[PATCH] create and destroy cpufreq sysfs entries based on cpu notifiers
[linux-2.6.git] / kernel / cpu.c
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 <asm/semaphore.h>
17
18 /* This protects CPUs going up and down... */
19 DECLARE_MUTEX(cpucontrol);
20 EXPORT_SYMBOL_GPL(cpucontrol);
21
22 static struct notifier_block *cpu_chain;
23
24 /* Need to know about CPUs going up/down? */
25 int register_cpu_notifier(struct notifier_block *nb)
26 {
27         int ret;
28
29         if ((ret = down_interruptible(&cpucontrol)) != 0)
30                 return ret;
31         ret = notifier_chain_register(&cpu_chain, nb);
32         up(&cpucontrol);
33         return ret;
34 }
35 EXPORT_SYMBOL(register_cpu_notifier);
36
37 void unregister_cpu_notifier(struct notifier_block *nb)
38 {
39         down(&cpucontrol);
40         notifier_chain_unregister(&cpu_chain, nb);
41         up(&cpucontrol);
42 }
43 EXPORT_SYMBOL(unregister_cpu_notifier);
44
45 #ifdef CONFIG_HOTPLUG_CPU
46 static inline void check_for_tasks(int cpu)
47 {
48         struct task_struct *p;
49
50         write_lock_irq(&tasklist_lock);
51         for_each_process(p) {
52                 if (task_cpu(p) == cpu &&
53                     (!cputime_eq(p->utime, cputime_zero) ||
54                      !cputime_eq(p->stime, cputime_zero)))
55                         printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
56                                 (state = %ld, flags = %lx) \n",
57                                  p->comm, p->pid, cpu, p->state, p->flags);
58         }
59         write_unlock_irq(&tasklist_lock);
60 }
61
62 /* Take this CPU down. */
63 static int take_cpu_down(void *unused)
64 {
65         int err;
66
67         /* Ensure this CPU doesn't handle any more interrupts. */
68         err = __cpu_disable();
69         if (err < 0)
70                 return err;
71
72         /* Force idle task to run as soon as we yield: it should
73            immediately notice cpu is offline and die quickly. */
74         sched_idle_next();
75         return 0;
76 }
77
78 int cpu_down(unsigned int cpu)
79 {
80         int err;
81         struct task_struct *p;
82         cpumask_t old_allowed, tmp;
83
84         if ((err = lock_cpu_hotplug_interruptible()) != 0)
85                 return err;
86
87         if (num_online_cpus() == 1) {
88                 err = -EBUSY;
89                 goto out;
90         }
91
92         if (!cpu_online(cpu)) {
93                 err = -EINVAL;
94                 goto out;
95         }
96
97         err = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
98                                                 (void *)(long)cpu);
99         if (err == NOTIFY_BAD) {
100                 printk("%s: attempt to take down CPU %u failed\n",
101                                 __FUNCTION__, cpu);
102                 err = -EINVAL;
103                 goto out;
104         }
105
106         /* Ensure that we are not runnable on dying cpu */
107         old_allowed = current->cpus_allowed;
108         tmp = CPU_MASK_ALL;
109         cpu_clear(cpu, tmp);
110         set_cpus_allowed(current, tmp);
111
112         p = __stop_machine_run(take_cpu_down, NULL, cpu);
113         if (IS_ERR(p)) {
114                 /* CPU didn't die: tell everyone.  Can't complain. */
115                 if (notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
116                                 (void *)(long)cpu) == NOTIFY_BAD)
117                         BUG();
118
119                 err = PTR_ERR(p);
120                 goto out_allowed;
121         }
122
123         if (cpu_online(cpu))
124                 goto out_thread;
125
126         /* Wait for it to sleep (leaving idle task). */
127         while (!idle_cpu(cpu))
128                 yield();
129
130         /* This actually kills the CPU. */
131         __cpu_die(cpu);
132
133         /* Move it here so it can run. */
134         kthread_bind(p, get_cpu());
135         put_cpu();
136
137         /* CPU is completely dead: tell everyone.  Too late to complain. */
138         if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu)
139             == NOTIFY_BAD)
140                 BUG();
141
142         check_for_tasks(cpu);
143
144 out_thread:
145         err = kthread_stop(p);
146 out_allowed:
147         set_cpus_allowed(current, old_allowed);
148 out:
149         unlock_cpu_hotplug();
150         return err;
151 }
152 #endif /*CONFIG_HOTPLUG_CPU*/
153
154 int __devinit cpu_up(unsigned int cpu)
155 {
156         int ret;
157         void *hcpu = (void *)(long)cpu;
158
159         if ((ret = down_interruptible(&cpucontrol)) != 0)
160                 return ret;
161
162         if (cpu_online(cpu) || !cpu_present(cpu)) {
163                 ret = -EINVAL;
164                 goto out;
165         }
166         ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
167         if (ret == NOTIFY_BAD) {
168                 printk("%s: attempt to bring up CPU %u failed\n",
169                                 __FUNCTION__, cpu);
170                 ret = -EINVAL;
171                 goto out_notify;
172         }
173
174         /* Arch-specific enabling code. */
175         ret = __cpu_up(cpu);
176         if (ret != 0)
177                 goto out_notify;
178         if (!cpu_online(cpu))
179                 BUG();
180
181         /* Now call notifier in preparation. */
182         notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
183
184 out_notify:
185         if (ret != 0)
186                 notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu);
187 out:
188         up(&cpucontrol);
189         return ret;
190 }