[PATCH] cpu hotplug: make [un]register_cpu_notifier init time only
[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 <linux/mutex.h>
17
18 /* This protects CPUs going up and down... */
19 static DEFINE_MUTEX(cpucontrol);
20
21 static __cpuinitdata BLOCKING_NOTIFIER_HEAD(cpu_chain);
22
23 #ifdef CONFIG_HOTPLUG_CPU
24 static struct task_struct *lock_cpu_hotplug_owner;
25 static int lock_cpu_hotplug_depth;
26
27 static int __lock_cpu_hotplug(int interruptible)
28 {
29         int ret = 0;
30
31         if (lock_cpu_hotplug_owner != current) {
32                 if (interruptible)
33                         ret = mutex_lock_interruptible(&cpucontrol);
34                 else
35                         mutex_lock(&cpucontrol);
36         }
37
38         /*
39          * Set only if we succeed in locking
40          */
41         if (!ret) {
42                 lock_cpu_hotplug_depth++;
43                 lock_cpu_hotplug_owner = current;
44         }
45
46         return ret;
47 }
48
49 void lock_cpu_hotplug(void)
50 {
51         __lock_cpu_hotplug(0);
52 }
53 EXPORT_SYMBOL_GPL(lock_cpu_hotplug);
54
55 void unlock_cpu_hotplug(void)
56 {
57         if (--lock_cpu_hotplug_depth == 0) {
58                 lock_cpu_hotplug_owner = NULL;
59                 mutex_unlock(&cpucontrol);
60         }
61 }
62 EXPORT_SYMBOL_GPL(unlock_cpu_hotplug);
63
64 int lock_cpu_hotplug_interruptible(void)
65 {
66         return __lock_cpu_hotplug(1);
67 }
68 EXPORT_SYMBOL_GPL(lock_cpu_hotplug_interruptible);
69 #endif  /* CONFIG_HOTPLUG_CPU */
70
71 /* Need to know about CPUs going up/down? */
72 int __cpuinit register_cpu_notifier(struct notifier_block *nb)
73 {
74         return blocking_notifier_chain_register(&cpu_chain, nb);
75 }
76
77 #ifdef CONFIG_HOTPLUG_CPU
78
79 EXPORT_SYMBOL(register_cpu_notifier);
80
81 void unregister_cpu_notifier(struct notifier_block *nb)
82 {
83         blocking_notifier_chain_unregister(&cpu_chain, nb);
84 }
85 EXPORT_SYMBOL(unregister_cpu_notifier);
86
87 static inline void check_for_tasks(int cpu)
88 {
89         struct task_struct *p;
90
91         write_lock_irq(&tasklist_lock);
92         for_each_process(p) {
93                 if (task_cpu(p) == cpu &&
94                     (!cputime_eq(p->utime, cputime_zero) ||
95                      !cputime_eq(p->stime, cputime_zero)))
96                         printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
97                                 (state = %ld, flags = %lx) \n",
98                                  p->comm, p->pid, cpu, p->state, p->flags);
99         }
100         write_unlock_irq(&tasklist_lock);
101 }
102
103 /* Take this CPU down. */
104 static int take_cpu_down(void *unused)
105 {
106         int err;
107
108         /* Ensure this CPU doesn't handle any more interrupts. */
109         err = __cpu_disable();
110         if (err < 0)
111                 return err;
112
113         /* Force idle task to run as soon as we yield: it should
114            immediately notice cpu is offline and die quickly. */
115         sched_idle_next();
116         return 0;
117 }
118
119 int cpu_down(unsigned int cpu)
120 {
121         int err;
122         struct task_struct *p;
123         cpumask_t old_allowed, tmp;
124
125         if ((err = lock_cpu_hotplug_interruptible()) != 0)
126                 return err;
127
128         if (num_online_cpus() == 1) {
129                 err = -EBUSY;
130                 goto out;
131         }
132
133         if (!cpu_online(cpu)) {
134                 err = -EINVAL;
135                 goto out;
136         }
137
138         err = blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
139                                                 (void *)(long)cpu);
140         if (err == NOTIFY_BAD) {
141                 printk("%s: attempt to take down CPU %u failed\n",
142                                 __FUNCTION__, cpu);
143                 err = -EINVAL;
144                 goto out;
145         }
146
147         /* Ensure that we are not runnable on dying cpu */
148         old_allowed = current->cpus_allowed;
149         tmp = CPU_MASK_ALL;
150         cpu_clear(cpu, tmp);
151         set_cpus_allowed(current, tmp);
152
153         p = __stop_machine_run(take_cpu_down, NULL, cpu);
154         if (IS_ERR(p)) {
155                 /* CPU didn't die: tell everyone.  Can't complain. */
156                 if (blocking_notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
157                                 (void *)(long)cpu) == NOTIFY_BAD)
158                         BUG();
159
160                 err = PTR_ERR(p);
161                 goto out_allowed;
162         }
163
164         if (cpu_online(cpu))
165                 goto out_thread;
166
167         /* Wait for it to sleep (leaving idle task). */
168         while (!idle_cpu(cpu))
169                 yield();
170
171         /* This actually kills the CPU. */
172         __cpu_die(cpu);
173
174         /* Move it here so it can run. */
175         kthread_bind(p, get_cpu());
176         put_cpu();
177
178         /* CPU is completely dead: tell everyone.  Too late to complain. */
179         if (blocking_notifier_call_chain(&cpu_chain, CPU_DEAD,
180                         (void *)(long)cpu) == NOTIFY_BAD)
181                 BUG();
182
183         check_for_tasks(cpu);
184
185 out_thread:
186         err = kthread_stop(p);
187 out_allowed:
188         set_cpus_allowed(current, old_allowed);
189 out:
190         unlock_cpu_hotplug();
191         return err;
192 }
193 #endif /*CONFIG_HOTPLUG_CPU*/
194
195 int __devinit cpu_up(unsigned int cpu)
196 {
197         int ret;
198         void *hcpu = (void *)(long)cpu;
199
200         if ((ret = lock_cpu_hotplug_interruptible()) != 0)
201                 return ret;
202
203         if (cpu_online(cpu) || !cpu_present(cpu)) {
204                 ret = -EINVAL;
205                 goto out;
206         }
207
208         ret = blocking_notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
209         if (ret == NOTIFY_BAD) {
210                 printk("%s: attempt to bring up CPU %u failed\n",
211                                 __FUNCTION__, cpu);
212                 ret = -EINVAL;
213                 goto out_notify;
214         }
215
216         /* Arch-specific enabling code. */
217         ret = __cpu_up(cpu);
218         if (ret != 0)
219                 goto out_notify;
220         BUG_ON(!cpu_online(cpu));
221
222         /* Now call notifier in preparation. */
223         blocking_notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
224
225 out_notify:
226         if (ret != 0)
227                 blocking_notifier_call_chain(&cpu_chain,
228                                 CPU_UP_CANCELED, hcpu);
229 out:
230         unlock_cpu_hotplug();
231         return ret;
232 }