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 */ 340