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, task_pid_nr(p), cpu, 102 p->state, p->flags); 103 } 104 write_unlock_irq(&tasklist_lock); 105 } 106 107 struct take_cpu_down_param { 108 unsigned long mod; 109 void *hcpu; 110 }; 111 112 /* Take this CPU down. */ 113 static int take_cpu_down(void *_param) 114 { 115 struct take_cpu_down_param *param = _param; 116 int err; 117 118 raw_notifier_call_chain(&cpu_chain, CPU_DYING | param->mod, 119 param->hcpu); 120 /* Ensure this CPU doesn't handle any more interrupts. */ 121 err = __cpu_disable(); 122 if (err < 0) 123 return err; 124 125 /* Force idle task to run as soon as we yield: it should 126 immediately notice cpu is offline and die quickly. */ 127 sched_idle_next(); 128 return 0; 129 } 130 131 /* Requires cpu_add_remove_lock to be held */ 132 static int _cpu_down(unsigned int cpu, int tasks_frozen) 133 { 134 int err, nr_calls = 0; 135 struct task_struct *p; 136 cpumask_t old_allowed, tmp; 137 void *hcpu = (void *)(long)cpu; 138 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0; 139 struct take_cpu_down_param tcd_param = { 140 .mod = mod, 141 .hcpu = hcpu, 142 }; 143 144 if (num_online_cpus() == 1) 145 return -EBUSY; 146 147 if (!cpu_online(cpu)) 148 return -EINVAL; 149 150 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu); 151 err = __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE | mod, 152 hcpu, -1, &nr_calls); 153 if (err == NOTIFY_BAD) { 154 nr_calls--; 155 __raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod, 156 hcpu, nr_calls, NULL); 157 printk("%s: attempt to take down CPU %u failed\n", 158 __FUNCTION__, cpu); 159 err = -EINVAL; 160 goto out_release; 161 } 162 163 /* Ensure that we are not runnable on dying cpu */ 164 old_allowed = current->cpus_allowed; 165 tmp = CPU_MASK_ALL; 166 cpu_clear(cpu, tmp); 167 set_cpus_allowed(current, tmp); 168 169 mutex_lock(&cpu_bitmask_lock); 170 p = __stop_machine_run(take_cpu_down, &tcd_param, cpu); 171 mutex_unlock(&cpu_bitmask_lock); 172 173 if (IS_ERR(p) || cpu_online(cpu)) { 174 /* CPU didn't die: tell everyone. Can't complain. */ 175 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED | mod, 176 hcpu) == NOTIFY_BAD) 177 BUG(); 178 179 if (IS_ERR(p)) { 180 err = PTR_ERR(p); 181 goto out_allowed; 182 } 183 goto out_thread; 184 } 185 186 /* Wait for it to sleep (leaving idle task). */ 187 while (!idle_cpu(cpu)) 188 yield(); 189 190 /* This actually kills the CPU. */ 191 __cpu_die(cpu); 192 193 /* CPU is completely dead: tell everyone. Too late to complain. */ 194 if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD | mod, 195 hcpu) == NOTIFY_BAD) 196 BUG(); 197 198 check_for_tasks(cpu); 199 200 out_thread: 201 err = kthread_stop(p); 202 out_allowed: 203 set_cpus_allowed(current, old_allowed); 204 out_release: 205 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu); 206 return err; 207 } 208 209 int cpu_down(unsigned int cpu) 210 { 211 int err = 0; 212 213 mutex_lock(&cpu_add_remove_lock); 214 if (cpu_hotplug_disabled) 215 err = -EBUSY; 216 else 217 err = _cpu_down(cpu, 0); 218 219 mutex_unlock(&cpu_add_remove_lock); 220 return err; 221 } 222 #endif /*CONFIG_HOTPLUG_CPU*/ 223 224 /* Requires cpu_add_remove_lock to be held */ 225 static int __cpuinit _cpu_up(unsigned int cpu, int tasks_frozen) 226 { 227 int ret, nr_calls = 0; 228 void *hcpu = (void *)(long)cpu; 229 unsigned long mod = tasks_frozen ? CPU_TASKS_FROZEN : 0; 230 231 if (cpu_online(cpu) || !cpu_present(cpu)) 232 return -EINVAL; 233 234 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_ACQUIRE, hcpu); 235 ret = __raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE | mod, hcpu, 236 -1, &nr_calls); 237 if (ret == NOTIFY_BAD) { 238 nr_calls--; 239 printk("%s: attempt to bring up CPU %u failed\n", 240 __FUNCTION__, cpu); 241 ret = -EINVAL; 242 goto out_notify; 243 } 244 245 /* Arch-specific enabling code. */ 246 mutex_lock(&cpu_bitmask_lock); 247 ret = __cpu_up(cpu); 248 mutex_unlock(&cpu_bitmask_lock); 249 if (ret != 0) 250 goto out_notify; 251 BUG_ON(!cpu_online(cpu)); 252 253 /* Now call notifier in preparation. */ 254 raw_notifier_call_chain(&cpu_chain, CPU_ONLINE | mod, hcpu); 255 256 out_notify: 257 if (ret != 0) 258 __raw_notifier_call_chain(&cpu_chain, 259 CPU_UP_CANCELED | mod, hcpu, nr_calls, NULL); 260 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu); 261 262 return ret; 263 } 264 265 int __cpuinit cpu_up(unsigned int cpu) 266 { 267 int err = 0; 268 if (!cpu_isset(cpu, cpu_possible_map)) { 269 printk(KERN_ERR "can't online cpu %d because it is not " 270 "configured as may-hotadd at boot time\n", cpu); 271 #if defined(CONFIG_IA64) || defined(CONFIG_X86_64) || defined(CONFIG_S390) 272 printk(KERN_ERR "please check additional_cpus= boot " 273 "parameter\n"); 274 #endif 275 return -EINVAL; 276 } 277 278 mutex_lock(&cpu_add_remove_lock); 279 if (cpu_hotplug_disabled) 280 err = -EBUSY; 281 else 282 err = _cpu_up(cpu, 0); 283 284 mutex_unlock(&cpu_add_remove_lock); 285 return err; 286 } 287 288 #ifdef CONFIG_PM_SLEEP_SMP 289 static cpumask_t frozen_cpus; 290 291 int disable_nonboot_cpus(void) 292 { 293 int cpu, first_cpu, error = 0; 294 295 mutex_lock(&cpu_add_remove_lock); 296 first_cpu = first_cpu(cpu_online_map); 297 /* We take down all of the non-boot CPUs in one shot to avoid races 298 * with the userspace trying to use the CPU hotplug at the same time 299 */ 300 cpus_clear(frozen_cpus); 301 printk("Disabling non-boot CPUs ...\n"); 302 for_each_online_cpu(cpu) { 303 if (cpu == first_cpu) 304 continue; 305 error = _cpu_down(cpu, 1); 306 if (!error) { 307 cpu_set(cpu, frozen_cpus); 308 printk("CPU%d is down\n", cpu); 309 } else { 310 printk(KERN_ERR "Error taking CPU%d down: %d\n", 311 cpu, error); 312 break; 313 } 314 } 315 if (!error) { 316 BUG_ON(num_online_cpus() > 1); 317 /* Make sure the CPUs won't be enabled by someone else */ 318 cpu_hotplug_disabled = 1; 319 } else { 320 printk(KERN_ERR "Non-boot CPUs are not disabled\n"); 321 } 322 mutex_unlock(&cpu_add_remove_lock); 323 return error; 324 } 325 326 void enable_nonboot_cpus(void) 327 { 328 int cpu, error; 329 330 /* Allow everyone to use the CPU hotplug again */ 331 mutex_lock(&cpu_add_remove_lock); 332 cpu_hotplug_disabled = 0; 333 if (cpus_empty(frozen_cpus)) 334 goto out; 335 336 printk("Enabling non-boot CPUs ...\n"); 337 for_each_cpu_mask(cpu, frozen_cpus) { 338 error = _cpu_up(cpu, 1); 339 if (!error) { 340 printk("CPU%d is up\n", cpu); 341 continue; 342 } 343 printk(KERN_WARNING "Error taking CPU%d up: %d\n", cpu, error); 344 } 345 cpus_clear(frozen_cpus); 346 out: 347 mutex_unlock(&cpu_add_remove_lock); 348 } 349 #endif /* CONFIG_PM_SLEEP_SMP */ 350