[PATCH] W1: Sync with w1/ds9490 tree.
[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
21 static struct notifier_block *cpu_chain;
22
23 /* Need to know about CPUs going up/down? */
24 int register_cpu_notifier(struct notifier_block *nb)
25 {
26         int ret;
27
28         if ((ret = down_interruptible(&cpucontrol)) != 0)
29                 return ret;
30         ret = notifier_chain_register(&cpu_chain, nb);
31         up(&cpucontrol);
32         return ret;
33 }
34 EXPORT_SYMBOL(register_cpu_notifier);
35
36 void unregister_cpu_notifier(struct notifier_block *nb)
37 {
38         down(&cpucontrol);
39         notifier_chain_unregister(&cpu_chain, nb);
40         up(&cpucontrol);
41 }
42 EXPORT_SYMBOL(unregister_cpu_notifier);
43
44 #ifdef CONFIG_HOTPLUG_CPU
45 static inline void check_for_tasks(int cpu)
46 {
47         struct task_struct *p;
48
49         write_lock_irq(&tasklist_lock);
50         for_each_process(p) {
51                 if (task_cpu(p) == cpu &&
52                     (!cputime_eq(p->utime, cputime_zero) ||
53                      !cputime_eq(p->stime, cputime_zero)))
54                         printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
55                                 (state = %ld, flags = %lx) \n",
56                                  p->comm, p->pid, cpu, p->state, p->flags);
57         }
58         write_unlock_irq(&tasklist_lock);
59 }
60
61 /* Take this CPU down. */
62 static int take_cpu_down(void *unused)
63 {
64         int err;
65
66         /* Ensure this CPU doesn't handle any more interrupts. */
67         err = __cpu_disable();
68         if (err < 0)
69                 return err;
70
71         /* Force idle task to run as soon as we yield: it should
72            immediately notice cpu is offline and die quickly. */
73         sched_idle_next();
74         return 0;
75 }
76
77 int cpu_down(unsigned int cpu)
78 {
79         int err;
80         struct task_struct *p;
81         cpumask_t old_allowed, tmp;
82
83         if ((err = lock_cpu_hotplug_interruptible()) != 0)
84                 return err;
85
86         if (num_online_cpus() == 1) {
87                 err = -EBUSY;
88                 goto out;
89         }
90
91         if (!cpu_online(cpu)) {
92                 err = -EINVAL;
93                 goto out;
94         }
95
96         err = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
97                                                 (void *)(long)cpu);
98         if (err == NOTIFY_BAD) {
99                 printk("%s: attempt to take down CPU %u failed\n",
100                                 __FUNCTION__, cpu);
101                 err = -EINVAL;
102                 goto out;
103         }
104
105         /* Ensure that we are not runnable on dying cpu */
106         old_allowed = current->cpus_allowed;
107         tmp = CPU_MASK_ALL;
108         cpu_clear(cpu, tmp);
109         set_cpus_allowed(current, tmp);
110
111         p = __stop_machine_run(take_cpu_down, NULL, cpu);
112         if (IS_ERR(p)) {
113                 /* CPU didn't die: tell everyone.  Can't complain. */
114                 if (notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
115                                 (void *)(long)cpu) == NOTIFY_BAD)
116                         BUG();
117
118                 err = PTR_ERR(p);
119                 goto out_allowed;
120         }
121
122         if (cpu_online(cpu))
123                 goto out_thread;
124
125         /* Wait for it to sleep (leaving idle task). */
126         while (!idle_cpu(cpu))
127                 yield();
128
129         /* This actually kills the CPU. */
130         __cpu_die(cpu);
131
132         /* Move it here so it can run. */
133         kthread_bind(p, get_cpu());
134         put_cpu();
135
136         /* CPU is completely dead: tell everyone.  Too late to complain. */
137         if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu)
138             == NOTIFY_BAD)
139                 BUG();
140
141         check_for_tasks(cpu);
142
143 out_thread:
144         err = kthread_stop(p);
145 out_allowed:
146         set_cpus_allowed(current, old_allowed);
147 out:
148         unlock_cpu_hotplug();
149         return err;
150 }
151 #endif /*CONFIG_HOTPLUG_CPU*/
152
153 int __devinit cpu_up(unsigned int cpu)
154 {
155         int ret;
156         void *hcpu = (void *)(long)cpu;
157
158         if ((ret = down_interruptible(&cpucontrol)) != 0)
159                 return ret;
160
161         if (cpu_online(cpu) || !cpu_present(cpu)) {
162                 ret = -EINVAL;
163                 goto out;
164         }
165         ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
166         if (ret == NOTIFY_BAD) {
167                 printk("%s: attempt to bring up CPU %u failed\n",
168                                 __FUNCTION__, cpu);
169                 ret = -EINVAL;
170                 goto out_notify;
171         }
172
173         /* Arch-specific enabling code. */
174         ret = __cpu_up(cpu);
175         if (ret != 0)
176                 goto out_notify;
177         if (!cpu_online(cpu))
178                 BUG();
179
180         /* Now call notifier in preparation. */
181         notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
182
183 out_notify:
184         if (ret != 0)
185                 notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu);
186 out:
187         up(&cpucontrol);
188         return ret;
189 }