2 * Common SMP CPU bringup/teardown functions
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>
20 #ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
22 * For the hotplug case we keep the task structs around and reuse
25 static DEFINE_PER_CPU(struct task_struct *, idle_threads);
27 struct task_struct *idle_thread_get(unsigned int cpu)
29 struct task_struct *tsk = per_cpu(idle_threads, cpu);
32 return ERR_PTR(-ENOMEM);
37 void __init idle_thread_set_boot_cpu(void)
39 per_cpu(idle_threads, smp_processor_id()) = current;
43 * idle_init - Initialize the idle thread for a cpu
44 * @cpu: The cpu for which the idle thread should be initialized
46 * Creates the thread if it does not exist.
48 static inline void idle_init(unsigned int cpu)
50 struct task_struct *tsk = per_cpu(idle_threads, cpu);
55 pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
57 per_cpu(idle_threads, cpu) = tsk;
62 * idle_threads_init - Initialize idle threads for all cpus
64 void __init idle_threads_init(void)
66 unsigned int cpu, boot_cpu;
68 boot_cpu = smp_processor_id();
70 for_each_possible_cpu(cpu) {
77 #endif /* #ifdef CONFIG_SMP */
79 static LIST_HEAD(hotplug_threads);
80 static DEFINE_MUTEX(smpboot_threads_lock);
82 struct smpboot_thread_data {
85 struct smp_hotplug_thread *ht;
95 * smpboot_thread_fn - percpu hotplug thread loop function
96 * @data: thread data pointer
98 * Checks for thread stop and park conditions. Calls the necessary
99 * setup, cleanup, park and unpark functions for the registered
102 * Returns 1 when the thread should exit, 0 otherwise.
104 static int smpboot_thread_fn(void *data)
106 struct smpboot_thread_data *td = data;
107 struct smp_hotplug_thread *ht = td->ht;
110 set_current_state(TASK_INTERRUPTIBLE);
112 if (kthread_should_stop()) {
113 set_current_state(TASK_RUNNING);
116 ht->cleanup(td->cpu, cpu_online(td->cpu));
121 if (kthread_should_park()) {
122 __set_current_state(TASK_RUNNING);
124 if (ht->park && td->status == HP_THREAD_ACTIVE) {
125 BUG_ON(td->cpu != smp_processor_id());
127 td->status = HP_THREAD_PARKED;
130 /* We might have been woken for stop */
134 BUG_ON(td->cpu != smp_processor_id());
136 /* Check for state change setup */
137 switch (td->status) {
142 td->status = HP_THREAD_ACTIVE;
145 case HP_THREAD_PARKED:
149 td->status = HP_THREAD_ACTIVE;
154 if (!ht->thread_should_run(td->cpu)) {
158 set_current_state(TASK_RUNNING);
160 ht->thread_fn(td->cpu);
166 __smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
168 struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
169 struct smpboot_thread_data *td;
174 td = kzalloc_node(sizeof(*td), GFP_KERNEL, cpu_to_node(cpu));
180 tsk = kthread_create_on_cpu(smpboot_thread_fn, td, cpu,
186 get_task_struct(tsk);
187 *per_cpu_ptr(ht->store, cpu) = tsk;
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.
195 if (!wait_task_inactive(tsk, TASK_PARKED))
203 int smpboot_create_threads(unsigned int cpu)
205 struct smp_hotplug_thread *cur;
208 mutex_lock(&smpboot_threads_lock);
209 list_for_each_entry(cur, &hotplug_threads, list) {
210 ret = __smpboot_create_thread(cur, cpu);
214 mutex_unlock(&smpboot_threads_lock);
218 static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
220 struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
227 void smpboot_unpark_threads(unsigned int cpu)
229 struct smp_hotplug_thread *cur;
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);
237 static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
239 struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
241 if (tsk && !ht->selfparking)
245 void smpboot_park_threads(unsigned int cpu)
247 struct smp_hotplug_thread *cur;
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);
255 static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
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);
265 put_task_struct(tsk);
266 *per_cpu_ptr(ht->store, cpu) = NULL;
272 * smpboot_register_percpu_thread - Register a per_cpu thread related to hotplug
273 * @plug_thread: Hotplug thread descriptor
275 * Creates and starts the threads on all online cpus.
277 int smpboot_register_percpu_thread(struct smp_hotplug_thread *plug_thread)
282 mutex_lock(&smpboot_threads_lock);
283 for_each_online_cpu(cpu) {
284 ret = __smpboot_create_thread(plug_thread, cpu);
286 smpboot_destroy_threads(plug_thread);
289 smpboot_unpark_thread(plug_thread, cpu);
291 list_add(&plug_thread->list, &hotplug_threads);
293 mutex_unlock(&smpboot_threads_lock);
296 EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread);
299 * smpboot_unregister_percpu_thread - Unregister a per_cpu thread related to hotplug
300 * @plug_thread: Hotplug thread descriptor
302 * Stops all threads on all possible cpus.
304 void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
307 mutex_lock(&smpboot_threads_lock);
308 list_del(&plug_thread->list);
309 smpboot_destroy_threads(plug_thread);
310 mutex_unlock(&smpboot_threads_lock);
313 EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);