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