projects/linux·blob v2.6.24-rc1 · refs

349 lines · 8.2 KiB

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... */
19static DEFINE_MUTEX(cpu_add_remove_lock);
20static DEFINE_MUTEX(cpu_bitmask_lock);
21
22static __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 */
27static int cpu_hotplug_disabled;
28
29#ifdef CONFIG_HOTPLUG_CPU
30
31/* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */
32static struct task_struct *recursive;
33static int recursive_depth;
34
35void 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}
52EXPORT_SYMBOL_GPL(lock_cpu_hotplug);
53
54void 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}
64EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
65
66#endif /* CONFIG_HOTPLUG_CPU */
67
68/* Need to know about CPUs going up/down? */
69int __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
80EXPORT_SYMBOL(register_cpu_notifier);
81
82void 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}
88EXPORT_SYMBOL(unregister_cpu_notifier);
89
90static 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
107struct take_cpu_down_param {
108 unsigned long mod;
109 void *hcpu;
110};
111
112/* Take this CPU down. */
113static 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 */
132static 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
200out_thread:
201 err = kthread_stop(p);
202out_allowed:
203 set_cpus_allowed(current, old_allowed);
204out_release:
205 raw_notifier_call_chain(&cpu_chain, CPU_LOCK_RELEASE, hcpu);
206 return err;
207}
208
209int 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 */
225static 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
256out_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
265int __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
289static cpumask_t frozen_cpus;
290
291int 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
326void 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);
346out:
347 mutex_unlock(&cpu_add_remove_lock);
348}
349#endif /* CONFIG_PM_SLEEP_SMP */