projects/linux·blob v3.10-rc6 · refs

313 lines · 6.9 KiB

1/*
2 * Common SMP CPU bringup/teardown functions
3 */
4#include <linux/cpu.h>
5#include <linux/err.h>
6#include <linux/smp.h>
7#include <linux/init.h>
8#include <linux/list.h>
9#include <linux/slab.h>
10#include <linux/sched.h>
11#include <linux/export.h>
12#include <linux/percpu.h>
13#include <linux/kthread.h>
14#include <linux/smpboot.h>
15
16#include "smpboot.h"
17
18#ifdef CONFIG_SMP
19
20#ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
21/*
22 * For the hotplug case we keep the task structs around and reuse
23 * them.
24 */
25static DEFINE_PER_CPU(struct task_struct *, idle_threads);
26
27struct task_struct * __cpuinit idle_thread_get(unsigned int cpu)
28{
29 struct task_struct *tsk = per_cpu(idle_threads, cpu);
30
31 if (!tsk)
32 return ERR_PTR(-ENOMEM);
33 init_idle(tsk, cpu);
34 return tsk;
35}
36
37void __init idle_thread_set_boot_cpu(void)
38{
39 per_cpu(idle_threads, smp_processor_id()) = current;
40}
41
42/**
43 * idle_init - Initialize the idle thread for a cpu
44 * @cpu: The cpu for which the idle thread should be initialized
45 *
46 * Creates the thread if it does not exist.
47 */
48static inline void idle_init(unsigned int cpu)
49{
50 struct task_struct *tsk = per_cpu(idle_threads, cpu);
51
52 if (!tsk) {
53 tsk = fork_idle(cpu);
54 if (IS_ERR(tsk))
55 pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
56 else
57 per_cpu(idle_threads, cpu) = tsk;
58 }
59}
60
61/**
62 * idle_threads_init - Initialize idle threads for all cpus
63 */
64void __init idle_threads_init(void)
65{
66 unsigned int cpu, boot_cpu;
67
68 boot_cpu = smp_processor_id();
69
70 for_each_possible_cpu(cpu) {
71 if (cpu != boot_cpu)
72 idle_init(cpu);
73 }
74}
75#endif
76
77#endif /* #ifdef CONFIG_SMP */
78
79static LIST_HEAD(hotplug_threads);
80static DEFINE_MUTEX(smpboot_threads_lock);
81
82struct smpboot_thread_data {
83 unsigned int cpu;
84 unsigned int status;
85 struct smp_hotplug_thread *ht;
86};
87
88enum {
89 HP_THREAD_NONE = 0,
90 HP_THREAD_ACTIVE,
91 HP_THREAD_PARKED,
92};
93
94/**
95 * smpboot_thread_fn - percpu hotplug thread loop function
96 * @data: thread data pointer
97 *
98 * Checks for thread stop and park conditions. Calls the necessary
99 * setup, cleanup, park and unpark functions for the registered
100 * thread.
101 *
102 * Returns 1 when the thread should exit, 0 otherwise.
103 */
104static int smpboot_thread_fn(void *data)
105{
106 struct smpboot_thread_data *td = data;
107 struct smp_hotplug_thread *ht = td->ht;
108
109 while (1) {
110 set_current_state(TASK_INTERRUPTIBLE);
111 preempt_disable();
112 if (kthread_should_stop()) {
113 set_current_state(TASK_RUNNING);
114 preempt_enable();
115 if (ht->cleanup)
116 ht->cleanup(td->cpu, cpu_online(td->cpu));
117 kfree(td);
118 return 0;
119 }
120
121 if (kthread_should_park()) {
122 __set_current_state(TASK_RUNNING);
123 preempt_enable();
124 if (ht->park && td->status == HP_THREAD_ACTIVE) {
125 BUG_ON(td->cpu != smp_processor_id());
126 ht->park(td->cpu);
127 td->status = HP_THREAD_PARKED;
128 }
129 kthread_parkme();
130 /* We might have been woken for stop */
131 continue;
132 }
133
134 BUG_ON(td->cpu != smp_processor_id());
135
136 /* Check for state change setup */
137 switch (td->status) {
138 case HP_THREAD_NONE:
139 preempt_enable();
140 if (ht->setup)
141 ht->setup(td->cpu);
142 td->status = HP_THREAD_ACTIVE;
143 preempt_disable();
144 break;
145 case HP_THREAD_PARKED:
146 preempt_enable();
147 if (ht->unpark)
148 ht->unpark(td->cpu);
149 td->status = HP_THREAD_ACTIVE;
150 preempt_disable();
151 break;
152 }
153
154 if (!ht->thread_should_run(td->cpu)) {
155 preempt_enable();
156 schedule();
157 } else {
158 set_current_state(TASK_RUNNING);
159 preempt_enable();
160 ht->thread_fn(td->cpu);
161 }
162 }
163}
164
165static int
166__smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
167{
168 struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
169 struct smpboot_thread_data *td;
170
171 if (tsk)
172 return 0;
173
174 td = kzalloc_node(sizeof(*td), GFP_KERNEL, cpu_to_node(cpu));
175 if (!td)
176 return -ENOMEM;
177 td->cpu = cpu;
178 td->ht = ht;
179
180 tsk = kthread_create_on_cpu(smpboot_thread_fn, td, cpu,
181 ht->thread_comm);
182 if (IS_ERR(tsk)) {
183 kfree(td);
184 return PTR_ERR(tsk);
185 }
186 get_task_struct(tsk);
187 *per_cpu_ptr(ht->store, cpu) = tsk;
188 if (ht->create) {
189 /*
190 * Make sure that the task has actually scheduled out
191 * into park position, before calling the create
192 * callback. At least the migration thread callback
193 * requires that the task is off the runqueue.
194 */
195 if (!wait_task_inactive(tsk, TASK_PARKED))
196 WARN_ON(1);
197 else
198 ht->create(cpu);
199 }
200 return 0;
201}
202
203int smpboot_create_threads(unsigned int cpu)
204{
205 struct smp_hotplug_thread *cur;
206 int ret = 0;
207
208 mutex_lock(&smpboot_threads_lock);
209 list_for_each_entry(cur, &hotplug_threads, list) {
210 ret = __smpboot_create_thread(cur, cpu);
211 if (ret)
212 break;
213 }
214 mutex_unlock(&smpboot_threads_lock);
215 return ret;
216}
217
218static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
219{
220 struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
221
222 if (ht->pre_unpark)
223 ht->pre_unpark(cpu);
224 kthread_unpark(tsk);
225}
226
227void smpboot_unpark_threads(unsigned int cpu)
228{
229 struct smp_hotplug_thread *cur;
230
231 mutex_lock(&smpboot_threads_lock);
232 list_for_each_entry(cur, &hotplug_threads, list)
233 smpboot_unpark_thread(cur, cpu);
234 mutex_unlock(&smpboot_threads_lock);
235}
236
237static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
238{
239 struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
240
241 if (tsk && !ht->selfparking)
242 kthread_park(tsk);
243}
244
245void smpboot_park_threads(unsigned int cpu)
246{
247 struct smp_hotplug_thread *cur;
248
249 mutex_lock(&smpboot_threads_lock);
250 list_for_each_entry_reverse(cur, &hotplug_threads, list)
251 smpboot_park_thread(cur, cpu);
252 mutex_unlock(&smpboot_threads_lock);
253}
254
255static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
256{
257 unsigned int cpu;
258
259 /* We need to destroy also the parked threads of offline cpus */
260 for_each_possible_cpu(cpu) {
261 struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
262
263 if (tsk) {
264 kthread_stop(tsk);
265 put_task_struct(tsk);
266 *per_cpu_ptr(ht->store, cpu) = NULL;
267 }
268 }
269}
270
271/**
272 * smpboot_register_percpu_thread - Register a per_cpu thread related to hotplug
273 * @plug_thread: Hotplug thread descriptor
274 *
275 * Creates and starts the threads on all online cpus.
276 */
277int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread)
278{
279 unsigned int cpu;
280 int ret = 0;
281
282 mutex_lock(&smpboot_threads_lock);
283 for_each_online_cpu(cpu) {
284 ret = __smpboot_create_thread(plug_thread, cpu);
285 if (ret) {
286 smpboot_destroy_threads(plug_thread);
287 goto out;
288 }
289 smpboot_unpark_thread(plug_thread, cpu);
290 }
291 list_add(&plug_thread->list, &hotplug_threads);
292out:
293 mutex_unlock(&smpboot_threads_lock);
294 return ret;
295}
296EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread);
297
298/**
299 * smpboot_unregister_percpu_thread - Unregister a per_cpu thread related to hotplug
300 * @plug_thread: Hotplug thread descriptor
301 *
302 * Stops all threads on all possible cpus.
303 */
304void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
305{
306 get_online_cpus();
307 mutex_lock(&smpboot_threads_lock);
308 list_del(&plug_thread->list);
309 smpboot_destroy_threads(plug_thread);
310 mutex_unlock(&smpboot_threads_lock);
311 put_online_cpus();
312}
313EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);