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