projects/linux·blob v2.6.18 · refs

225 lines · 4.9 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 BLOCKING_NOTIFIER_HEAD(cpu_chain);
23
24#ifdef CONFIG_HOTPLUG_CPU
25
26/* Crappy recursive lock-takers in cpufreq! Complain loudly about idiots */
27static struct task_struct *recursive;
28static int recursive_depth;
29
30void lock_cpu_hotplug(void)
31{
32 struct task_struct *tsk = current;
33
34 if (tsk == recursive) {
35 static int warnings = 10;
36 if (warnings) {
37 printk(KERN_ERR "Lukewarm IQ detected in hotplug locking\n");
38 WARN_ON(1);
39 warnings--;
40 }
41 recursive_depth++;
42 return;
43 }
44 mutex_lock(&cpu_bitmask_lock);
45 recursive = tsk;
46}
47EXPORT_SYMBOL_GPL(lock_cpu_hotplug);
48
49void unlock_cpu_hotplug(void)
50{
51 WARN_ON(recursive != current);
52 if (recursive_depth) {
53 recursive_depth--;
54 return;
55 }
56 mutex_unlock(&cpu_bitmask_lock);
57 recursive = NULL;
58}
59EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
60
61#endif /* CONFIG_HOTPLUG_CPU */
62
63/* Need to know about CPUs going up/down? */
64int __cpuinit register_cpu_notifier(struct notifier_block *nb)
65{
66 return blocking_notifier_chain_register(&cpu_chain, nb);
67}
68
69#ifdef CONFIG_HOTPLUG_CPU
70
71EXPORT_SYMBOL(register_cpu_notifier);
72
73void unregister_cpu_notifier(struct notifier_block *nb)
74{
75 blocking_notifier_chain_unregister(&cpu_chain, nb);
76}
77EXPORT_SYMBOL(unregister_cpu_notifier);
78
79static inline void check_for_tasks(int cpu)
80{
81 struct task_struct *p;
82
83 write_lock_irq(&tasklist_lock);
84 for_each_process(p) {
85 if (task_cpu(p) == cpu &&
86 (!cputime_eq(p->utime, cputime_zero) ||
87 !cputime_eq(p->stime, cputime_zero)))
88 printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
89 (state = %ld, flags = %lx) \n",
90 p->comm, p->pid, cpu, p->state, p->flags);
91 }
92 write_unlock_irq(&tasklist_lock);
93}
94
95/* Take this CPU down. */
96static int take_cpu_down(void *unused)
97{
98 int err;
99
100 /* Ensure this CPU doesn't handle any more interrupts. */
101 err = __cpu_disable();
102 if (err < 0)
103 return err;
104
105 /* Force idle task to run as soon as we yield: it should
106 immediately notice cpu is offline and die quickly. */
107 sched_idle_next();
108 return 0;
109}
110
111int cpu_down(unsigned int cpu)
112{
113 int err;
114 struct task_struct *p;
115 cpumask_t old_allowed, tmp;
116
117 mutex_lock(&cpu_add_remove_lock);
118 if (num_online_cpus() == 1) {
119 err = -EBUSY;
120 goto out;
121 }
122
123 if (!cpu_online(cpu)) {
124 err = -EINVAL;
125 goto out;
126 }
127
128 err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
129 (void *)(long)cpu);
130 if (err == NOTIFY_BAD) {
131 printk("%s: attempt to take down CPU %u failed\n",
132 __FUNCTION__, cpu);
133 err = -EINVAL;
134 goto out;
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
178out_thread:
179 err = kthread_stop(p);
180out_allowed:
181 set_cpus_allowed(current, old_allowed);
182out:
183 mutex_unlock(&cpu_add_remove_lock);
184 return err;
185}
186#endif /*CONFIG_HOTPLUG_CPU*/
187
188int __devinit cpu_up(unsigned int cpu)
189{
190 int ret;
191 void *hcpu = (void *)(long)cpu;
192
193 mutex_lock(&cpu_add_remove_lock);
194 if (cpu_online(cpu) || !cpu_present(cpu)) {
195 ret = -EINVAL;
196 goto out;
197 }
198
199 ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
200 if (ret == NOTIFY_BAD) {
201 printk("%s: attempt to bring up CPU %u failed\n",
202 __FUNCTION__, cpu);
203 ret = -EINVAL;
204 goto out_notify;
205 }
206
207 /* Arch-specific enabling code. */
208 mutex_lock(&cpu_bitmask_lock);
209 ret = __cpu_up(cpu);
210 mutex_unlock(&cpu_bitmask_lock);
211 if (ret != 0)
212 goto out_notify;
213 BUG_ON(!cpu_online(cpu));
214
215 /* Now call notifier in preparation. */
216 blocking_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
217
218out_notify:
219 if (ret != 0)
220 blocking_notifier_call_chain(&cpu_chain,
221 CPU_UP_CANCELED, hcpu);
222out:
223 mutex_unlock(&cpu_add_remove_lock);
224 return ret;
225}