)) {
 163                         err = PTR_ERR(p);
 164                         goto out_allowed;
 165                 }
 166                 goto out_thread;
 167         }
 168
 169         /* Wait for it to sleep (leaving idle task). */
 170         while (!idle_cpu(cpu))
 171                 yield();
 172
 173         /* This actually kills the CPU. */
 174         __cpu_die(cpu);
 175
 176         /* Move it here so it can run. */
 177         kthread_bind(p, get_cpu());
 178         put_cpu();
 179
 180         /* CPU is completely dead: tell everyone.  Too late to complain. */
 181         if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD,
 182                         (void *)(long)cpu) == NOTIFY_BAD)
 183                 BUG();
 184
 185         check_for_tasks(cpu);
 186
 187 out_thread:
 188         err = kthread_stop(p);
 189 out_allowed:
 190         set_cpus_allowed(current, old_allowed);
 191 out_release:
 192         raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE,
 193                                                 (void *)(long)cpu);
 194         return err;
 195 }
 196
 197 int cpu_down(unsigned int cpu)
 198 {
 199         int err = 0;
 200
 201         mutex_lock(&cpu_add_remove_lock);
 202         if (cpu_hotplug_disabled)
 203                 err = -EBUSY;
 204         else
 205                 err = _cpu_down(cpu);
 206
 207         mutex_unlock(&cpu_add_remove_lock);
 208         return err;
 209 }
 210 #endif /*CONFIG_HOTPLUG_CPU*/
 211
 212 /* Requires cpu_add_remove_lock to be held */
 213 static int __cpuinit _cpu_up(unsigned int cpu)
 214 {
 215         int ret, nr_calls = 0;
 216         void *hcpu = (void *)(long)cpu;
 217
 218         if (cpu_online(cpu) || !cpu_present(cpu))
 219                 return -EINVAL;
 220
 221         raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
 222         ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu,
 223                                                         -1, &nr_calls);
 224         if (ret == NOTIFY_BAD) {
 225                 printk("%s: attempt to bring up CPU %u failed\n",
 226                                 __FUNCTION__, cpu);
 227                 ret = -EINVAL;
 228                 goto out_notify;
 229         }
 230
 231         /* Arch-specific enabling code. */
 232         mutex_lock(&cpu_bitmask_lock);
 233         ret = __cpu_up(cpu);
 234         mutex_unlock(&cpu_bitmask_lock);
 235         if (ret != 0)
 236                 goto out_notify;
 237         BUG_ON(!cpu_online(cpu));
 238
 239         /* Now call notifier in preparation. */
 240         raw_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
 241
 242 out_notify:
 243         if (ret != 0)
 244                 __raw_notifier_call_chain(&cpu_chain,
 245                                 CPU_UP_CANCELED, hcpu, nr_calls, NULL);
 246         raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
 247
 248         return ret;
 249 }
 250
 251 int __cpuinit cpu_up(unsigned int cpu)
 252 {
 253         int err = 0;
 254
 255         mutex_lock(&cpu_add_remove_lock);
 256         if (cpu_hotplug_disabled)
 257                 err = -EBUSY;
 258         else
 259                 err = _cpu_up(cpu);
 260
 261         mutex_unlock(&cpu_add_remove_lock);
 262         return err;
 263 }
 264
 265 #ifdef CONFIG_SUSPEND_SMP
 266 /* Needed to prevent the microcode driver from requesting firmware in its CPU
 267  * hotplug notifier during the suspend/resume.
 268  */
 269 int suspend_cpu_hotplug;
 270 EXPORT_SYMBOL(suspend_cpu_hotplug);
 271
 272 static cpumask_t frozen_cpus;
 273
 274 int disable_nonboot_cpus(void)
 275 {
 276         int cpu, first_cpu, error = 0;
 277
 278         mutex_lock(&cpu_add_remove_lock);
 279         suspend_cpu_hotplug = 1;
 280         first_cpu = first_cpu(cpu_online_map);
 281         /* We take down all of the non-boot CPUs in one shot to avoid races
 282          * with the userspace trying to use the CPU hotplug at the same time
 283          */
 284         cpus_clear(frozen_cpus);
 285         printk("Disabling non-boot CPUs ...\n");
 286         for_each_online_cpu(cpu) {
 287                 if (cpu == first_cpu)
 288                         continue;
 289                 error = _cpu_down(cpu);
 290                 if (!error) {
 291                         cpu_set(cpu, frozen_cpus);
 292                         printk("CPU%d is down\n", cpu);
 293                 } else {
 294                         printk(KERN_ERR "Error taking CPU%d down: %d\n",
 295                                 cpu, error);
 296                         break;
 297                 }
 298         }
 299         if (!error) {
 300                 BUG_ON(num_online_cpus() > 1);
 301                 /* Make sure the CPUs won't be enabled by someone else */
 302                 cpu_hotplug_disabled = 1;
 303         } else {
 304                 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
 305         }
 306         suspend_cpu_hotplug = 0;
 307         mutex_unlock(&cpu_add_remove_lock);
 308         return error;
 309 }
 310
 311 void enable_nonboot_cpus(void)
 312 {
 313         int cpu, error;
 314
 315         /* Allow everyone to use the CPU hotplug again */
 316         mutex_lock(&cpu_add_remove_lock);
 317         cpu_hotplug_disabled = 0;
 318         if (cpus_empty(frozen_cpus))
 319                 goto out;
 320
 321         suspend_cpu_hotplug = 1;
 322         printk("Enabling non-boot CPUs ...\n");
 323         for_each_cpu_mask(cpu, frozen_cpus) {
 324                 error = _cpu_up(cpu);
 325                 if (!error) {
 326                         printk("CPU%d is up\n", cpu);
 327                         continue;
 328                 }
 329                 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
 330         }
 331         cpus_clear(frozen_cpus);
 332         suspend_cpu_hotplug = 0;
 333 out:
 334         mutex_unlock(&cpu_add_remove_lock);
 335 }
 336 #endif