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   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 = %x) \n",
 101                                  p->comm, p->pid, cpu, p->state, p->flags);
 102         }
 103         write_unlock_irq(&tasklist_lock);
 104 }
 105
 106 struct take_cpu_down_param {
 107         unsigned long mod;
 108         void *hcpu;
 109 };
 110
 111 /* Take this CPU down. */
 112 static int take_cpu_down(void *_param)
 113 {
 114         struct take_cpu_down_param *param = _param;
 115         int err;
 116
 117         raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod,
 118                                 param->hcpu);
 119         /* Ensure this CPU doesn't handle any more interrupts. */
 120         err = __cpu_disable();
 121         if (err < 0)
 122                 return err;
 123
 124         /* Force idle task to run as soon as we yield: it should
 125            immediately notice cpu is offline and die quickly. */
 126         sched_idle_next();
 127         return 0;
 128 }
 129
 130 /* Requires cpu_add_remove_lock to be held */
 131 static int _cpu_down(unsigned int cpu, int tasks_frozen)
 132 {
 133         int err, nr_calls = 0;
 134         struct task_struct *p;
 135         cpumask_t old_allowed, tmp;
 136         void *hcpu = (void *)(long)cpu;
 137         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
 138         struct take_cpu_down_param tcd_param = {
 139                 .mod = mod,
 140                 .hcpu = hcpu,
 141         };
 142
 143         if (num_online_cpus() == 1)
 144                 return -EBUSY;
 145
 146         if (!cpu_online(cpu))
 147                 return -EINVAL;
 148
 149         raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
 150         err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod,
 151                                         hcpu, -1, &nr_calls);
 152         if (err == NOTIFY_BAD) {
 153                 nr_calls--;
 154                 __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
 155                                           hcpu, nr_calls, NULL);
 156                 printk("%s: attempt to take down CPU %u failed\n",
 157                                 __FUNCTION__, cpu);
 158                 err = -EINVAL;
 159                 goto out_release;
 160         }
 161
 162         /* Ensure that we are not runnable on dying cpu */
 163         old_allowed = current->cpus_allowed;
 164         tmp = CPU_MASK_ALL;
 165         cpu_clear(cpu, tmp);
 166         set_cpus_allowed(current, tmp);
 167
 168         mutex_lock(&cpu_bitmask_lock);
 169         p = __stop_machine_run(take_cpu_down, &tcd_param, cpu);
 170         mutex_unlock(&cpu_bitmask_lock);
 171
 172         if (IS_ERR(p) || cpu_online(cpu)) {
 173                 /* CPU didn't die: tell everyone.  Can't complain. */
 174                 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod,
 175                                             hcpu) == NOTIFY_BAD)
 176                         BUG();
 177
 178                 if (IS_ERR(p)) {
 179                         err = PTR_ERR(p);
 180                         goto out_allowed;
 181                 }
 182                 goto out_thread;
 183         }
 184
 185         /* Wait for it to sleep (leaving idle task). */
 186         while (!idle_cpu(cpu))
 187                 yield();
 188
 189         /* This actually kills the CPU. */
 190         __cpu_die(cpu);
 191
 192         /* CPU is completely dead: tell everyone.  Too late to complain. */
 193         if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod,
 194                                     hcpu) == NOTIFY_BAD)
 195                 BUG();
 196
 197         check_for_tasks(cpu);
 198
 199 out_thread:
 200         err = kthread_stop(p);
 201 out_allowed:
 202         set_cpus_allowed(current, old_allowed);
 203 out_release:
 204         raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
 205         return err;
 206 }
 207
 208 int cpu_down(unsigned int cpu)
 209 {
 210         int err = 0;
 211
 212         mutex_lock(&cpu_add_remove_lock);
 213         if (cpu_hotplug_disabled)
 214                 err = -EBUSY;
 215         else
 216                 err = _cpu_down(cpu, 0);
 217
 218         mutex_unlock(&cpu_add_remove_lock);
 219         return err;
 220 }
 221 #endif /*CONFIG_HOTPLUG_CPU*/
 222
 223 /* Requires cpu_add_remove_lock to be held */
 224 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen)
 225 {
 226         int ret, nr_calls = 0;
 227         void *hcpu = (void *)(long)cpu;
 228         unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0;
 229
 230         if (cpu_online(cpu) || !cpu_present(cpu))
 231                 return -EINVAL;
 232
 233         raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu);
 234         ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu,
 235                                                         -1, &nr_calls);
 236         if (ret == NOTIFY_BAD) {
 237                 nr_calls--;
 238                 printk("%s: attempt to bring up CPU %u failed\n",
 239                                 __FUNCTION__, cpu);
 240                 ret = -EINVAL;
 241                 goto out_notify;
 242         }
 243
 244         /* Arch-specific enabling code. */
 245         mutex_lock(&cpu_bitmask_lock);
 246         ret = __cpu_up(cpu);
 247         mutex_unlock(&cpu_bitmask_lock);
 248         if (ret != 0)
 249                 goto out_notify;
 250         BUG_ON(!cpu_online(cpu));
 251
 252         /* Now call notifier in preparation. */
 253         raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu);
 254
 255 out_notify:
 256         if (ret != 0)
 257                 __raw_notifier_call_chain(&cpu_chain,
 258                                 CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL);
 259         raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
 260
 261         return ret;
 262 }
 263
 264 int __cpuinit cpu_up(unsigned int cpu)
 265 {
 266         int err = 0;
 267
 268         mutex_lock(&cpu_add_remove_lock);
 269         if (cpu_hotplug_disabled)
 270                 err = -EBUSY;
 271         else
 272                 err = _cpu_up(cpu, 0);
 273
 274         mutex_unlock(&cpu_add_remove_lock);
 275         return err;
 276 }
 277
 278 #ifdef CONFIG_PM_SLEEP_SMP
 279 static cpumask_t frozen_cpus;
 280
 281 int disable_nonboot_cpus(void)
 282 {
 283         int cpu, first_cpu, error = 0;
 284
 285         mutex_lock(&cpu_add_remove_lock);
 286         first_cpu = first_cpu(cpu_online_map);
 287         /* We take down all of the non-boot CPUs in one shot to avoid races
 288          * with the userspace trying to use the CPU hotplug at the same time
 289          */
 290         cpus_clear(frozen_cpus);
 291         printk("Disabling non-boot CPUs ...\n");
 292         for_each_online_cpu(cpu) {
 293                 if (cpu == first_cpu)
 294                         continue;
 295                 error = _cpu_down(cpu, 1);
 296                 if (!error) {
 297                         cpu_set(cpu, frozen_cpus);
 298                         printk("CPU%d is down\n", cpu);
 299                 } else {
 300                         printk(KERN_ERR "Error taking CPU%d down: %d\n",
 301                                 cpu, error);
 302                         break;
 303                 }
 304         }
 305         if (!error) {
 306                 BUG_ON(num_online_cpus() > 1);
 307                 /* Make sure the CPUs won't be enabled by someone else */
 308                 cpu_hotplug_disabled = 1;
 309         } else {
 310                 printk(KERN_ERR "Non-boot CPUs are not disabled\n");
 311         }
 312         mutex_unlock(&cpu_add_remove_lock);
 313         return error;
 314 }
 315
 316 void enable_nonboot_cpus(void)
 317 {
 318         int cpu, error;
 319
 320         /* Allow everyone to use the CPU hotplug again */
 321         mutex_lock(&cpu_add_remove_lock);
 322         cpu_hotplug_disabled = 0;
 323         if (cpus_empty(frozen_cpus))
 324                 goto out;
 325
 326         printk("Enabling non-boot CPUs ...\n");
 327         for_each_cpu_mask(cpu, frozen_cpus) {
 328                 error = _cpu_up(cpu, 1);
 329                 if (!error) {
 330                         printk("CPU%d is up\n", cpu);
 331                         continue;
 332                 }
 333                 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error);
 334         }
 335         cpus_clear(frozen_cpus);
 336 out:
 337         mutex_unlock(&cpu_add_remove_lock);
 338 }
 339 #endif /* CONFIG_PM_SLEEP_SMP */