BUG_ON() Conversion in kernel/cpu.c
[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 static DECLARE_MUTEX(cpucontrol);
20
21 static struct notifier_block *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 = down_interruptible(&cpucontrol);
34                 else
35                         down(&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                 up(&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 register_cpu_notifier(struct notifier_block *nb)
73 {
74         int ret;
75
76         if ((ret = lock_cpu_hotplug_interruptible()) != 0)
77                 return ret;
78         ret = notifier_chain_register(&cpu_chain, nb);
79         unlock_cpu_hotplug();
80         return ret;
81 }
82 EXPORT_SYMBOL(register_cpu_notifier);
83
84 void unregister_cpu_notifier(struct notifier_block *nb)
85 {
86         lock_cpu_hotplug();
87         notifier_chain_unregister(&cpu_chain, nb);
88         unlock_cpu_hotplug();
89 }
90 EXPORT_SYMBOL(unregister_cpu_notifier);
91
92 #ifdef CONFIG_HOTPLUG_CPU
93 static inline void check_for_tasks(int cpu)
94 {
95         struct task_struct *p;
96
97         write_lock_irq(&tasklist_lock);
98         for_each_process(p) {
99                 if (task_cpu(p) == cpu &&
100                     (!cputime_eq(p->utime, cputime_zero) ||
101                      !cputime_eq(p->stime, cputime_zero)))
102                         printk(KERN_WARNING "Task %s (pid = %d) is on cpu %d\
103                                 (state = %ld, flags = %lx) \n",
104                                  p->comm, p->pid, cpu, p->state, p->flags);
105         }
106         write_unlock_irq(&tasklist_lock);
107 }
108
109 /* Take this CPU down. */
110 static int take_cpu_down(void *unused)
111 {
112         int err;
113
114         /* Ensure this CPU doesn't handle any more interrupts. */
115         err = __cpu_disable();
116         if (err < 0)
117                 return err;
118
119         /* Force idle task to run as soon as we yield: it should
120            immediately notice cpu is offline and die quickly. */
121         sched_idle_next();
122         return 0;
123 }
124
125 int cpu_down(unsigned int cpu)
126 {
127         int err;
128         struct task_struct *p;
129         cpumask_t old_allowed, tmp;
130
131         if ((err = lock_cpu_hotplug_interruptible()) != 0)
132                 return err;
133
134         if (num_online_cpus() == 1) {
135                 err = -EBUSY;
136                 goto out;
137         }
138
139         if (!cpu_online(cpu)) {
140                 err = -EINVAL;
141                 goto out;
142         }
143
144         err = notifier_call_chain(&cpu_chain, CPU_DOWN_PREPARE,
145                                                 (void *)(long)cpu);
146         if (err == NOTIFY_BAD) {
147                 printk("%s: attempt to take down CPU %u failed\n",
148                                 __FUNCTION__, cpu);
149                 err = -EINVAL;
150                 goto out;
151         }
152
153         /* Ensure that we are not runnable on dying cpu */
154         old_allowed = current->cpus_allowed;
155         tmp = CPU_MASK_ALL;
156         cpu_clear(cpu, tmp);
157         set_cpus_allowed(current, tmp);
158
159         p = __stop_machine_run(take_cpu_down, NULL, cpu);
160         if (IS_ERR(p)) {
161                 /* CPU didn't die: tell everyone.  Can't complain. */
162                 if (notifier_call_chain(&cpu_chain, CPU_DOWN_FAILED,
163                                 (void *)(long)cpu) == NOTIFY_BAD)
164                         BUG();
165
166                 err = PTR_ERR(p);
167                 goto out_allowed;
168         }
169
170         if (cpu_online(cpu))
171                 goto out_thread;
172
173         /* Wait for it to sleep (leaving idle task). */
174         while (!idle_cpu(cpu))
175                 yield();
176
177         /* This actually kills the CPU. */
178         __cpu_die(cpu);
179
180         /* Move it here so it can run. */
181         kthread_bind(p, get_cpu());
182         put_cpu();
183
184         /* CPU is completely dead: tell everyone.  Too late to complain. */
185         if (notifier_call_chain(&cpu_chain, CPU_DEAD, (void *)(long)cpu)
186             == NOTIFY_BAD)
187                 BUG();
188
189         check_for_tasks(cpu);
190
191 out_thread:
192         err = kthread_stop(p);
193 out_allowed:
194         set_cpus_allowed(current, old_allowed);
195 out:
196         unlock_cpu_hotplug();
197         return err;
198 }
199 #endif /*CONFIG_HOTPLUG_CPU*/
200
201 int __devinit cpu_up(unsigned int cpu)
202 {
203         int ret;
204         void *hcpu = (void *)(long)cpu;
205
206         if ((ret = lock_cpu_hotplug_interruptible()) != 0)
207                 return ret;
208
209         if (cpu_online(cpu) || !cpu_present(cpu)) {
210                 ret = -EINVAL;
211                 goto out;
212         }
213
214         ret = notifier_call_chain(&cpu_chain, CPU_UP_PREPARE, hcpu);
215         if (ret == NOTIFY_BAD) {
216                 printk("%s: attempt to bring up CPU %u failed\n",
217                                 __FUNCTION__, cpu);
218                 ret = -EINVAL;
219                 goto out_notify;
220         }
221
222         /* Arch-specific enabling code. */
223         ret = __cpu_up(cpu);
224         if (ret != 0)
225                 goto out_notify;
226         BUG_ON(!cpu_online(cpu));
227
228         /* Now call notifier in preparation. */
229         notifier_call_chain(&cpu_chain, CPU_ONLINE, hcpu);
230
231 out_notify:
232         if (ret != 0)
233                 notifier_call_chain(&cpu_chain, CPU_UP_CANCELED, hcpu);
234 out:
235         unlock_cpu_hotplug();
236         return ret;
237 }