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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 BLOCKING_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 mutex_unlock(&cpu_bitmask_lock);
62 recursive = NULL;
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 return blocking_notifier_chain_register(&cpu_chain, nb);
72 }
73
74 #ifdef CONFIG_HOTPLUG_CPU
75
76 EXPORT_SYMBOL(register_cpu_notifier);
77
78 void unregister_cpu_notifier(struct notifier_block *nb)
79 {
80 blocking_notifier_chain_unregister(&cpu_chain, nb);
81 }
82 EXPORT_SYMBOL(unregister_cpu_notifier);
83
84 static inline void check_for_tasks(int cpu)
85 {
86 struct task_struct *p;
87
88 write_lock_irq(&tasklist_lock);
89 for_each_process(p) {
90 if (task_cpu(p) == cpu &&
91 (!cputime_eq(p->utime, cputime_zero) ||
92 !cputime_eq(p->stime, cputime_zero)))
93 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
94 (state = %ld, flags = %lx) \n",
95 p->comm, p->pid, cpu, p->state, p->flags);
96 }
97 write_unlock_irq(&tasklist_lock);
98 }
99
100 /* Take this CPU down. */
101 static int take_cpu_down(void *unused)
102 {
103 int err;
104
105 /* Ensure this CPU doesn't handle any more interrupts. */
106 err = __cpu_disable();
107 if (err < 0)
108 return err;
109
110 /* Force idle task to run as soon as we yield: it should
111 immediately notice cpu is offline and die quickly. */
112 sched_idle_next();
113 return 0;
114 }
115
116 /* Requires cpu_add_remove_lock to be held */
117 static int _cpu_down(unsigned int cpu)
118 {
119 int err;
120 struct task_struct *p;
121 cpumask_t old_allowed, tmp;
122
123 if (num_online_cpus() == 1)
124 return -EBUSY;
125
126 if (!cpu_online(cpu))
127 return -EINVAL;
128
129 err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
130 (void *)(long)cpu);
131 if (err == NOTIFY_BAD) {
132 printk("%s: attempt to take down CPU %u failed\n",
133 __FUNCTION__, cpu);
134 return -EINVAL;
135 }
136
137 /* Ensure that we are not runnable on dying cpu */
138 old_allowed = current->cpus_allowed;
139 tmp = CPU_MASK_ALL;
140 cpu_clear(cpu, tmp);
141 set_cpus_allowed(current, tmp);
142
143 mutex_lock(&cpu_bitmask_lock);
144 p = __stop_machine_run(take_cpu_down, NULL, cpu);
145 mutex_unlock(&cpu_bitmask_lock);
146
147 if (IS_ERR(p)) {
148 /* CPU didn't die: tell everyone. Can't complain. */
149 if (blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
150 (void *)(long)cpu) == NOTIFY_BAD)
151 BUG();
152
153 err = PTR_ERR(p);
154 goto out_allowed;
155 }
156
157 if (cpu_online(cpu))
158 goto out_thread;
159
160 /* Wait for it to sleep (leaving idle task). */
161 while (!idle_cpu(cpu))
162 yield();
163
164 /* This actually kills the CPU. */
165 __cpu_die(cpu);
166
167 /* Move it here so it can run. */
168 kthread_bind(p, get_cpu());
169 put_cpu();
170
171 /* CPU is completely dead: tell everyone. Too late to complain. */
172 if (blocking_notifier_call_chain(&cpu_chain, CPU_DEAD,
173 (void *)(long)cpu) == NOTIFY_BAD)
174 BUG();
175
176 check_for_tasks(cpu);
177
178 out_thread:
179 err = kthread_stop(p);
180 out_allowed:
181 set_cpus_allowed(current, old_allowed);
182 return err;
183 }
184
185 int cpu_down(unsigned int cpu)
186 {
187 int err = 0;
188
189 mutex_lock(&cpu_add_remove_lock);
190 if (cpu_hotplug_disabled)
191 err = -EBUSY;
192 else
193 err = _cpu_down(cpu);
194
195 mutex_unlock(&cpu_add_remove_lock);
196 return err;
197 }
198 #endif /*CONFIG_HOTPLUG_CPU*/
199
200 /* Requires cpu_add_remove_lock to be held */
201 static int __devinit _cpu_up(unsigned int cpu)
202 {
203 int ret;
204 void *hcpu = (void *)(long)cpu;
205
206 if (cpu_online(cpu) || !cpu_present(cpu))
207 return -EINVAL;
208
209 ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
210 if (ret == NOTIFY_BAD) {
211 printk("%s: attempt to bring up CPU %u failed\n",
212 __FUNCTION__, cpu);
213 ret = -EINVAL;
214 goto out_notify;
215 }
216
217 /* Arch-specific enabling code. */
218 mutex_lock(&cpu_bitmask_lock);
219 ret = __cpu_up(cpu);
220 mutex_unlock(&cpu_bitmask_lock);
221 if (ret != 0)
222 goto out_notify;
223 BUG_ON(!cpu_online(cpu));
224
225 /* Now call notifier in preparation. */
226 blocking_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
227
228 out_notify:
229 if (ret != 0)
230 blocking_notifier_call_chain(&cpu_chain,
231 CPU_UP_CANCELED, hcpu);
232
233 return ret;
234 }
235
236 int __devinit cpu_up(unsigned int cpu)
237 {
238 int err = 0;
239
240 mutex_lock(&cpu_add_remove_lock);
241 if (cpu_hotplug_disabled)
242 err = -EBUSY;
243 else
244 err = _cpu_up(cpu);
245
246 mutex_unlock(&cpu_add_remove_lock);
247 return err;
248 }
249
250 #ifdef CONFIG_SUSPEND_SMP
251 static cpumask_t frozen_cpus;
252
253 int disable_nonboot_cpus(void)
254 {
255 int cpu, first_cpu, error;
256
257 mutex_lock(&cpu_add_remove_lock);
258 first_cpu = first_cpu(cpu_present_map);
259 if (!cpu_online(first_cpu)) {
260 error = _cpu_up(first_cpu);
261 if (error) {
262 printk(KERN_ERR "Could not bring CPU%d up.\n",
263 first_cpu);
264 goto out;
265 }
266 }
267 error = set_cpus_allowed(current, cpumask_of_cpu(first_cpu));
268 if (error) {
269 printk(KERN_ERR "Could not run on CPU%d\n", first_cpu);
270 goto out;
271 }
272 /* We take down all of the non-boot CPUs in one shot to avoid races
273 * with the userspace trying to use the CPU hotplug at the same time
274 */
275 cpus_clear(frozen_cpus);
276 printk("Disabling non-boot CPUs ...\n");
277 for_each_online_cpu(cpu) {
278 if (cpu == first_cpu)
279 continue;
280 error = _cpu_down(cpu);
281 if (!error) {
282 cpu_set(cpu, frozen_cpus);
283 printk("CPU%d is down\n", cpu);
284 } else {
285 printk(KERN_ERR "Error taking CPU%d down: %d\n",
286 cpu, error);
287 break;
288 }
289 }
290 if (!error) {
291 BUG_ON(num_online_cpus() > 1);
292 /* Make sure the CPUs won't be enabled by someone else */
293 cpu_hotplug_disabled = 1;
294 } else {
295 printk(KERN_ERR "Non-boot CPUs are not disabled");
296 }
297 out:
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 mutex_unlock(&cpu_add_remove_lock);
310
311 printk("Enabling non-boot CPUs ...\n");
312 for_each_cpu_mask(cpu, frozen_cpus) {
313 error = cpu_up(cpu);
314 if (!error) {
315 printk("CPU%d is up\n", cpu);
316 continue;
317 }
318 printk(KERN_WARNING "Error taking CPU%d up: %d\n",
319 cpu, error);
320 }
321 cpus_clear(frozen_cpus);
322 }
323 #endif