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