Revert "FROMLIST: arm64: Introduce uaccess_{disable,enable} functionality based on...
[firefly-linux-kernel-4.4.55.git] / kernel / smpboot.c
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/delay.h>
8 #include <linux/init.h>
9 #include <linux/list.h>
10 #include <linux/slab.h>
11 #include <linux/sched.h>
12 #include <linux/export.h>
13 #include <linux/percpu.h>
14 #include <linux/kthread.h>
15 #include <linux/smpboot.h>
16
17 #include "smpboot.h"
18
19 #ifdef CONFIG_SMP
20
21 #ifdef CONFIG_GENERIC_SMP_IDLE_THREAD
22 /*
23  * For the hotplug case we keep the task structs around and reuse
24  * them.
25  */
26 static DEFINE_PER_CPU(struct task_struct *, idle_threads);
27
28 struct task_struct *idle_thread_get(unsigned int cpu)
29 {
30         struct task_struct *tsk = per_cpu(idle_threads, cpu);
31
32         if (!tsk)
33                 return ERR_PTR(-ENOMEM);
34         init_idle(tsk, cpu);
35         return tsk;
36 }
37
38 void __init idle_thread_set_boot_cpu(void)
39 {
40         per_cpu(idle_threads, smp_processor_id()) = current;
41 }
42
43 /**
44  * idle_init - Initialize the idle thread for a cpu
45  * @cpu:        The cpu for which the idle thread should be initialized
46  *
47  * Creates the thread if it does not exist.
48  */
49 static inline void idle_init(unsigned int cpu)
50 {
51         struct task_struct *tsk = per_cpu(idle_threads, cpu);
52
53         if (!tsk) {
54                 tsk = fork_idle(cpu);
55                 if (IS_ERR(tsk))
56                         pr_err("SMP: fork_idle() failed for CPU %u\n", cpu);
57                 else
58                         per_cpu(idle_threads, cpu) = tsk;
59         }
60 }
61
62 /**
63  * idle_threads_init - Initialize idle threads for all cpus
64  */
65 void __init idle_threads_init(void)
66 {
67         unsigned int cpu, boot_cpu;
68
69         boot_cpu = smp_processor_id();
70
71         for_each_possible_cpu(cpu) {
72                 if (cpu != boot_cpu)
73                         idle_init(cpu);
74         }
75 }
76 #endif
77
78 #endif /* #ifdef CONFIG_SMP */
79
80 static LIST_HEAD(hotplug_threads);
81 static DEFINE_MUTEX(smpboot_threads_lock);
82
83 struct smpboot_thread_data {
84         unsigned int                    cpu;
85         unsigned int                    status;
86         struct smp_hotplug_thread       *ht;
87 };
88
89 enum {
90         HP_THREAD_NONE = 0,
91         HP_THREAD_ACTIVE,
92         HP_THREAD_PARKED,
93 };
94
95 /**
96  * smpboot_thread_fn - percpu hotplug thread loop function
97  * @data:       thread data pointer
98  *
99  * Checks for thread stop and park conditions. Calls the necessary
100  * setup, cleanup, park and unpark functions for the registered
101  * thread.
102  *
103  * Returns 1 when the thread should exit, 0 otherwise.
104  */
105 static int smpboot_thread_fn(void *data)
106 {
107         struct smpboot_thread_data *td = data;
108         struct smp_hotplug_thread *ht = td->ht;
109
110         while (1) {
111                 set_current_state(TASK_INTERRUPTIBLE);
112                 preempt_disable();
113                 if (kthread_should_stop()) {
114                         __set_current_state(TASK_RUNNING);
115                         preempt_enable();
116                         /* cleanup must mirror setup */
117                         if (ht->cleanup && td->status != HP_THREAD_NONE)
118                                 ht->cleanup(td->cpu, cpu_online(td->cpu));
119                         kfree(td);
120                         return 0;
121                 }
122
123                 if (kthread_should_park()) {
124                         __set_current_state(TASK_RUNNING);
125                         preempt_enable();
126                         if (ht->park && td->status == HP_THREAD_ACTIVE) {
127                                 BUG_ON(td->cpu != smp_processor_id());
128                                 ht->park(td->cpu);
129                                 td->status = HP_THREAD_PARKED;
130                         }
131                         kthread_parkme();
132                         /* We might have been woken for stop */
133                         continue;
134                 }
135
136                 BUG_ON(td->cpu != smp_processor_id());
137
138                 /* Check for state change setup */
139                 switch (td->status) {
140                 case HP_THREAD_NONE:
141                         __set_current_state(TASK_RUNNING);
142                         preempt_enable();
143                         if (ht->setup)
144                                 ht->setup(td->cpu);
145                         td->status = HP_THREAD_ACTIVE;
146                         continue;
147
148                 case HP_THREAD_PARKED:
149                         __set_current_state(TASK_RUNNING);
150                         preempt_enable();
151                         if (ht->unpark)
152                                 ht->unpark(td->cpu);
153                         td->status = HP_THREAD_ACTIVE;
154                         continue;
155                 }
156
157                 if (!ht->thread_should_run(td->cpu)) {
158                         preempt_enable_no_resched();
159                         schedule();
160                 } else {
161                         __set_current_state(TASK_RUNNING);
162                         preempt_enable();
163                         ht->thread_fn(td->cpu);
164                 }
165         }
166 }
167
168 static int
169 __smpboot_create_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
170 {
171         struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
172         struct smpboot_thread_data *td;
173
174         if (tsk)
175                 return 0;
176
177         td = kzalloc_node(sizeof(*td), GFP_KERNEL, cpu_to_node(cpu));
178         if (!td)
179                 return -ENOMEM;
180         td->cpu = cpu;
181         td->ht = ht;
182
183         tsk = kthread_create_on_cpu(smpboot_thread_fn, td, cpu,
184                                     ht->thread_comm);
185         if (IS_ERR(tsk)) {
186                 kfree(td);
187                 return PTR_ERR(tsk);
188         }
189         get_task_struct(tsk);
190         *per_cpu_ptr(ht->store, cpu) = tsk;
191         if (ht->create) {
192                 /*
193                  * Make sure that the task has actually scheduled out
194                  * into park position, before calling the create
195                  * callback. At least the migration thread callback
196                  * requires that the task is off the runqueue.
197                  */
198                 if (!wait_task_inactive(tsk, TASK_PARKED))
199                         WARN_ON(1);
200                 else
201                         ht->create(cpu);
202         }
203         return 0;
204 }
205
206 int smpboot_create_threads(unsigned int cpu)
207 {
208         struct smp_hotplug_thread *cur;
209         int ret = 0;
210
211         mutex_lock(&smpboot_threads_lock);
212         list_for_each_entry(cur, &hotplug_threads, list) {
213                 ret = __smpboot_create_thread(cur, cpu);
214                 if (ret)
215                         break;
216         }
217         mutex_unlock(&smpboot_threads_lock);
218         return ret;
219 }
220
221 static void smpboot_unpark_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
222 {
223         struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
224
225         if (!ht->selfparking)
226                 kthread_unpark(tsk);
227 }
228
229 void smpboot_unpark_threads(unsigned int cpu)
230 {
231         struct smp_hotplug_thread *cur;
232
233         mutex_lock(&smpboot_threads_lock);
234         list_for_each_entry(cur, &hotplug_threads, list)
235                 if (cpumask_test_cpu(cpu, cur->cpumask))
236                         smpboot_unpark_thread(cur, cpu);
237         mutex_unlock(&smpboot_threads_lock);
238 }
239
240 static void smpboot_park_thread(struct smp_hotplug_thread *ht, unsigned int cpu)
241 {
242         struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
243
244         if (tsk && !ht->selfparking)
245                 kthread_park(tsk);
246 }
247
248 void smpboot_park_threads(unsigned int cpu)
249 {
250         struct smp_hotplug_thread *cur;
251
252         mutex_lock(&smpboot_threads_lock);
253         list_for_each_entry_reverse(cur, &hotplug_threads, list)
254                 smpboot_park_thread(cur, cpu);
255         mutex_unlock(&smpboot_threads_lock);
256 }
257
258 static void smpboot_destroy_threads(struct smp_hotplug_thread *ht)
259 {
260         unsigned int cpu;
261
262         /* We need to destroy also the parked threads of offline cpus */
263         for_each_possible_cpu(cpu) {
264                 struct task_struct *tsk = *per_cpu_ptr(ht->store, cpu);
265
266                 if (tsk) {
267                         kthread_stop(tsk);
268                         put_task_struct(tsk);
269                         *per_cpu_ptr(ht->store, cpu) = NULL;
270                 }
271         }
272 }
273
274 /**
275  * smpboot_register_percpu_thread_cpumask - Register a per_cpu thread related
276  *                                          to hotplug
277  * @plug_thread:        Hotplug thread descriptor
278  * @cpumask:            The cpumask where threads run
279  *
280  * Creates and starts the threads on all online cpus.
281  */
282 int smpboot_register_percpu_thread_cpumask(struct smp_hotplug_thread *plug_thread,
283                                            const struct cpumask *cpumask)
284 {
285         unsigned int cpu;
286         int ret = 0;
287
288         if (!alloc_cpumask_var(&plug_thread->cpumask, GFP_KERNEL))
289                 return -ENOMEM;
290         cpumask_copy(plug_thread->cpumask, cpumask);
291
292         get_online_cpus();
293         mutex_lock(&smpboot_threads_lock);
294         for_each_online_cpu(cpu) {
295                 ret = __smpboot_create_thread(plug_thread, cpu);
296                 if (ret) {
297                         smpboot_destroy_threads(plug_thread);
298                         free_cpumask_var(plug_thread->cpumask);
299                         goto out;
300                 }
301                 if (cpumask_test_cpu(cpu, cpumask))
302                         smpboot_unpark_thread(plug_thread, cpu);
303         }
304         list_add(&plug_thread->list, &hotplug_threads);
305 out:
306         mutex_unlock(&smpboot_threads_lock);
307         put_online_cpus();
308         return ret;
309 }
310 EXPORT_SYMBOL_GPL(smpboot_register_percpu_thread_cpumask);
311
312 /**
313  * smpboot_unregister_percpu_thread - Unregister a per_cpu thread related to hotplug
314  * @plug_thread:        Hotplug thread descriptor
315  *
316  * Stops all threads on all possible cpus.
317  */
318 void smpboot_unregister_percpu_thread(struct smp_hotplug_thread *plug_thread)
319 {
320         get_online_cpus();
321         mutex_lock(&smpboot_threads_lock);
322         list_del(&plug_thread->list);
323         smpboot_destroy_threads(plug_thread);
324         mutex_unlock(&smpboot_threads_lock);
325         put_online_cpus();
326         free_cpumask_var(plug_thread->cpumask);
327 }
328 EXPORT_SYMBOL_GPL(smpboot_unregister_percpu_thread);
329
330 /**
331  * smpboot_update_cpumask_percpu_thread - Adjust which per_cpu hotplug threads stay parked
332  * @plug_thread:        Hotplug thread descriptor
333  * @new:                Revised mask to use
334  *
335  * The cpumask field in the smp_hotplug_thread must not be updated directly
336  * by the client, but only by calling this function.
337  * This function can only be called on a registered smp_hotplug_thread.
338  */
339 int smpboot_update_cpumask_percpu_thread(struct smp_hotplug_thread *plug_thread,
340                                          const struct cpumask *new)
341 {
342         struct cpumask *old = plug_thread->cpumask;
343         cpumask_var_t tmp;
344         unsigned int cpu;
345
346         if (!alloc_cpumask_var(&tmp, GFP_KERNEL))
347                 return -ENOMEM;
348
349         get_online_cpus();
350         mutex_lock(&smpboot_threads_lock);
351
352         /* Park threads that were exclusively enabled on the old mask. */
353         cpumask_andnot(tmp, old, new);
354         for_each_cpu_and(cpu, tmp, cpu_online_mask)
355                 smpboot_park_thread(plug_thread, cpu);
356
357         /* Unpark threads that are exclusively enabled on the new mask. */
358         cpumask_andnot(tmp, new, old);
359         for_each_cpu_and(cpu, tmp, cpu_online_mask)
360                 smpboot_unpark_thread(plug_thread, cpu);
361
362         cpumask_copy(old, new);
363
364         mutex_unlock(&smpboot_threads_lock);
365         put_online_cpus();
366
367         free_cpumask_var(tmp);
368
369         return 0;
370 }
371 EXPORT_SYMBOL_GPL(smpboot_update_cpumask_percpu_thread);
372
373 static DEFINE_PER_CPU(atomic_t, cpu_hotplug_state) = ATOMIC_INIT(CPU_POST_DEAD);
374
375 /*
376  * Called to poll specified CPU's state, for example, when waiting for
377  * a CPU to come online.
378  */
379 int cpu_report_state(int cpu)
380 {
381         return atomic_read(&per_cpu(cpu_hotplug_state, cpu));
382 }
383
384 /*
385  * If CPU has died properly, set its state to CPU_UP_PREPARE and
386  * return success.  Otherwise, return -EBUSY if the CPU died after
387  * cpu_wait_death() timed out.  And yet otherwise again, return -EAGAIN
388  * if cpu_wait_death() timed out and the CPU still hasn't gotten around
389  * to dying.  In the latter two cases, the CPU might not be set up
390  * properly, but it is up to the arch-specific code to decide.
391  * Finally, -EIO indicates an unanticipated problem.
392  *
393  * Note that it is permissible to omit this call entirely, as is
394  * done in architectures that do no CPU-hotplug error checking.
395  */
396 int cpu_check_up_prepare(int cpu)
397 {
398         if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) {
399                 atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
400                 return 0;
401         }
402
403         switch (atomic_read(&per_cpu(cpu_hotplug_state, cpu))) {
404
405         case CPU_POST_DEAD:
406
407                 /* The CPU died properly, so just start it up again. */
408                 atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_UP_PREPARE);
409                 return 0;
410
411         case CPU_DEAD_FROZEN:
412
413                 /*
414                  * Timeout during CPU death, so let caller know.
415                  * The outgoing CPU completed its processing, but after
416                  * cpu_wait_death() timed out and reported the error. The
417                  * caller is free to proceed, in which case the state
418                  * will be reset properly by cpu_set_state_online().
419                  * Proceeding despite this -EBUSY return makes sense
420                  * for systems where the outgoing CPUs take themselves
421                  * offline, with no post-death manipulation required from
422                  * a surviving CPU.
423                  */
424                 return -EBUSY;
425
426         case CPU_BROKEN:
427
428                 /*
429                  * The most likely reason we got here is that there was
430                  * a timeout during CPU death, and the outgoing CPU never
431                  * did complete its processing.  This could happen on
432                  * a virtualized system if the outgoing VCPU gets preempted
433                  * for more than five seconds, and the user attempts to
434                  * immediately online that same CPU.  Trying again later
435                  * might return -EBUSY above, hence -EAGAIN.
436                  */
437                 return -EAGAIN;
438
439         default:
440
441                 /* Should not happen.  Famous last words. */
442                 return -EIO;
443         }
444 }
445
446 /*
447  * Mark the specified CPU online.
448  *
449  * Note that it is permissible to omit this call entirely, as is
450  * done in architectures that do no CPU-hotplug error checking.
451  */
452 void cpu_set_state_online(int cpu)
453 {
454         (void)atomic_xchg(&per_cpu(cpu_hotplug_state, cpu), CPU_ONLINE);
455 }
456
457 #ifdef CONFIG_HOTPLUG_CPU
458
459 /*
460  * Wait for the specified CPU to exit the idle loop and die.
461  */
462 bool cpu_wait_death(unsigned int cpu, int seconds)
463 {
464         int jf_left = seconds * HZ;
465         int oldstate;
466         bool ret = true;
467         int sleep_jf = 1;
468
469         might_sleep();
470
471         /* The outgoing CPU will normally get done quite quickly. */
472         if (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) == CPU_DEAD)
473                 goto update_state;
474         udelay(5);
475
476         /* But if the outgoing CPU dawdles, wait increasingly long times. */
477         while (atomic_read(&per_cpu(cpu_hotplug_state, cpu)) != CPU_DEAD) {
478                 schedule_timeout_uninterruptible(sleep_jf);
479                 jf_left -= sleep_jf;
480                 if (jf_left <= 0)
481                         break;
482                 sleep_jf = DIV_ROUND_UP(sleep_jf * 11, 10);
483         }
484 update_state:
485         oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
486         if (oldstate == CPU_DEAD) {
487                 /* Outgoing CPU died normally, update state. */
488                 smp_mb(); /* atomic_read() before update. */
489                 atomic_set(&per_cpu(cpu_hotplug_state, cpu), CPU_POST_DEAD);
490         } else {
491                 /* Outgoing CPU still hasn't died, set state accordingly. */
492                 if (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
493                                    oldstate, CPU_BROKEN) != oldstate)
494                         goto update_state;
495                 ret = false;
496         }
497         return ret;
498 }
499
500 /*
501  * Called by the outgoing CPU to report its successful death.  Return
502  * false if this report follows the surviving CPU's timing out.
503  *
504  * A separate "CPU_DEAD_FROZEN" is used when the surviving CPU
505  * timed out.  This approach allows architectures to omit calls to
506  * cpu_check_up_prepare() and cpu_set_state_online() without defeating
507  * the next cpu_wait_death()'s polling loop.
508  */
509 bool cpu_report_death(void)
510 {
511         int oldstate;
512         int newstate;
513         int cpu = smp_processor_id();
514
515         do {
516                 oldstate = atomic_read(&per_cpu(cpu_hotplug_state, cpu));
517                 if (oldstate != CPU_BROKEN)
518                         newstate = CPU_DEAD;
519                 else
520                         newstate = CPU_DEAD_FROZEN;
521         } while (atomic_cmpxchg(&per_cpu(cpu_hotplug_state, cpu),
522                                 oldstate, newstate) != oldstate);
523         return newstate == CPU_DEAD;
524 }
525
526 #endif /* #ifdef CONFIG_HOTPLUG_CPU */