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 err = raw_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE, 136 (void *)(long)cpu); 137 if (err == NOTIFY_BAD) { 138 printk("%s: attempt to take down CPU %u failed\n", 139 __FUNCTION__, cpu); 140 return -EINVAL; 141 } 142 143 /* Ensure that we are not runnable on dying cpu */ 144 old_allowed = current->cpus_allowed; 145 tmp = CPU_MASK_ALL; 146 cpu_clear(cpu, tmp); 147 set_cpus_allowed(current, tmp); 148 149 mutex_lock(&cpu_bitmask_lock); 150 p = __stop_machine_run(take_cpu_down, NULL, cpu); 151 mutex_unlock(&cpu_bitmask_lock); 152 153 if (IS_ERR(p) || cpu_online(cpu)) { 154 /* CPU didn't die: tell everyone. Can't complain. */ 155 if (raw_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED, 156 (void *)(long)cpu) == NOTIFY_BAD) 157 BUG(); 158 159 if (IS_ERR(p)) { 160 err = PTR_ERR(p); 161 goto out_allowed; 162 } 163 goto out_thread; 164 } 165 166 /* Wait for it to sleep (leaving idle task). */ 167 while (!idle_cpu(cpu)) 168 yield(); 169 170 /* This actually kills the CPU. */ 171 __cpu_die(cpu); 172 173 /* Move it here so it can run. */ 174 kthread_bind(p, get_cpu()); 175 put_cpu(); 176 177 /* CPU is completely dead: tell everyone. Too late to complain. */ 178 if (raw_notifier_call_chain(&cpu_chain, CPU_DEAD, 179 (void *)(long)cpu) == NOTIFY_BAD) 180 BUG(); 181 182 check_for_tasks(cpu); 183 184 out_thread: 185 err = kthread_stop(p); 186 out_allowed: 187 set_cpus_allowed(current, old_allowed); 188 return err; 189 } 190 191 int cpu_down(unsigned int cpu) 192 { 193 int err = 0; 194 195 mutex_lock(&cpu_add_remove_lock); 196 if (cpu_hotplug_disabled) 197 err = -EBUSY; 198 else 199 err = _cpu_down(cpu); 200 201 mutex_unlock(&cpu_add_remove_lock); 202 return err; 203 } 204 #endif /*CONFIG_HOTPLUG_CPU*/ 205 206 /* Requires cpu_add_remove_lock to be held */ 207 static int __cpuinit _cpu_up(unsigned int cpu) 208 { 209 int ret; 210 void *hcpu = (void *)(long)cpu; 211 212 if (cpu_online(cpu) || !cpu_present(cpu)) 213 return -EINVAL; 214 215 ret = raw_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu); 216 if (ret == NOTIFY_BAD) { 217 printk("%s: attempt to bring up CPU %u failed\n", 218 __FUNCTION__, cpu); 219 ret = -EINVAL; 220 goto out_notify; 221 } 222 223 /* Arch-specific enabling code. */ 224 mutex_lock(&cpu_bitmask_lock); 225 ret = __cpu_up(cpu); 226 mutex_unlock(&cpu_bitmask_lock); 227 if (ret != 0) 228 goto out_notify; 229 BUG_ON(!cpu_online(cpu)); 230 231 /* Now call notifier in preparation. */ 232 raw_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu); 233 234 out_notify: 235 if (ret != 0) 236 raw_notifier_call_chain(&cpu_chain, 237 CPU_UP_CANCELED, hcpu); 238 239 return ret; 240 } 241 242 int __cpuinit cpu_up(unsigned int cpu) 243 { 244 int err = 0; 245 246 mutex_lock(&cpu_add_remove_lock); 247 if (cpu_hotplug_disabled) 248 err = -EBUSY; 249 else 250 err = _cpu_up(cpu); 251 252 mutex_unlock(&cpu_add_remove_lock); 253 return err; 254 } 255 256 #ifdef CONFIG_SUSPEND_SMP 257 static cpumask_t frozen_cpus; 258 259 int disable_nonboot_cpus(void) 260 { 261 int cpu, first_cpu, error = 0; 262 263 mutex_lock(&cpu_add_remove_lock); 264 first_cpu = first_cpu(cpu_present_map); 265 if (!cpu_online(first_cpu)) { 266 error = _cpu_up(first_cpu); 267 if (error) { 268 printk(KERN_ERR "Could not bring CPU%d up.\n", 269 first_cpu); 270 goto out; 271 } 272 } 273 274 /* We take down all of the non-boot CPUs in one shot to avoid races 275 * with the userspace trying to use the CPU hotplug at the same time 276 */ 277 cpus_clear(frozen_cpus); 278 printk("Disabling non-boot CPUs ...\n"); 279 for_each_online_cpu(cpu) { 280 if (cpu == first_cpu) 281 continue; 282 error = _cpu_down(cpu); 283 if (!error) { 284 cpu_set(cpu, frozen_cpus); 285 printk("CPU%d is down\n", cpu); 286 } else { 287 printk(KERN_ERR "Error taking CPU%d down: %d\n", 288 cpu, error); 289 break; 290 } 291 } 292 if (!error) { 293 BUG_ON(num_online_cpus() > 1); 294 /* Make sure the CPUs won't be enabled by someone else */ 295 cpu_hotplug_disabled = 1; 296 } else { 297 printk(KERN_ERR "Non-boot CPUs are not disabled\n"); 298 } 299 out: 300 mutex_unlock(&cpu_add_remove_lock); 301 return error; 302 } 303 304 void enable_nonboot_cpus(void) 305 { 306 int cpu, error; 307 308 /* Allow everyone to use the CPU hotplug again */ 309 mutex_lock(&cpu_add_remove_lock); 310 cpu_hotplug_disabled = 0; 311 mutex_unlock(&cpu_add_remove_lock); 312 313 printk("Enabling non-boot CPUs ...\n"); 314 for_each_cpu_mask(cpu, frozen_cpus) { 315 error = cpu_up(cpu); 316 if (!error) { 317 printk("CPU%d is up\n", cpu); 318 continue; 319 } 320 printk(KERN_WARNING "Error taking CPU%d up: %d\n", 321 cpu, error); 322 } 323 cpus_clear(frozen_cpus); 324 } 325 #endif 326