bpf: widening for callback iterators
[platform/kernel/linux-starfive.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/sched/mm.h>
7 #include <linux/proc_fs.h>
8 #include <linux/smp.h>
9 #include <linux/init.h>
10 #include <linux/notifier.h>
11 #include <linux/sched/signal.h>
12 #include <linux/sched/hotplug.h>
13 #include <linux/sched/isolation.h>
14 #include <linux/sched/task.h>
15 #include <linux/sched/smt.h>
16 #include <linux/unistd.h>
17 #include <linux/cpu.h>
18 #include <linux/oom.h>
19 #include <linux/rcupdate.h>
20 #include <linux/delay.h>
21 #include <linux/export.h>
22 #include <linux/bug.h>
23 #include <linux/kthread.h>
24 #include <linux/stop_machine.h>
25 #include <linux/mutex.h>
26 #include <linux/gfp.h>
27 #include <linux/suspend.h>
28 #include <linux/lockdep.h>
29 #include <linux/tick.h>
30 #include <linux/irq.h>
31 #include <linux/nmi.h>
32 #include <linux/smpboot.h>
33 #include <linux/relay.h>
34 #include <linux/slab.h>
35 #include <linux/scs.h>
36 #include <linux/percpu-rwsem.h>
37 #include <linux/cpuset.h>
38 #include <linux/random.h>
39 #include <linux/cc_platform.h>
40
41 #include <trace/events/power.h>
42 #define CREATE_TRACE_POINTS
43 #include <trace/events/cpuhp.h>
44
45 #include "smpboot.h"
46
47 /**
48  * struct cpuhp_cpu_state - Per cpu hotplug state storage
49  * @state:      The current cpu state
50  * @target:     The target state
51  * @fail:       Current CPU hotplug callback state
52  * @thread:     Pointer to the hotplug thread
53  * @should_run: Thread should execute
54  * @rollback:   Perform a rollback
55  * @single:     Single callback invocation
56  * @bringup:    Single callback bringup or teardown selector
57  * @cpu:        CPU number
58  * @node:       Remote CPU node; for multi-instance, do a
59  *              single entry callback for install/remove
60  * @last:       For multi-instance rollback, remember how far we got
61  * @cb_state:   The state for a single callback (install/uninstall)
62  * @result:     Result of the operation
63  * @ap_sync_state:      State for AP synchronization
64  * @done_up:    Signal completion to the issuer of the task for cpu-up
65  * @done_down:  Signal completion to the issuer of the task for cpu-down
66  */
67 struct cpuhp_cpu_state {
68         enum cpuhp_state        state;
69         enum cpuhp_state        target;
70         enum cpuhp_state        fail;
71 #ifdef CONFIG_SMP
72         struct task_struct      *thread;
73         bool                    should_run;
74         bool                    rollback;
75         bool                    single;
76         bool                    bringup;
77         struct hlist_node       *node;
78         struct hlist_node       *last;
79         enum cpuhp_state        cb_state;
80         int                     result;
81         atomic_t                ap_sync_state;
82         struct completion       done_up;
83         struct completion       done_down;
84 #endif
85 };
86
87 static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
88         .fail = CPUHP_INVALID,
89 };
90
91 #ifdef CONFIG_SMP
92 cpumask_t cpus_booted_once_mask;
93 #endif
94
95 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
96 static struct lockdep_map cpuhp_state_up_map =
97         STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
98 static struct lockdep_map cpuhp_state_down_map =
99         STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
100
101
102 static inline void cpuhp_lock_acquire(bool bringup)
103 {
104         lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
105 }
106
107 static inline void cpuhp_lock_release(bool bringup)
108 {
109         lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
110 }
111 #else
112
113 static inline void cpuhp_lock_acquire(bool bringup) { }
114 static inline void cpuhp_lock_release(bool bringup) { }
115
116 #endif
117
118 /**
119  * struct cpuhp_step - Hotplug state machine step
120  * @name:       Name of the step
121  * @startup:    Startup function of the step
122  * @teardown:   Teardown function of the step
123  * @cant_stop:  Bringup/teardown can't be stopped at this step
124  * @multi_instance:     State has multiple instances which get added afterwards
125  */
126 struct cpuhp_step {
127         const char              *name;
128         union {
129                 int             (*single)(unsigned int cpu);
130                 int             (*multi)(unsigned int cpu,
131                                          struct hlist_node *node);
132         } startup;
133         union {
134                 int             (*single)(unsigned int cpu);
135                 int             (*multi)(unsigned int cpu,
136                                          struct hlist_node *node);
137         } teardown;
138         /* private: */
139         struct hlist_head       list;
140         /* public: */
141         bool                    cant_stop;
142         bool                    multi_instance;
143 };
144
145 static DEFINE_MUTEX(cpuhp_state_mutex);
146 static struct cpuhp_step cpuhp_hp_states[];
147
148 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
149 {
150         return cpuhp_hp_states + state;
151 }
152
153 static bool cpuhp_step_empty(bool bringup, struct cpuhp_step *step)
154 {
155         return bringup ? !step->startup.single : !step->teardown.single;
156 }
157
158 /**
159  * cpuhp_invoke_callback - Invoke the callbacks for a given state
160  * @cpu:        The cpu for which the callback should be invoked
161  * @state:      The state to do callbacks for
162  * @bringup:    True if the bringup callback should be invoked
163  * @node:       For multi-instance, do a single entry callback for install/remove
164  * @lastp:      For multi-instance rollback, remember how far we got
165  *
166  * Called from cpu hotplug and from the state register machinery.
167  *
168  * Return: %0 on success or a negative errno code
169  */
170 static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
171                                  bool bringup, struct hlist_node *node,
172                                  struct hlist_node **lastp)
173 {
174         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
175         struct cpuhp_step *step = cpuhp_get_step(state);
176         int (*cbm)(unsigned int cpu, struct hlist_node *node);
177         int (*cb)(unsigned int cpu);
178         int ret, cnt;
179
180         if (st->fail == state) {
181                 st->fail = CPUHP_INVALID;
182                 return -EAGAIN;
183         }
184
185         if (cpuhp_step_empty(bringup, step)) {
186                 WARN_ON_ONCE(1);
187                 return 0;
188         }
189
190         if (!step->multi_instance) {
191                 WARN_ON_ONCE(lastp && *lastp);
192                 cb = bringup ? step->startup.single : step->teardown.single;
193
194                 trace_cpuhp_enter(cpu, st->target, state, cb);
195                 ret = cb(cpu);
196                 trace_cpuhp_exit(cpu, st->state, state, ret);
197                 return ret;
198         }
199         cbm = bringup ? step->startup.multi : step->teardown.multi;
200
201         /* Single invocation for instance add/remove */
202         if (node) {
203                 WARN_ON_ONCE(lastp && *lastp);
204                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
205                 ret = cbm(cpu, node);
206                 trace_cpuhp_exit(cpu, st->state, state, ret);
207                 return ret;
208         }
209
210         /* State transition. Invoke on all instances */
211         cnt = 0;
212         hlist_for_each(node, &step->list) {
213                 if (lastp && node == *lastp)
214                         break;
215
216                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
217                 ret = cbm(cpu, node);
218                 trace_cpuhp_exit(cpu, st->state, state, ret);
219                 if (ret) {
220                         if (!lastp)
221                                 goto err;
222
223                         *lastp = node;
224                         return ret;
225                 }
226                 cnt++;
227         }
228         if (lastp)
229                 *lastp = NULL;
230         return 0;
231 err:
232         /* Rollback the instances if one failed */
233         cbm = !bringup ? step->startup.multi : step->teardown.multi;
234         if (!cbm)
235                 return ret;
236
237         hlist_for_each(node, &step->list) {
238                 if (!cnt--)
239                         break;
240
241                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
242                 ret = cbm(cpu, node);
243                 trace_cpuhp_exit(cpu, st->state, state, ret);
244                 /*
245                  * Rollback must not fail,
246                  */
247                 WARN_ON_ONCE(ret);
248         }
249         return ret;
250 }
251
252 #ifdef CONFIG_SMP
253 static bool cpuhp_is_ap_state(enum cpuhp_state state)
254 {
255         /*
256          * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
257          * purposes as that state is handled explicitly in cpu_down.
258          */
259         return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
260 }
261
262 static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
263 {
264         struct completion *done = bringup ? &st->done_up : &st->done_down;
265         wait_for_completion(done);
266 }
267
268 static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
269 {
270         struct completion *done = bringup ? &st->done_up : &st->done_down;
271         complete(done);
272 }
273
274 /*
275  * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
276  */
277 static bool cpuhp_is_atomic_state(enum cpuhp_state state)
278 {
279         return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
280 }
281
282 /* Synchronization state management */
283 enum cpuhp_sync_state {
284         SYNC_STATE_DEAD,
285         SYNC_STATE_KICKED,
286         SYNC_STATE_SHOULD_DIE,
287         SYNC_STATE_ALIVE,
288         SYNC_STATE_SHOULD_ONLINE,
289         SYNC_STATE_ONLINE,
290 };
291
292 #ifdef CONFIG_HOTPLUG_CORE_SYNC
293 /**
294  * cpuhp_ap_update_sync_state - Update synchronization state during bringup/teardown
295  * @state:      The synchronization state to set
296  *
297  * No synchronization point. Just update of the synchronization state, but implies
298  * a full barrier so that the AP changes are visible before the control CPU proceeds.
299  */
300 static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state)
301 {
302         atomic_t *st = this_cpu_ptr(&cpuhp_state.ap_sync_state);
303
304         (void)atomic_xchg(st, state);
305 }
306
307 void __weak arch_cpuhp_sync_state_poll(void) { cpu_relax(); }
308
309 static bool cpuhp_wait_for_sync_state(unsigned int cpu, enum cpuhp_sync_state state,
310                                       enum cpuhp_sync_state next_state)
311 {
312         atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
313         ktime_t now, end, start = ktime_get();
314         int sync;
315
316         end = start + 10ULL * NSEC_PER_SEC;
317
318         sync = atomic_read(st);
319         while (1) {
320                 if (sync == state) {
321                         if (!atomic_try_cmpxchg(st, &sync, next_state))
322                                 continue;
323                         return true;
324                 }
325
326                 now = ktime_get();
327                 if (now > end) {
328                         /* Timeout. Leave the state unchanged */
329                         return false;
330                 } else if (now - start < NSEC_PER_MSEC) {
331                         /* Poll for one millisecond */
332                         arch_cpuhp_sync_state_poll();
333                 } else {
334                         usleep_range_state(USEC_PER_MSEC, 2 * USEC_PER_MSEC, TASK_UNINTERRUPTIBLE);
335                 }
336                 sync = atomic_read(st);
337         }
338         return true;
339 }
340 #else  /* CONFIG_HOTPLUG_CORE_SYNC */
341 static inline void cpuhp_ap_update_sync_state(enum cpuhp_sync_state state) { }
342 #endif /* !CONFIG_HOTPLUG_CORE_SYNC */
343
344 #ifdef CONFIG_HOTPLUG_CORE_SYNC_DEAD
345 /**
346  * cpuhp_ap_report_dead - Update synchronization state to DEAD
347  *
348  * No synchronization point. Just update of the synchronization state.
349  */
350 void cpuhp_ap_report_dead(void)
351 {
352         cpuhp_ap_update_sync_state(SYNC_STATE_DEAD);
353 }
354
355 void __weak arch_cpuhp_cleanup_dead_cpu(unsigned int cpu) { }
356
357 /*
358  * Late CPU shutdown synchronization point. Cannot use cpuhp_state::done_down
359  * because the AP cannot issue complete() at this stage.
360  */
361 static void cpuhp_bp_sync_dead(unsigned int cpu)
362 {
363         atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
364         int sync = atomic_read(st);
365
366         do {
367                 /* CPU can have reported dead already. Don't overwrite that! */
368                 if (sync == SYNC_STATE_DEAD)
369                         break;
370         } while (!atomic_try_cmpxchg(st, &sync, SYNC_STATE_SHOULD_DIE));
371
372         if (cpuhp_wait_for_sync_state(cpu, SYNC_STATE_DEAD, SYNC_STATE_DEAD)) {
373                 /* CPU reached dead state. Invoke the cleanup function */
374                 arch_cpuhp_cleanup_dead_cpu(cpu);
375                 return;
376         }
377
378         /* No further action possible. Emit message and give up. */
379         pr_err("CPU%u failed to report dead state\n", cpu);
380 }
381 #else /* CONFIG_HOTPLUG_CORE_SYNC_DEAD */
382 static inline void cpuhp_bp_sync_dead(unsigned int cpu) { }
383 #endif /* !CONFIG_HOTPLUG_CORE_SYNC_DEAD */
384
385 #ifdef CONFIG_HOTPLUG_CORE_SYNC_FULL
386 /**
387  * cpuhp_ap_sync_alive - Synchronize AP with the control CPU once it is alive
388  *
389  * Updates the AP synchronization state to SYNC_STATE_ALIVE and waits
390  * for the BP to release it.
391  */
392 void cpuhp_ap_sync_alive(void)
393 {
394         atomic_t *st = this_cpu_ptr(&cpuhp_state.ap_sync_state);
395
396         cpuhp_ap_update_sync_state(SYNC_STATE_ALIVE);
397
398         /* Wait for the control CPU to release it. */
399         while (atomic_read(st) != SYNC_STATE_SHOULD_ONLINE)
400                 cpu_relax();
401 }
402
403 static bool cpuhp_can_boot_ap(unsigned int cpu)
404 {
405         atomic_t *st = per_cpu_ptr(&cpuhp_state.ap_sync_state, cpu);
406         int sync = atomic_read(st);
407
408 again:
409         switch (sync) {
410         case SYNC_STATE_DEAD:
411                 /* CPU is properly dead */
412                 break;
413         case SYNC_STATE_KICKED:
414                 /* CPU did not come up in previous attempt */
415                 break;
416         case SYNC_STATE_ALIVE:
417                 /* CPU is stuck cpuhp_ap_sync_alive(). */
418                 break;
419         default:
420                 /* CPU failed to report online or dead and is in limbo state. */
421                 return false;
422         }
423
424         /* Prepare for booting */
425         if (!atomic_try_cmpxchg(st, &sync, SYNC_STATE_KICKED))
426                 goto again;
427
428         return true;
429 }
430
431 void __weak arch_cpuhp_cleanup_kick_cpu(unsigned int cpu) { }
432
433 /*
434  * Early CPU bringup synchronization point. Cannot use cpuhp_state::done_up
435  * because the AP cannot issue complete() so early in the bringup.
436  */
437 static int cpuhp_bp_sync_alive(unsigned int cpu)
438 {
439         int ret = 0;
440
441         if (!IS_ENABLED(CONFIG_HOTPLUG_CORE_SYNC_FULL))
442                 return 0;
443
444         if (!cpuhp_wait_for_sync_state(cpu, SYNC_STATE_ALIVE, SYNC_STATE_SHOULD_ONLINE)) {
445                 pr_err("CPU%u failed to report alive state\n", cpu);
446                 ret = -EIO;
447         }
448
449         /* Let the architecture cleanup the kick alive mechanics. */
450         arch_cpuhp_cleanup_kick_cpu(cpu);
451         return ret;
452 }
453 #else /* CONFIG_HOTPLUG_CORE_SYNC_FULL */
454 static inline int cpuhp_bp_sync_alive(unsigned int cpu) { return 0; }
455 static inline bool cpuhp_can_boot_ap(unsigned int cpu) { return true; }
456 #endif /* !CONFIG_HOTPLUG_CORE_SYNC_FULL */
457
458 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
459 static DEFINE_MUTEX(cpu_add_remove_lock);
460 bool cpuhp_tasks_frozen;
461 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
462
463 /*
464  * The following two APIs (cpu_maps_update_begin/done) must be used when
465  * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
466  */
467 void cpu_maps_update_begin(void)
468 {
469         mutex_lock(&cpu_add_remove_lock);
470 }
471
472 void cpu_maps_update_done(void)
473 {
474         mutex_unlock(&cpu_add_remove_lock);
475 }
476
477 /*
478  * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
479  * Should always be manipulated under cpu_add_remove_lock
480  */
481 static int cpu_hotplug_disabled;
482
483 #ifdef CONFIG_HOTPLUG_CPU
484
485 DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
486
487 void cpus_read_lock(void)
488 {
489         percpu_down_read(&cpu_hotplug_lock);
490 }
491 EXPORT_SYMBOL_GPL(cpus_read_lock);
492
493 int cpus_read_trylock(void)
494 {
495         return percpu_down_read_trylock(&cpu_hotplug_lock);
496 }
497 EXPORT_SYMBOL_GPL(cpus_read_trylock);
498
499 void cpus_read_unlock(void)
500 {
501         percpu_up_read(&cpu_hotplug_lock);
502 }
503 EXPORT_SYMBOL_GPL(cpus_read_unlock);
504
505 void cpus_write_lock(void)
506 {
507         percpu_down_write(&cpu_hotplug_lock);
508 }
509
510 void cpus_write_unlock(void)
511 {
512         percpu_up_write(&cpu_hotplug_lock);
513 }
514
515 void lockdep_assert_cpus_held(void)
516 {
517         /*
518          * We can't have hotplug operations before userspace starts running,
519          * and some init codepaths will knowingly not take the hotplug lock.
520          * This is all valid, so mute lockdep until it makes sense to report
521          * unheld locks.
522          */
523         if (system_state < SYSTEM_RUNNING)
524                 return;
525
526         percpu_rwsem_assert_held(&cpu_hotplug_lock);
527 }
528
529 #ifdef CONFIG_LOCKDEP
530 int lockdep_is_cpus_held(void)
531 {
532         return percpu_rwsem_is_held(&cpu_hotplug_lock);
533 }
534 #endif
535
536 static void lockdep_acquire_cpus_lock(void)
537 {
538         rwsem_acquire(&cpu_hotplug_lock.dep_map, 0, 0, _THIS_IP_);
539 }
540
541 static void lockdep_release_cpus_lock(void)
542 {
543         rwsem_release(&cpu_hotplug_lock.dep_map, _THIS_IP_);
544 }
545
546 /*
547  * Wait for currently running CPU hotplug operations to complete (if any) and
548  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
549  * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
550  * hotplug path before performing hotplug operations. So acquiring that lock
551  * guarantees mutual exclusion from any currently running hotplug operations.
552  */
553 void cpu_hotplug_disable(void)
554 {
555         cpu_maps_update_begin();
556         cpu_hotplug_disabled++;
557         cpu_maps_update_done();
558 }
559 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
560
561 static void __cpu_hotplug_enable(void)
562 {
563         if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
564                 return;
565         cpu_hotplug_disabled--;
566 }
567
568 void cpu_hotplug_enable(void)
569 {
570         cpu_maps_update_begin();
571         __cpu_hotplug_enable();
572         cpu_maps_update_done();
573 }
574 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
575
576 #else
577
578 static void lockdep_acquire_cpus_lock(void)
579 {
580 }
581
582 static void lockdep_release_cpus_lock(void)
583 {
584 }
585
586 #endif  /* CONFIG_HOTPLUG_CPU */
587
588 /*
589  * Architectures that need SMT-specific errata handling during SMT hotplug
590  * should override this.
591  */
592 void __weak arch_smt_update(void) { }
593
594 #ifdef CONFIG_HOTPLUG_SMT
595
596 enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
597 static unsigned int cpu_smt_max_threads __ro_after_init;
598 unsigned int cpu_smt_num_threads __read_mostly = UINT_MAX;
599
600 void __init cpu_smt_disable(bool force)
601 {
602         if (!cpu_smt_possible())
603                 return;
604
605         if (force) {
606                 pr_info("SMT: Force disabled\n");
607                 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
608         } else {
609                 pr_info("SMT: disabled\n");
610                 cpu_smt_control = CPU_SMT_DISABLED;
611         }
612         cpu_smt_num_threads = 1;
613 }
614
615 /*
616  * The decision whether SMT is supported can only be done after the full
617  * CPU identification. Called from architecture code.
618  */
619 void __init cpu_smt_set_num_threads(unsigned int num_threads,
620                                     unsigned int max_threads)
621 {
622         WARN_ON(!num_threads || (num_threads > max_threads));
623
624         if (max_threads == 1)
625                 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
626
627         cpu_smt_max_threads = max_threads;
628
629         /*
630          * If SMT has been disabled via the kernel command line or SMT is
631          * not supported, set cpu_smt_num_threads to 1 for consistency.
632          * If enabled, take the architecture requested number of threads
633          * to bring up into account.
634          */
635         if (cpu_smt_control != CPU_SMT_ENABLED)
636                 cpu_smt_num_threads = 1;
637         else if (num_threads < cpu_smt_num_threads)
638                 cpu_smt_num_threads = num_threads;
639 }
640
641 static int __init smt_cmdline_disable(char *str)
642 {
643         cpu_smt_disable(str && !strcmp(str, "force"));
644         return 0;
645 }
646 early_param("nosmt", smt_cmdline_disable);
647
648 /*
649  * For Archicture supporting partial SMT states check if the thread is allowed.
650  * Otherwise this has already been checked through cpu_smt_max_threads when
651  * setting the SMT level.
652  */
653 static inline bool cpu_smt_thread_allowed(unsigned int cpu)
654 {
655 #ifdef CONFIG_SMT_NUM_THREADS_DYNAMIC
656         return topology_smt_thread_allowed(cpu);
657 #else
658         return true;
659 #endif
660 }
661
662 static inline bool cpu_bootable(unsigned int cpu)
663 {
664         if (cpu_smt_control == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
665                 return true;
666
667         /* All CPUs are bootable if controls are not configured */
668         if (cpu_smt_control == CPU_SMT_NOT_IMPLEMENTED)
669                 return true;
670
671         /* All CPUs are bootable if CPU is not SMT capable */
672         if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
673                 return true;
674
675         if (topology_is_primary_thread(cpu))
676                 return true;
677
678         /*
679          * On x86 it's required to boot all logical CPUs at least once so
680          * that the init code can get a chance to set CR4.MCE on each
681          * CPU. Otherwise, a broadcasted MCE observing CR4.MCE=0b on any
682          * core will shutdown the machine.
683          */
684         return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
685 }
686
687 /* Returns true if SMT is supported and not forcefully (irreversibly) disabled */
688 bool cpu_smt_possible(void)
689 {
690         return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
691                 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
692 }
693 EXPORT_SYMBOL_GPL(cpu_smt_possible);
694
695 #else
696 static inline bool cpu_bootable(unsigned int cpu) { return true; }
697 #endif
698
699 static inline enum cpuhp_state
700 cpuhp_set_state(int cpu, struct cpuhp_cpu_state *st, enum cpuhp_state target)
701 {
702         enum cpuhp_state prev_state = st->state;
703         bool bringup = st->state < target;
704
705         st->rollback = false;
706         st->last = NULL;
707
708         st->target = target;
709         st->single = false;
710         st->bringup = bringup;
711         if (cpu_dying(cpu) != !bringup)
712                 set_cpu_dying(cpu, !bringup);
713
714         return prev_state;
715 }
716
717 static inline void
718 cpuhp_reset_state(int cpu, struct cpuhp_cpu_state *st,
719                   enum cpuhp_state prev_state)
720 {
721         bool bringup = !st->bringup;
722
723         st->target = prev_state;
724
725         /*
726          * Already rolling back. No need invert the bringup value or to change
727          * the current state.
728          */
729         if (st->rollback)
730                 return;
731
732         st->rollback = true;
733
734         /*
735          * If we have st->last we need to undo partial multi_instance of this
736          * state first. Otherwise start undo at the previous state.
737          */
738         if (!st->last) {
739                 if (st->bringup)
740                         st->state--;
741                 else
742                         st->state++;
743         }
744
745         st->bringup = bringup;
746         if (cpu_dying(cpu) != !bringup)
747                 set_cpu_dying(cpu, !bringup);
748 }
749
750 /* Regular hotplug invocation of the AP hotplug thread */
751 static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
752 {
753         if (!st->single && st->state == st->target)
754                 return;
755
756         st->result = 0;
757         /*
758          * Make sure the above stores are visible before should_run becomes
759          * true. Paired with the mb() above in cpuhp_thread_fun()
760          */
761         smp_mb();
762         st->should_run = true;
763         wake_up_process(st->thread);
764         wait_for_ap_thread(st, st->bringup);
765 }
766
767 static int cpuhp_kick_ap(int cpu, struct cpuhp_cpu_state *st,
768                          enum cpuhp_state target)
769 {
770         enum cpuhp_state prev_state;
771         int ret;
772
773         prev_state = cpuhp_set_state(cpu, st, target);
774         __cpuhp_kick_ap(st);
775         if ((ret = st->result)) {
776                 cpuhp_reset_state(cpu, st, prev_state);
777                 __cpuhp_kick_ap(st);
778         }
779
780         return ret;
781 }
782
783 static int bringup_wait_for_ap_online(unsigned int cpu)
784 {
785         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
786
787         /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
788         wait_for_ap_thread(st, true);
789         if (WARN_ON_ONCE((!cpu_online(cpu))))
790                 return -ECANCELED;
791
792         /* Unpark the hotplug thread of the target cpu */
793         kthread_unpark(st->thread);
794
795         /*
796          * SMT soft disabling on X86 requires to bring the CPU out of the
797          * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit.  The
798          * CPU marked itself as booted_once in notify_cpu_starting() so the
799          * cpu_bootable() check will now return false if this is not the
800          * primary sibling.
801          */
802         if (!cpu_bootable(cpu))
803                 return -ECANCELED;
804         return 0;
805 }
806
807 #ifdef CONFIG_HOTPLUG_SPLIT_STARTUP
808 static int cpuhp_kick_ap_alive(unsigned int cpu)
809 {
810         if (!cpuhp_can_boot_ap(cpu))
811                 return -EAGAIN;
812
813         return arch_cpuhp_kick_ap_alive(cpu, idle_thread_get(cpu));
814 }
815
816 static int cpuhp_bringup_ap(unsigned int cpu)
817 {
818         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
819         int ret;
820
821         /*
822          * Some architectures have to walk the irq descriptors to
823          * setup the vector space for the cpu which comes online.
824          * Prevent irq alloc/free across the bringup.
825          */
826         irq_lock_sparse();
827
828         ret = cpuhp_bp_sync_alive(cpu);
829         if (ret)
830                 goto out_unlock;
831
832         ret = bringup_wait_for_ap_online(cpu);
833         if (ret)
834                 goto out_unlock;
835
836         irq_unlock_sparse();
837
838         if (st->target <= CPUHP_AP_ONLINE_IDLE)
839                 return 0;
840
841         return cpuhp_kick_ap(cpu, st, st->target);
842
843 out_unlock:
844         irq_unlock_sparse();
845         return ret;
846 }
847 #else
848 static int bringup_cpu(unsigned int cpu)
849 {
850         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
851         struct task_struct *idle = idle_thread_get(cpu);
852         int ret;
853
854         if (!cpuhp_can_boot_ap(cpu))
855                 return -EAGAIN;
856
857         /*
858          * Some architectures have to walk the irq descriptors to
859          * setup the vector space for the cpu which comes online.
860          *
861          * Prevent irq alloc/free across the bringup by acquiring the
862          * sparse irq lock. Hold it until the upcoming CPU completes the
863          * startup in cpuhp_online_idle() which allows to avoid
864          * intermediate synchronization points in the architecture code.
865          */
866         irq_lock_sparse();
867
868         ret = __cpu_up(cpu, idle);
869         if (ret)
870                 goto out_unlock;
871
872         ret = cpuhp_bp_sync_alive(cpu);
873         if (ret)
874                 goto out_unlock;
875
876         ret = bringup_wait_for_ap_online(cpu);
877         if (ret)
878                 goto out_unlock;
879
880         irq_unlock_sparse();
881
882         if (st->target <= CPUHP_AP_ONLINE_IDLE)
883                 return 0;
884
885         return cpuhp_kick_ap(cpu, st, st->target);
886
887 out_unlock:
888         irq_unlock_sparse();
889         return ret;
890 }
891 #endif
892
893 static int finish_cpu(unsigned int cpu)
894 {
895         struct task_struct *idle = idle_thread_get(cpu);
896         struct mm_struct *mm = idle->active_mm;
897
898         /*
899          * idle_task_exit() will have switched to &init_mm, now
900          * clean up any remaining active_mm state.
901          */
902         if (mm != &init_mm)
903                 idle->active_mm = &init_mm;
904         mmdrop_lazy_tlb(mm);
905         return 0;
906 }
907
908 /*
909  * Hotplug state machine related functions
910  */
911
912 /*
913  * Get the next state to run. Empty ones will be skipped. Returns true if a
914  * state must be run.
915  *
916  * st->state will be modified ahead of time, to match state_to_run, as if it
917  * has already ran.
918  */
919 static bool cpuhp_next_state(bool bringup,
920                              enum cpuhp_state *state_to_run,
921                              struct cpuhp_cpu_state *st,
922                              enum cpuhp_state target)
923 {
924         do {
925                 if (bringup) {
926                         if (st->state >= target)
927                                 return false;
928
929                         *state_to_run = ++st->state;
930                 } else {
931                         if (st->state <= target)
932                                 return false;
933
934                         *state_to_run = st->state--;
935                 }
936
937                 if (!cpuhp_step_empty(bringup, cpuhp_get_step(*state_to_run)))
938                         break;
939         } while (true);
940
941         return true;
942 }
943
944 static int __cpuhp_invoke_callback_range(bool bringup,
945                                          unsigned int cpu,
946                                          struct cpuhp_cpu_state *st,
947                                          enum cpuhp_state target,
948                                          bool nofail)
949 {
950         enum cpuhp_state state;
951         int ret = 0;
952
953         while (cpuhp_next_state(bringup, &state, st, target)) {
954                 int err;
955
956                 err = cpuhp_invoke_callback(cpu, state, bringup, NULL, NULL);
957                 if (!err)
958                         continue;
959
960                 if (nofail) {
961                         pr_warn("CPU %u %s state %s (%d) failed (%d)\n",
962                                 cpu, bringup ? "UP" : "DOWN",
963                                 cpuhp_get_step(st->state)->name,
964                                 st->state, err);
965                         ret = -1;
966                 } else {
967                         ret = err;
968                         break;
969                 }
970         }
971
972         return ret;
973 }
974
975 static inline int cpuhp_invoke_callback_range(bool bringup,
976                                               unsigned int cpu,
977                                               struct cpuhp_cpu_state *st,
978                                               enum cpuhp_state target)
979 {
980         return __cpuhp_invoke_callback_range(bringup, cpu, st, target, false);
981 }
982
983 static inline void cpuhp_invoke_callback_range_nofail(bool bringup,
984                                                       unsigned int cpu,
985                                                       struct cpuhp_cpu_state *st,
986                                                       enum cpuhp_state target)
987 {
988         __cpuhp_invoke_callback_range(bringup, cpu, st, target, true);
989 }
990
991 static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
992 {
993         if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
994                 return true;
995         /*
996          * When CPU hotplug is disabled, then taking the CPU down is not
997          * possible because takedown_cpu() and the architecture and
998          * subsystem specific mechanisms are not available. So the CPU
999          * which would be completely unplugged again needs to stay around
1000          * in the current state.
1001          */
1002         return st->state <= CPUHP_BRINGUP_CPU;
1003 }
1004
1005 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1006                               enum cpuhp_state target)
1007 {
1008         enum cpuhp_state prev_state = st->state;
1009         int ret = 0;
1010
1011         ret = cpuhp_invoke_callback_range(true, cpu, st, target);
1012         if (ret) {
1013                 pr_debug("CPU UP failed (%d) CPU %u state %s (%d)\n",
1014                          ret, cpu, cpuhp_get_step(st->state)->name,
1015                          st->state);
1016
1017                 cpuhp_reset_state(cpu, st, prev_state);
1018                 if (can_rollback_cpu(st))
1019                         WARN_ON(cpuhp_invoke_callback_range(false, cpu, st,
1020                                                             prev_state));
1021         }
1022         return ret;
1023 }
1024
1025 /*
1026  * The cpu hotplug threads manage the bringup and teardown of the cpus
1027  */
1028 static int cpuhp_should_run(unsigned int cpu)
1029 {
1030         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1031
1032         return st->should_run;
1033 }
1034
1035 /*
1036  * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
1037  * callbacks when a state gets [un]installed at runtime.
1038  *
1039  * Each invocation of this function by the smpboot thread does a single AP
1040  * state callback.
1041  *
1042  * It has 3 modes of operation:
1043  *  - single: runs st->cb_state
1044  *  - up:     runs ++st->state, while st->state < st->target
1045  *  - down:   runs st->state--, while st->state > st->target
1046  *
1047  * When complete or on error, should_run is cleared and the completion is fired.
1048  */
1049 static void cpuhp_thread_fun(unsigned int cpu)
1050 {
1051         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1052         bool bringup = st->bringup;
1053         enum cpuhp_state state;
1054
1055         if (WARN_ON_ONCE(!st->should_run))
1056                 return;
1057
1058         /*
1059          * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
1060          * that if we see ->should_run we also see the rest of the state.
1061          */
1062         smp_mb();
1063
1064         /*
1065          * The BP holds the hotplug lock, but we're now running on the AP,
1066          * ensure that anybody asserting the lock is held, will actually find
1067          * it so.
1068          */
1069         lockdep_acquire_cpus_lock();
1070         cpuhp_lock_acquire(bringup);
1071
1072         if (st->single) {
1073                 state = st->cb_state;
1074                 st->should_run = false;
1075         } else {
1076                 st->should_run = cpuhp_next_state(bringup, &state, st, st->target);
1077                 if (!st->should_run)
1078                         goto end;
1079         }
1080
1081         WARN_ON_ONCE(!cpuhp_is_ap_state(state));
1082
1083         if (cpuhp_is_atomic_state(state)) {
1084                 local_irq_disable();
1085                 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
1086                 local_irq_enable();
1087
1088                 /*
1089                  * STARTING/DYING must not fail!
1090                  */
1091                 WARN_ON_ONCE(st->result);
1092         } else {
1093                 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
1094         }
1095
1096         if (st->result) {
1097                 /*
1098                  * If we fail on a rollback, we're up a creek without no
1099                  * paddle, no way forward, no way back. We loose, thanks for
1100                  * playing.
1101                  */
1102                 WARN_ON_ONCE(st->rollback);
1103                 st->should_run = false;
1104         }
1105
1106 end:
1107         cpuhp_lock_release(bringup);
1108         lockdep_release_cpus_lock();
1109
1110         if (!st->should_run)
1111                 complete_ap_thread(st, bringup);
1112 }
1113
1114 /* Invoke a single callback on a remote cpu */
1115 static int
1116 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
1117                          struct hlist_node *node)
1118 {
1119         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1120         int ret;
1121
1122         if (!cpu_online(cpu))
1123                 return 0;
1124
1125         cpuhp_lock_acquire(false);
1126         cpuhp_lock_release(false);
1127
1128         cpuhp_lock_acquire(true);
1129         cpuhp_lock_release(true);
1130
1131         /*
1132          * If we are up and running, use the hotplug thread. For early calls
1133          * we invoke the thread function directly.
1134          */
1135         if (!st->thread)
1136                 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1137
1138         st->rollback = false;
1139         st->last = NULL;
1140
1141         st->node = node;
1142         st->bringup = bringup;
1143         st->cb_state = state;
1144         st->single = true;
1145
1146         __cpuhp_kick_ap(st);
1147
1148         /*
1149          * If we failed and did a partial, do a rollback.
1150          */
1151         if ((ret = st->result) && st->last) {
1152                 st->rollback = true;
1153                 st->bringup = !bringup;
1154
1155                 __cpuhp_kick_ap(st);
1156         }
1157
1158         /*
1159          * Clean up the leftovers so the next hotplug operation wont use stale
1160          * data.
1161          */
1162         st->node = st->last = NULL;
1163         return ret;
1164 }
1165
1166 static int cpuhp_kick_ap_work(unsigned int cpu)
1167 {
1168         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1169         enum cpuhp_state prev_state = st->state;
1170         int ret;
1171
1172         cpuhp_lock_acquire(false);
1173         cpuhp_lock_release(false);
1174
1175         cpuhp_lock_acquire(true);
1176         cpuhp_lock_release(true);
1177
1178         trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
1179         ret = cpuhp_kick_ap(cpu, st, st->target);
1180         trace_cpuhp_exit(cpu, st->state, prev_state, ret);
1181
1182         return ret;
1183 }
1184
1185 static struct smp_hotplug_thread cpuhp_threads = {
1186         .store                  = &cpuhp_state.thread,
1187         .thread_should_run      = cpuhp_should_run,
1188         .thread_fn              = cpuhp_thread_fun,
1189         .thread_comm            = "cpuhp/%u",
1190         .selfparking            = true,
1191 };
1192
1193 static __init void cpuhp_init_state(void)
1194 {
1195         struct cpuhp_cpu_state *st;
1196         int cpu;
1197
1198         for_each_possible_cpu(cpu) {
1199                 st = per_cpu_ptr(&cpuhp_state, cpu);
1200                 init_completion(&st->done_up);
1201                 init_completion(&st->done_down);
1202         }
1203 }
1204
1205 void __init cpuhp_threads_init(void)
1206 {
1207         cpuhp_init_state();
1208         BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
1209         kthread_unpark(this_cpu_read(cpuhp_state.thread));
1210 }
1211
1212 /*
1213  *
1214  * Serialize hotplug trainwrecks outside of the cpu_hotplug_lock
1215  * protected region.
1216  *
1217  * The operation is still serialized against concurrent CPU hotplug via
1218  * cpu_add_remove_lock, i.e. CPU map protection.  But it is _not_
1219  * serialized against other hotplug related activity like adding or
1220  * removing of state callbacks and state instances, which invoke either the
1221  * startup or the teardown callback of the affected state.
1222  *
1223  * This is required for subsystems which are unfixable vs. CPU hotplug and
1224  * evade lock inversion problems by scheduling work which has to be
1225  * completed _before_ cpu_up()/_cpu_down() returns.
1226  *
1227  * Don't even think about adding anything to this for any new code or even
1228  * drivers. It's only purpose is to keep existing lock order trainwrecks
1229  * working.
1230  *
1231  * For cpu_down() there might be valid reasons to finish cleanups which are
1232  * not required to be done under cpu_hotplug_lock, but that's a different
1233  * story and would be not invoked via this.
1234  */
1235 static void cpu_up_down_serialize_trainwrecks(bool tasks_frozen)
1236 {
1237         /*
1238          * cpusets delegate hotplug operations to a worker to "solve" the
1239          * lock order problems. Wait for the worker, but only if tasks are
1240          * _not_ frozen (suspend, hibernate) as that would wait forever.
1241          *
1242          * The wait is required because otherwise the hotplug operation
1243          * returns with inconsistent state, which could even be observed in
1244          * user space when a new CPU is brought up. The CPU plug uevent
1245          * would be delivered and user space reacting on it would fail to
1246          * move tasks to the newly plugged CPU up to the point where the
1247          * work has finished because up to that point the newly plugged CPU
1248          * is not assignable in cpusets/cgroups. On unplug that's not
1249          * necessarily a visible issue, but it is still inconsistent state,
1250          * which is the real problem which needs to be "fixed". This can't
1251          * prevent the transient state between scheduling the work and
1252          * returning from waiting for it.
1253          */
1254         if (!tasks_frozen)
1255                 cpuset_wait_for_hotplug();
1256 }
1257
1258 #ifdef CONFIG_HOTPLUG_CPU
1259 #ifndef arch_clear_mm_cpumask_cpu
1260 #define arch_clear_mm_cpumask_cpu(cpu, mm) cpumask_clear_cpu(cpu, mm_cpumask(mm))
1261 #endif
1262
1263 /**
1264  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
1265  * @cpu: a CPU id
1266  *
1267  * This function walks all processes, finds a valid mm struct for each one and
1268  * then clears a corresponding bit in mm's cpumask.  While this all sounds
1269  * trivial, there are various non-obvious corner cases, which this function
1270  * tries to solve in a safe manner.
1271  *
1272  * Also note that the function uses a somewhat relaxed locking scheme, so it may
1273  * be called only for an already offlined CPU.
1274  */
1275 void clear_tasks_mm_cpumask(int cpu)
1276 {
1277         struct task_struct *p;
1278
1279         /*
1280          * This function is called after the cpu is taken down and marked
1281          * offline, so its not like new tasks will ever get this cpu set in
1282          * their mm mask. -- Peter Zijlstra
1283          * Thus, we may use rcu_read_lock() here, instead of grabbing
1284          * full-fledged tasklist_lock.
1285          */
1286         WARN_ON(cpu_online(cpu));
1287         rcu_read_lock();
1288         for_each_process(p) {
1289                 struct task_struct *t;
1290
1291                 /*
1292                  * Main thread might exit, but other threads may still have
1293                  * a valid mm. Find one.
1294                  */
1295                 t = find_lock_task_mm(p);
1296                 if (!t)
1297                         continue;
1298                 arch_clear_mm_cpumask_cpu(cpu, t->mm);
1299                 task_unlock(t);
1300         }
1301         rcu_read_unlock();
1302 }
1303
1304 /* Take this CPU down. */
1305 static int take_cpu_down(void *_param)
1306 {
1307         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1308         enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
1309         int err, cpu = smp_processor_id();
1310
1311         /* Ensure this CPU doesn't handle any more interrupts. */
1312         err = __cpu_disable();
1313         if (err < 0)
1314                 return err;
1315
1316         /*
1317          * Must be called from CPUHP_TEARDOWN_CPU, which means, as we are going
1318          * down, that the current state is CPUHP_TEARDOWN_CPU - 1.
1319          */
1320         WARN_ON(st->state != (CPUHP_TEARDOWN_CPU - 1));
1321
1322         /*
1323          * Invoke the former CPU_DYING callbacks. DYING must not fail!
1324          */
1325         cpuhp_invoke_callback_range_nofail(false, cpu, st, target);
1326
1327         /* Give up timekeeping duties */
1328         tick_handover_do_timer();
1329         /* Remove CPU from timer broadcasting */
1330         tick_offline_cpu(cpu);
1331         /* Park the stopper thread */
1332         stop_machine_park(cpu);
1333         return 0;
1334 }
1335
1336 static int takedown_cpu(unsigned int cpu)
1337 {
1338         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1339         int err;
1340
1341         /* Park the smpboot threads */
1342         kthread_park(st->thread);
1343
1344         /*
1345          * Prevent irq alloc/free while the dying cpu reorganizes the
1346          * interrupt affinities.
1347          */
1348         irq_lock_sparse();
1349
1350         /*
1351          * So now all preempt/rcu users must observe !cpu_active().
1352          */
1353         err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
1354         if (err) {
1355                 /* CPU refused to die */
1356                 irq_unlock_sparse();
1357                 /* Unpark the hotplug thread so we can rollback there */
1358                 kthread_unpark(st->thread);
1359                 return err;
1360         }
1361         BUG_ON(cpu_online(cpu));
1362
1363         /*
1364          * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
1365          * all runnable tasks from the CPU, there's only the idle task left now
1366          * that the migration thread is done doing the stop_machine thing.
1367          *
1368          * Wait for the stop thread to go away.
1369          */
1370         wait_for_ap_thread(st, false);
1371         BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
1372
1373         /* Interrupts are moved away from the dying cpu, reenable alloc/free */
1374         irq_unlock_sparse();
1375
1376         hotplug_cpu__broadcast_tick_pull(cpu);
1377         /* This actually kills the CPU. */
1378         __cpu_die(cpu);
1379
1380         cpuhp_bp_sync_dead(cpu);
1381
1382         tick_cleanup_dead_cpu(cpu);
1383         rcutree_migrate_callbacks(cpu);
1384         return 0;
1385 }
1386
1387 static void cpuhp_complete_idle_dead(void *arg)
1388 {
1389         struct cpuhp_cpu_state *st = arg;
1390
1391         complete_ap_thread(st, false);
1392 }
1393
1394 void cpuhp_report_idle_dead(void)
1395 {
1396         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1397
1398         BUG_ON(st->state != CPUHP_AP_OFFLINE);
1399         rcu_report_dead(smp_processor_id());
1400         st->state = CPUHP_AP_IDLE_DEAD;
1401         /*
1402          * We cannot call complete after rcu_report_dead() so we delegate it
1403          * to an online cpu.
1404          */
1405         smp_call_function_single(cpumask_first(cpu_online_mask),
1406                                  cpuhp_complete_idle_dead, st, 0);
1407 }
1408
1409 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
1410                                 enum cpuhp_state target)
1411 {
1412         enum cpuhp_state prev_state = st->state;
1413         int ret = 0;
1414
1415         ret = cpuhp_invoke_callback_range(false, cpu, st, target);
1416         if (ret) {
1417                 pr_debug("CPU DOWN failed (%d) CPU %u state %s (%d)\n",
1418                          ret, cpu, cpuhp_get_step(st->state)->name,
1419                          st->state);
1420
1421                 cpuhp_reset_state(cpu, st, prev_state);
1422
1423                 if (st->state < prev_state)
1424                         WARN_ON(cpuhp_invoke_callback_range(true, cpu, st,
1425                                                             prev_state));
1426         }
1427
1428         return ret;
1429 }
1430
1431 /* Requires cpu_add_remove_lock to be held */
1432 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
1433                            enum cpuhp_state target)
1434 {
1435         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1436         int prev_state, ret = 0;
1437
1438         if (num_online_cpus() == 1)
1439                 return -EBUSY;
1440
1441         if (!cpu_present(cpu))
1442                 return -EINVAL;
1443
1444         cpus_write_lock();
1445
1446         cpuhp_tasks_frozen = tasks_frozen;
1447
1448         prev_state = cpuhp_set_state(cpu, st, target);
1449         /*
1450          * If the current CPU state is in the range of the AP hotplug thread,
1451          * then we need to kick the thread.
1452          */
1453         if (st->state > CPUHP_TEARDOWN_CPU) {
1454                 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
1455                 ret = cpuhp_kick_ap_work(cpu);
1456                 /*
1457                  * The AP side has done the error rollback already. Just
1458                  * return the error code..
1459                  */
1460                 if (ret)
1461                         goto out;
1462
1463                 /*
1464                  * We might have stopped still in the range of the AP hotplug
1465                  * thread. Nothing to do anymore.
1466                  */
1467                 if (st->state > CPUHP_TEARDOWN_CPU)
1468                         goto out;
1469
1470                 st->target = target;
1471         }
1472         /*
1473          * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1474          * to do the further cleanups.
1475          */
1476         ret = cpuhp_down_callbacks(cpu, st, target);
1477         if (ret && st->state < prev_state) {
1478                 if (st->state == CPUHP_TEARDOWN_CPU) {
1479                         cpuhp_reset_state(cpu, st, prev_state);
1480                         __cpuhp_kick_ap(st);
1481                 } else {
1482                         WARN(1, "DEAD callback error for CPU%d", cpu);
1483                 }
1484         }
1485
1486 out:
1487         cpus_write_unlock();
1488         /*
1489          * Do post unplug cleanup. This is still protected against
1490          * concurrent CPU hotplug via cpu_add_remove_lock.
1491          */
1492         lockup_detector_cleanup();
1493         arch_smt_update();
1494         cpu_up_down_serialize_trainwrecks(tasks_frozen);
1495         return ret;
1496 }
1497
1498 struct cpu_down_work {
1499         unsigned int            cpu;
1500         enum cpuhp_state        target;
1501 };
1502
1503 static long __cpu_down_maps_locked(void *arg)
1504 {
1505         struct cpu_down_work *work = arg;
1506
1507         return _cpu_down(work->cpu, 0, work->target);
1508 }
1509
1510 static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1511 {
1512         struct cpu_down_work work = { .cpu = cpu, .target = target, };
1513
1514         /*
1515          * If the platform does not support hotplug, report it explicitly to
1516          * differentiate it from a transient offlining failure.
1517          */
1518         if (cc_platform_has(CC_ATTR_HOTPLUG_DISABLED))
1519                 return -EOPNOTSUPP;
1520         if (cpu_hotplug_disabled)
1521                 return -EBUSY;
1522
1523         /*
1524          * Ensure that the control task does not run on the to be offlined
1525          * CPU to prevent a deadlock against cfs_b->period_timer.
1526          * Also keep at least one housekeeping cpu onlined to avoid generating
1527          * an empty sched_domain span.
1528          */
1529         for_each_cpu_and(cpu, cpu_online_mask, housekeeping_cpumask(HK_TYPE_DOMAIN)) {
1530                 if (cpu != work.cpu)
1531                         return work_on_cpu(cpu, __cpu_down_maps_locked, &work);
1532         }
1533         return -EBUSY;
1534 }
1535
1536 static int cpu_down(unsigned int cpu, enum cpuhp_state target)
1537 {
1538         int err;
1539
1540         cpu_maps_update_begin();
1541         err = cpu_down_maps_locked(cpu, target);
1542         cpu_maps_update_done();
1543         return err;
1544 }
1545
1546 /**
1547  * cpu_device_down - Bring down a cpu device
1548  * @dev: Pointer to the cpu device to offline
1549  *
1550  * This function is meant to be used by device core cpu subsystem only.
1551  *
1552  * Other subsystems should use remove_cpu() instead.
1553  *
1554  * Return: %0 on success or a negative errno code
1555  */
1556 int cpu_device_down(struct device *dev)
1557 {
1558         return cpu_down(dev->id, CPUHP_OFFLINE);
1559 }
1560
1561 int remove_cpu(unsigned int cpu)
1562 {
1563         int ret;
1564
1565         lock_device_hotplug();
1566         ret = device_offline(get_cpu_device(cpu));
1567         unlock_device_hotplug();
1568
1569         return ret;
1570 }
1571 EXPORT_SYMBOL_GPL(remove_cpu);
1572
1573 void smp_shutdown_nonboot_cpus(unsigned int primary_cpu)
1574 {
1575         unsigned int cpu;
1576         int error;
1577
1578         cpu_maps_update_begin();
1579
1580         /*
1581          * Make certain the cpu I'm about to reboot on is online.
1582          *
1583          * This is inline to what migrate_to_reboot_cpu() already do.
1584          */
1585         if (!cpu_online(primary_cpu))
1586                 primary_cpu = cpumask_first(cpu_online_mask);
1587
1588         for_each_online_cpu(cpu) {
1589                 if (cpu == primary_cpu)
1590                         continue;
1591
1592                 error = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1593                 if (error) {
1594                         pr_err("Failed to offline CPU%d - error=%d",
1595                                 cpu, error);
1596                         break;
1597                 }
1598         }
1599
1600         /*
1601          * Ensure all but the reboot CPU are offline.
1602          */
1603         BUG_ON(num_online_cpus() > 1);
1604
1605         /*
1606          * Make sure the CPUs won't be enabled by someone else after this
1607          * point. Kexec will reboot to a new kernel shortly resetting
1608          * everything along the way.
1609          */
1610         cpu_hotplug_disabled++;
1611
1612         cpu_maps_update_done();
1613 }
1614
1615 #else
1616 #define takedown_cpu            NULL
1617 #endif /*CONFIG_HOTPLUG_CPU*/
1618
1619 /**
1620  * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1621  * @cpu: cpu that just started
1622  *
1623  * It must be called by the arch code on the new cpu, before the new cpu
1624  * enables interrupts and before the "boot" cpu returns from __cpu_up().
1625  */
1626 void notify_cpu_starting(unsigned int cpu)
1627 {
1628         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1629         enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1630
1631         rcu_cpu_starting(cpu);  /* Enables RCU usage on this CPU. */
1632         cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1633
1634         /*
1635          * STARTING must not fail!
1636          */
1637         cpuhp_invoke_callback_range_nofail(true, cpu, st, target);
1638 }
1639
1640 /*
1641  * Called from the idle task. Wake up the controlling task which brings the
1642  * hotplug thread of the upcoming CPU up and then delegates the rest of the
1643  * online bringup to the hotplug thread.
1644  */
1645 void cpuhp_online_idle(enum cpuhp_state state)
1646 {
1647         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1648
1649         /* Happens for the boot cpu */
1650         if (state != CPUHP_AP_ONLINE_IDLE)
1651                 return;
1652
1653         cpuhp_ap_update_sync_state(SYNC_STATE_ONLINE);
1654
1655         /*
1656          * Unpark the stopper thread before we start the idle loop (and start
1657          * scheduling); this ensures the stopper task is always available.
1658          */
1659         stop_machine_unpark(smp_processor_id());
1660
1661         st->state = CPUHP_AP_ONLINE_IDLE;
1662         complete_ap_thread(st, true);
1663 }
1664
1665 /* Requires cpu_add_remove_lock to be held */
1666 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1667 {
1668         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1669         struct task_struct *idle;
1670         int ret = 0;
1671
1672         cpus_write_lock();
1673
1674         if (!cpu_present(cpu)) {
1675                 ret = -EINVAL;
1676                 goto out;
1677         }
1678
1679         /*
1680          * The caller of cpu_up() might have raced with another
1681          * caller. Nothing to do.
1682          */
1683         if (st->state >= target)
1684                 goto out;
1685
1686         if (st->state == CPUHP_OFFLINE) {
1687                 /* Let it fail before we try to bring the cpu up */
1688                 idle = idle_thread_get(cpu);
1689                 if (IS_ERR(idle)) {
1690                         ret = PTR_ERR(idle);
1691                         goto out;
1692                 }
1693
1694                 /*
1695                  * Reset stale stack state from the last time this CPU was online.
1696                  */
1697                 scs_task_reset(idle);
1698                 kasan_unpoison_task_stack(idle);
1699         }
1700
1701         cpuhp_tasks_frozen = tasks_frozen;
1702
1703         cpuhp_set_state(cpu, st, target);
1704         /*
1705          * If the current CPU state is in the range of the AP hotplug thread,
1706          * then we need to kick the thread once more.
1707          */
1708         if (st->state > CPUHP_BRINGUP_CPU) {
1709                 ret = cpuhp_kick_ap_work(cpu);
1710                 /*
1711                  * The AP side has done the error rollback already. Just
1712                  * return the error code..
1713                  */
1714                 if (ret)
1715                         goto out;
1716         }
1717
1718         /*
1719          * Try to reach the target state. We max out on the BP at
1720          * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1721          * responsible for bringing it up to the target state.
1722          */
1723         target = min((int)target, CPUHP_BRINGUP_CPU);
1724         ret = cpuhp_up_callbacks(cpu, st, target);
1725 out:
1726         cpus_write_unlock();
1727         arch_smt_update();
1728         cpu_up_down_serialize_trainwrecks(tasks_frozen);
1729         return ret;
1730 }
1731
1732 static int cpu_up(unsigned int cpu, enum cpuhp_state target)
1733 {
1734         int err = 0;
1735
1736         if (!cpu_possible(cpu)) {
1737                 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1738                        cpu);
1739 #if defined(CONFIG_IA64)
1740                 pr_err("please check additional_cpus= boot parameter\n");
1741 #endif
1742                 return -EINVAL;
1743         }
1744
1745         err = try_online_node(cpu_to_node(cpu));
1746         if (err)
1747                 return err;
1748
1749         cpu_maps_update_begin();
1750
1751         if (cpu_hotplug_disabled) {
1752                 err = -EBUSY;
1753                 goto out;
1754         }
1755         if (!cpu_bootable(cpu)) {
1756                 err = -EPERM;
1757                 goto out;
1758         }
1759
1760         err = _cpu_up(cpu, 0, target);
1761 out:
1762         cpu_maps_update_done();
1763         return err;
1764 }
1765
1766 /**
1767  * cpu_device_up - Bring up a cpu device
1768  * @dev: Pointer to the cpu device to online
1769  *
1770  * This function is meant to be used by device core cpu subsystem only.
1771  *
1772  * Other subsystems should use add_cpu() instead.
1773  *
1774  * Return: %0 on success or a negative errno code
1775  */
1776 int cpu_device_up(struct device *dev)
1777 {
1778         return cpu_up(dev->id, CPUHP_ONLINE);
1779 }
1780
1781 int add_cpu(unsigned int cpu)
1782 {
1783         int ret;
1784
1785         lock_device_hotplug();
1786         ret = device_online(get_cpu_device(cpu));
1787         unlock_device_hotplug();
1788
1789         return ret;
1790 }
1791 EXPORT_SYMBOL_GPL(add_cpu);
1792
1793 /**
1794  * bringup_hibernate_cpu - Bring up the CPU that we hibernated on
1795  * @sleep_cpu: The cpu we hibernated on and should be brought up.
1796  *
1797  * On some architectures like arm64, we can hibernate on any CPU, but on
1798  * wake up the CPU we hibernated on might be offline as a side effect of
1799  * using maxcpus= for example.
1800  *
1801  * Return: %0 on success or a negative errno code
1802  */
1803 int bringup_hibernate_cpu(unsigned int sleep_cpu)
1804 {
1805         int ret;
1806
1807         if (!cpu_online(sleep_cpu)) {
1808                 pr_info("Hibernated on a CPU that is offline! Bringing CPU up.\n");
1809                 ret = cpu_up(sleep_cpu, CPUHP_ONLINE);
1810                 if (ret) {
1811                         pr_err("Failed to bring hibernate-CPU up!\n");
1812                         return ret;
1813                 }
1814         }
1815         return 0;
1816 }
1817
1818 static void __init cpuhp_bringup_mask(const struct cpumask *mask, unsigned int ncpus,
1819                                       enum cpuhp_state target)
1820 {
1821         unsigned int cpu;
1822
1823         for_each_cpu(cpu, mask) {
1824                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1825
1826                 if (cpu_up(cpu, target) && can_rollback_cpu(st)) {
1827                         /*
1828                          * If this failed then cpu_up() might have only
1829                          * rolled back to CPUHP_BP_KICK_AP for the final
1830                          * online. Clean it up. NOOP if already rolled back.
1831                          */
1832                         WARN_ON(cpuhp_invoke_callback_range(false, cpu, st, CPUHP_OFFLINE));
1833                 }
1834
1835                 if (!--ncpus)
1836                         break;
1837         }
1838 }
1839
1840 #ifdef CONFIG_HOTPLUG_PARALLEL
1841 static bool __cpuhp_parallel_bringup __ro_after_init = true;
1842
1843 static int __init parallel_bringup_parse_param(char *arg)
1844 {
1845         return kstrtobool(arg, &__cpuhp_parallel_bringup);
1846 }
1847 early_param("cpuhp.parallel", parallel_bringup_parse_param);
1848
1849 static inline bool cpuhp_smt_aware(void)
1850 {
1851         return cpu_smt_max_threads > 1;
1852 }
1853
1854 static inline const struct cpumask *cpuhp_get_primary_thread_mask(void)
1855 {
1856         return cpu_primary_thread_mask;
1857 }
1858
1859 /*
1860  * On architectures which have enabled parallel bringup this invokes all BP
1861  * prepare states for each of the to be onlined APs first. The last state
1862  * sends the startup IPI to the APs. The APs proceed through the low level
1863  * bringup code in parallel and then wait for the control CPU to release
1864  * them one by one for the final onlining procedure.
1865  *
1866  * This avoids waiting for each AP to respond to the startup IPI in
1867  * CPUHP_BRINGUP_CPU.
1868  */
1869 static bool __init cpuhp_bringup_cpus_parallel(unsigned int ncpus)
1870 {
1871         const struct cpumask *mask = cpu_present_mask;
1872
1873         if (__cpuhp_parallel_bringup)
1874                 __cpuhp_parallel_bringup = arch_cpuhp_init_parallel_bringup();
1875         if (!__cpuhp_parallel_bringup)
1876                 return false;
1877
1878         if (cpuhp_smt_aware()) {
1879                 const struct cpumask *pmask = cpuhp_get_primary_thread_mask();
1880                 static struct cpumask tmp_mask __initdata;
1881
1882                 /*
1883                  * X86 requires to prevent that SMT siblings stopped while
1884                  * the primary thread does a microcode update for various
1885                  * reasons. Bring the primary threads up first.
1886                  */
1887                 cpumask_and(&tmp_mask, mask, pmask);
1888                 cpuhp_bringup_mask(&tmp_mask, ncpus, CPUHP_BP_KICK_AP);
1889                 cpuhp_bringup_mask(&tmp_mask, ncpus, CPUHP_ONLINE);
1890                 /* Account for the online CPUs */
1891                 ncpus -= num_online_cpus();
1892                 if (!ncpus)
1893                         return true;
1894                 /* Create the mask for secondary CPUs */
1895                 cpumask_andnot(&tmp_mask, mask, pmask);
1896                 mask = &tmp_mask;
1897         }
1898
1899         /* Bring the not-yet started CPUs up */
1900         cpuhp_bringup_mask(mask, ncpus, CPUHP_BP_KICK_AP);
1901         cpuhp_bringup_mask(mask, ncpus, CPUHP_ONLINE);
1902         return true;
1903 }
1904 #else
1905 static inline bool cpuhp_bringup_cpus_parallel(unsigned int ncpus) { return false; }
1906 #endif /* CONFIG_HOTPLUG_PARALLEL */
1907
1908 void __init bringup_nonboot_cpus(unsigned int setup_max_cpus)
1909 {
1910         /* Try parallel bringup optimization if enabled */
1911         if (cpuhp_bringup_cpus_parallel(setup_max_cpus))
1912                 return;
1913
1914         /* Full per CPU serialized bringup */
1915         cpuhp_bringup_mask(cpu_present_mask, setup_max_cpus, CPUHP_ONLINE);
1916 }
1917
1918 #ifdef CONFIG_PM_SLEEP_SMP
1919 static cpumask_var_t frozen_cpus;
1920
1921 int freeze_secondary_cpus(int primary)
1922 {
1923         int cpu, error = 0;
1924
1925         cpu_maps_update_begin();
1926         if (primary == -1) {
1927                 primary = cpumask_first(cpu_online_mask);
1928                 if (!housekeeping_cpu(primary, HK_TYPE_TIMER))
1929                         primary = housekeeping_any_cpu(HK_TYPE_TIMER);
1930         } else {
1931                 if (!cpu_online(primary))
1932                         primary = cpumask_first(cpu_online_mask);
1933         }
1934
1935         /*
1936          * We take down all of the non-boot CPUs in one shot to avoid races
1937          * with the userspace trying to use the CPU hotplug at the same time
1938          */
1939         cpumask_clear(frozen_cpus);
1940
1941         pr_info("Disabling non-boot CPUs ...\n");
1942         for_each_online_cpu(cpu) {
1943                 if (cpu == primary)
1944                         continue;
1945
1946                 if (pm_wakeup_pending()) {
1947                         pr_info("Wakeup pending. Abort CPU freeze\n");
1948                         error = -EBUSY;
1949                         break;
1950                 }
1951
1952                 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1953                 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1954                 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1955                 if (!error)
1956                         cpumask_set_cpu(cpu, frozen_cpus);
1957                 else {
1958                         pr_err("Error taking CPU%d down: %d\n", cpu, error);
1959                         break;
1960                 }
1961         }
1962
1963         if (!error)
1964                 BUG_ON(num_online_cpus() > 1);
1965         else
1966                 pr_err("Non-boot CPUs are not disabled\n");
1967
1968         /*
1969          * Make sure the CPUs won't be enabled by someone else. We need to do
1970          * this even in case of failure as all freeze_secondary_cpus() users are
1971          * supposed to do thaw_secondary_cpus() on the failure path.
1972          */
1973         cpu_hotplug_disabled++;
1974
1975         cpu_maps_update_done();
1976         return error;
1977 }
1978
1979 void __weak arch_thaw_secondary_cpus_begin(void)
1980 {
1981 }
1982
1983 void __weak arch_thaw_secondary_cpus_end(void)
1984 {
1985 }
1986
1987 void thaw_secondary_cpus(void)
1988 {
1989         int cpu, error;
1990
1991         /* Allow everyone to use the CPU hotplug again */
1992         cpu_maps_update_begin();
1993         __cpu_hotplug_enable();
1994         if (cpumask_empty(frozen_cpus))
1995                 goto out;
1996
1997         pr_info("Enabling non-boot CPUs ...\n");
1998
1999         arch_thaw_secondary_cpus_begin();
2000
2001         for_each_cpu(cpu, frozen_cpus) {
2002                 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
2003                 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
2004                 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
2005                 if (!error) {
2006                         pr_info("CPU%d is up\n", cpu);
2007                         continue;
2008                 }
2009                 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
2010         }
2011
2012         arch_thaw_secondary_cpus_end();
2013
2014         cpumask_clear(frozen_cpus);
2015 out:
2016         cpu_maps_update_done();
2017 }
2018
2019 static int __init alloc_frozen_cpus(void)
2020 {
2021         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
2022                 return -ENOMEM;
2023         return 0;
2024 }
2025 core_initcall(alloc_frozen_cpus);
2026
2027 /*
2028  * When callbacks for CPU hotplug notifications are being executed, we must
2029  * ensure that the state of the system with respect to the tasks being frozen
2030  * or not, as reported by the notification, remains unchanged *throughout the
2031  * duration* of the execution of the callbacks.
2032  * Hence we need to prevent the freezer from racing with regular CPU hotplug.
2033  *
2034  * This synchronization is implemented by mutually excluding regular CPU
2035  * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
2036  * Hibernate notifications.
2037  */
2038 static int
2039 cpu_hotplug_pm_callback(struct notifier_block *nb,
2040                         unsigned long action, void *ptr)
2041 {
2042         switch (action) {
2043
2044         case PM_SUSPEND_PREPARE:
2045         case PM_HIBERNATION_PREPARE:
2046                 cpu_hotplug_disable();
2047                 break;
2048
2049         case PM_POST_SUSPEND:
2050         case PM_POST_HIBERNATION:
2051                 cpu_hotplug_enable();
2052                 break;
2053
2054         default:
2055                 return NOTIFY_DONE;
2056         }
2057
2058         return NOTIFY_OK;
2059 }
2060
2061
2062 static int __init cpu_hotplug_pm_sync_init(void)
2063 {
2064         /*
2065          * cpu_hotplug_pm_callback has higher priority than x86
2066          * bsp_pm_callback which depends on cpu_hotplug_pm_callback
2067          * to disable cpu hotplug to avoid cpu hotplug race.
2068          */
2069         pm_notifier(cpu_hotplug_pm_callback, 0);
2070         return 0;
2071 }
2072 core_initcall(cpu_hotplug_pm_sync_init);
2073
2074 #endif /* CONFIG_PM_SLEEP_SMP */
2075
2076 int __boot_cpu_id;
2077
2078 #endif /* CONFIG_SMP */
2079
2080 /* Boot processor state steps */
2081 static struct cpuhp_step cpuhp_hp_states[] = {
2082         [CPUHP_OFFLINE] = {
2083                 .name                   = "offline",
2084                 .startup.single         = NULL,
2085                 .teardown.single        = NULL,
2086         },
2087 #ifdef CONFIG_SMP
2088         [CPUHP_CREATE_THREADS]= {
2089                 .name                   = "threads:prepare",
2090                 .startup.single         = smpboot_create_threads,
2091                 .teardown.single        = NULL,
2092                 .cant_stop              = true,
2093         },
2094         [CPUHP_PERF_PREPARE] = {
2095                 .name                   = "perf:prepare",
2096                 .startup.single         = perf_event_init_cpu,
2097                 .teardown.single        = perf_event_exit_cpu,
2098         },
2099         [CPUHP_RANDOM_PREPARE] = {
2100                 .name                   = "random:prepare",
2101                 .startup.single         = random_prepare_cpu,
2102                 .teardown.single        = NULL,
2103         },
2104         [CPUHP_WORKQUEUE_PREP] = {
2105                 .name                   = "workqueue:prepare",
2106                 .startup.single         = workqueue_prepare_cpu,
2107                 .teardown.single        = NULL,
2108         },
2109         [CPUHP_HRTIMERS_PREPARE] = {
2110                 .name                   = "hrtimers:prepare",
2111                 .startup.single         = hrtimers_prepare_cpu,
2112                 .teardown.single        = NULL,
2113         },
2114         [CPUHP_SMPCFD_PREPARE] = {
2115                 .name                   = "smpcfd:prepare",
2116                 .startup.single         = smpcfd_prepare_cpu,
2117                 .teardown.single        = smpcfd_dead_cpu,
2118         },
2119         [CPUHP_RELAY_PREPARE] = {
2120                 .name                   = "relay:prepare",
2121                 .startup.single         = relay_prepare_cpu,
2122                 .teardown.single        = NULL,
2123         },
2124         [CPUHP_SLAB_PREPARE] = {
2125                 .name                   = "slab:prepare",
2126                 .startup.single         = slab_prepare_cpu,
2127                 .teardown.single        = slab_dead_cpu,
2128         },
2129         [CPUHP_RCUTREE_PREP] = {
2130                 .name                   = "RCU/tree:prepare",
2131                 .startup.single         = rcutree_prepare_cpu,
2132                 .teardown.single        = rcutree_dead_cpu,
2133         },
2134         /*
2135          * On the tear-down path, timers_dead_cpu() must be invoked
2136          * before blk_mq_queue_reinit_notify() from notify_dead(),
2137          * otherwise a RCU stall occurs.
2138          */
2139         [CPUHP_TIMERS_PREPARE] = {
2140                 .name                   = "timers:prepare",
2141                 .startup.single         = timers_prepare_cpu,
2142                 .teardown.single        = timers_dead_cpu,
2143         },
2144
2145 #ifdef CONFIG_HOTPLUG_SPLIT_STARTUP
2146         /*
2147          * Kicks the AP alive. AP will wait in cpuhp_ap_sync_alive() until
2148          * the next step will release it.
2149          */
2150         [CPUHP_BP_KICK_AP] = {
2151                 .name                   = "cpu:kick_ap",
2152                 .startup.single         = cpuhp_kick_ap_alive,
2153         },
2154
2155         /*
2156          * Waits for the AP to reach cpuhp_ap_sync_alive() and then
2157          * releases it for the complete bringup.
2158          */
2159         [CPUHP_BRINGUP_CPU] = {
2160                 .name                   = "cpu:bringup",
2161                 .startup.single         = cpuhp_bringup_ap,
2162                 .teardown.single        = finish_cpu,
2163                 .cant_stop              = true,
2164         },
2165 #else
2166         /*
2167          * All-in-one CPU bringup state which includes the kick alive.
2168          */
2169         [CPUHP_BRINGUP_CPU] = {
2170                 .name                   = "cpu:bringup",
2171                 .startup.single         = bringup_cpu,
2172                 .teardown.single        = finish_cpu,
2173                 .cant_stop              = true,
2174         },
2175 #endif
2176         /* Final state before CPU kills itself */
2177         [CPUHP_AP_IDLE_DEAD] = {
2178                 .name                   = "idle:dead",
2179         },
2180         /*
2181          * Last state before CPU enters the idle loop to die. Transient state
2182          * for synchronization.
2183          */
2184         [CPUHP_AP_OFFLINE] = {
2185                 .name                   = "ap:offline",
2186                 .cant_stop              = true,
2187         },
2188         /* First state is scheduler control. Interrupts are disabled */
2189         [CPUHP_AP_SCHED_STARTING] = {
2190                 .name                   = "sched:starting",
2191                 .startup.single         = sched_cpu_starting,
2192                 .teardown.single        = sched_cpu_dying,
2193         },
2194         [CPUHP_AP_RCUTREE_DYING] = {
2195                 .name                   = "RCU/tree:dying",
2196                 .startup.single         = NULL,
2197                 .teardown.single        = rcutree_dying_cpu,
2198         },
2199         [CPUHP_AP_SMPCFD_DYING] = {
2200                 .name                   = "smpcfd:dying",
2201                 .startup.single         = NULL,
2202                 .teardown.single        = smpcfd_dying_cpu,
2203         },
2204         [CPUHP_AP_HRTIMERS_DYING] = {
2205                 .name                   = "hrtimers:dying",
2206                 .startup.single         = NULL,
2207                 .teardown.single        = hrtimers_cpu_dying,
2208         },
2209
2210         /* Entry state on starting. Interrupts enabled from here on. Transient
2211          * state for synchronsization */
2212         [CPUHP_AP_ONLINE] = {
2213                 .name                   = "ap:online",
2214         },
2215         /*
2216          * Handled on control processor until the plugged processor manages
2217          * this itself.
2218          */
2219         [CPUHP_TEARDOWN_CPU] = {
2220                 .name                   = "cpu:teardown",
2221                 .startup.single         = NULL,
2222                 .teardown.single        = takedown_cpu,
2223                 .cant_stop              = true,
2224         },
2225
2226         [CPUHP_AP_SCHED_WAIT_EMPTY] = {
2227                 .name                   = "sched:waitempty",
2228                 .startup.single         = NULL,
2229                 .teardown.single        = sched_cpu_wait_empty,
2230         },
2231
2232         /* Handle smpboot threads park/unpark */
2233         [CPUHP_AP_SMPBOOT_THREADS] = {
2234                 .name                   = "smpboot/threads:online",
2235                 .startup.single         = smpboot_unpark_threads,
2236                 .teardown.single        = smpboot_park_threads,
2237         },
2238         [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
2239                 .name                   = "irq/affinity:online",
2240                 .startup.single         = irq_affinity_online_cpu,
2241                 .teardown.single        = NULL,
2242         },
2243         [CPUHP_AP_PERF_ONLINE] = {
2244                 .name                   = "perf:online",
2245                 .startup.single         = perf_event_init_cpu,
2246                 .teardown.single        = perf_event_exit_cpu,
2247         },
2248         [CPUHP_AP_WATCHDOG_ONLINE] = {
2249                 .name                   = "lockup_detector:online",
2250                 .startup.single         = lockup_detector_online_cpu,
2251                 .teardown.single        = lockup_detector_offline_cpu,
2252         },
2253         [CPUHP_AP_WORKQUEUE_ONLINE] = {
2254                 .name                   = "workqueue:online",
2255                 .startup.single         = workqueue_online_cpu,
2256                 .teardown.single        = workqueue_offline_cpu,
2257         },
2258         [CPUHP_AP_RANDOM_ONLINE] = {
2259                 .name                   = "random:online",
2260                 .startup.single         = random_online_cpu,
2261                 .teardown.single        = NULL,
2262         },
2263         [CPUHP_AP_RCUTREE_ONLINE] = {
2264                 .name                   = "RCU/tree:online",
2265                 .startup.single         = rcutree_online_cpu,
2266                 .teardown.single        = rcutree_offline_cpu,
2267         },
2268 #endif
2269         /*
2270          * The dynamically registered state space is here
2271          */
2272
2273 #ifdef CONFIG_SMP
2274         /* Last state is scheduler control setting the cpu active */
2275         [CPUHP_AP_ACTIVE] = {
2276                 .name                   = "sched:active",
2277                 .startup.single         = sched_cpu_activate,
2278                 .teardown.single        = sched_cpu_deactivate,
2279         },
2280 #endif
2281
2282         /* CPU is fully up and running. */
2283         [CPUHP_ONLINE] = {
2284                 .name                   = "online",
2285                 .startup.single         = NULL,
2286                 .teardown.single        = NULL,
2287         },
2288 };
2289
2290 /* Sanity check for callbacks */
2291 static int cpuhp_cb_check(enum cpuhp_state state)
2292 {
2293         if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
2294                 return -EINVAL;
2295         return 0;
2296 }
2297
2298 /*
2299  * Returns a free for dynamic slot assignment of the Online state. The states
2300  * are protected by the cpuhp_slot_states mutex and an empty slot is identified
2301  * by having no name assigned.
2302  */
2303 static int cpuhp_reserve_state(enum cpuhp_state state)
2304 {
2305         enum cpuhp_state i, end;
2306         struct cpuhp_step *step;
2307
2308         switch (state) {
2309         case CPUHP_AP_ONLINE_DYN:
2310                 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
2311                 end = CPUHP_AP_ONLINE_DYN_END;
2312                 break;
2313         case CPUHP_BP_PREPARE_DYN:
2314                 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
2315                 end = CPUHP_BP_PREPARE_DYN_END;
2316                 break;
2317         default:
2318                 return -EINVAL;
2319         }
2320
2321         for (i = state; i <= end; i++, step++) {
2322                 if (!step->name)
2323                         return i;
2324         }
2325         WARN(1, "No more dynamic states available for CPU hotplug\n");
2326         return -ENOSPC;
2327 }
2328
2329 static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
2330                                  int (*startup)(unsigned int cpu),
2331                                  int (*teardown)(unsigned int cpu),
2332                                  bool multi_instance)
2333 {
2334         /* (Un)Install the callbacks for further cpu hotplug operations */
2335         struct cpuhp_step *sp;
2336         int ret = 0;
2337
2338         /*
2339          * If name is NULL, then the state gets removed.
2340          *
2341          * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
2342          * the first allocation from these dynamic ranges, so the removal
2343          * would trigger a new allocation and clear the wrong (already
2344          * empty) state, leaving the callbacks of the to be cleared state
2345          * dangling, which causes wreckage on the next hotplug operation.
2346          */
2347         if (name && (state == CPUHP_AP_ONLINE_DYN ||
2348                      state == CPUHP_BP_PREPARE_DYN)) {
2349                 ret = cpuhp_reserve_state(state);
2350                 if (ret < 0)
2351                         return ret;
2352                 state = ret;
2353         }
2354         sp = cpuhp_get_step(state);
2355         if (name && sp->name)
2356                 return -EBUSY;
2357
2358         sp->startup.single = startup;
2359         sp->teardown.single = teardown;
2360         sp->name = name;
2361         sp->multi_instance = multi_instance;
2362         INIT_HLIST_HEAD(&sp->list);
2363         return ret;
2364 }
2365
2366 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
2367 {
2368         return cpuhp_get_step(state)->teardown.single;
2369 }
2370
2371 /*
2372  * Call the startup/teardown function for a step either on the AP or
2373  * on the current CPU.
2374  */
2375 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
2376                             struct hlist_node *node)
2377 {
2378         struct cpuhp_step *sp = cpuhp_get_step(state);
2379         int ret;
2380
2381         /*
2382          * If there's nothing to do, we done.
2383          * Relies on the union for multi_instance.
2384          */
2385         if (cpuhp_step_empty(bringup, sp))
2386                 return 0;
2387         /*
2388          * The non AP bound callbacks can fail on bringup. On teardown
2389          * e.g. module removal we crash for now.
2390          */
2391 #ifdef CONFIG_SMP
2392         if (cpuhp_is_ap_state(state))
2393                 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
2394         else
2395                 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
2396 #else
2397         ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
2398 #endif
2399         BUG_ON(ret && !bringup);
2400         return ret;
2401 }
2402
2403 /*
2404  * Called from __cpuhp_setup_state on a recoverable failure.
2405  *
2406  * Note: The teardown callbacks for rollback are not allowed to fail!
2407  */
2408 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
2409                                    struct hlist_node *node)
2410 {
2411         int cpu;
2412
2413         /* Roll back the already executed steps on the other cpus */
2414         for_each_present_cpu(cpu) {
2415                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2416                 int cpustate = st->state;
2417
2418                 if (cpu >= failedcpu)
2419                         break;
2420
2421                 /* Did we invoke the startup call on that cpu ? */
2422                 if (cpustate >= state)
2423                         cpuhp_issue_call(cpu, state, false, node);
2424         }
2425 }
2426
2427 int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
2428                                           struct hlist_node *node,
2429                                           bool invoke)
2430 {
2431         struct cpuhp_step *sp;
2432         int cpu;
2433         int ret;
2434
2435         lockdep_assert_cpus_held();
2436
2437         sp = cpuhp_get_step(state);
2438         if (sp->multi_instance == false)
2439                 return -EINVAL;
2440
2441         mutex_lock(&cpuhp_state_mutex);
2442
2443         if (!invoke || !sp->startup.multi)
2444                 goto add_node;
2445
2446         /*
2447          * Try to call the startup callback for each present cpu
2448          * depending on the hotplug state of the cpu.
2449          */
2450         for_each_present_cpu(cpu) {
2451                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2452                 int cpustate = st->state;
2453
2454                 if (cpustate < state)
2455                         continue;
2456
2457                 ret = cpuhp_issue_call(cpu, state, true, node);
2458                 if (ret) {
2459                         if (sp->teardown.multi)
2460                                 cpuhp_rollback_install(cpu, state, node);
2461                         goto unlock;
2462                 }
2463         }
2464 add_node:
2465         ret = 0;
2466         hlist_add_head(node, &sp->list);
2467 unlock:
2468         mutex_unlock(&cpuhp_state_mutex);
2469         return ret;
2470 }
2471
2472 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
2473                                bool invoke)
2474 {
2475         int ret;
2476
2477         cpus_read_lock();
2478         ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
2479         cpus_read_unlock();
2480         return ret;
2481 }
2482 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
2483
2484 /**
2485  * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
2486  * @state:              The state to setup
2487  * @name:               Name of the step
2488  * @invoke:             If true, the startup function is invoked for cpus where
2489  *                      cpu state >= @state
2490  * @startup:            startup callback function
2491  * @teardown:           teardown callback function
2492  * @multi_instance:     State is set up for multiple instances which get
2493  *                      added afterwards.
2494  *
2495  * The caller needs to hold cpus read locked while calling this function.
2496  * Return:
2497  *   On success:
2498  *      Positive state number if @state is CPUHP_AP_ONLINE_DYN;
2499  *      0 for all other states
2500  *   On failure: proper (negative) error code
2501  */
2502 int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
2503                                    const char *name, bool invoke,
2504                                    int (*startup)(unsigned int cpu),
2505                                    int (*teardown)(unsigned int cpu),
2506                                    bool multi_instance)
2507 {
2508         int cpu, ret = 0;
2509         bool dynstate;
2510
2511         lockdep_assert_cpus_held();
2512
2513         if (cpuhp_cb_check(state) || !name)
2514                 return -EINVAL;
2515
2516         mutex_lock(&cpuhp_state_mutex);
2517
2518         ret = cpuhp_store_callbacks(state, name, startup, teardown,
2519                                     multi_instance);
2520
2521         dynstate = state == CPUHP_AP_ONLINE_DYN;
2522         if (ret > 0 && dynstate) {
2523                 state = ret;
2524                 ret = 0;
2525         }
2526
2527         if (ret || !invoke || !startup)
2528                 goto out;
2529
2530         /*
2531          * Try to call the startup callback for each present cpu
2532          * depending on the hotplug state of the cpu.
2533          */
2534         for_each_present_cpu(cpu) {
2535                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2536                 int cpustate = st->state;
2537
2538                 if (cpustate < state)
2539                         continue;
2540
2541                 ret = cpuhp_issue_call(cpu, state, true, NULL);
2542                 if (ret) {
2543                         if (teardown)
2544                                 cpuhp_rollback_install(cpu, state, NULL);
2545                         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2546                         goto out;
2547                 }
2548         }
2549 out:
2550         mutex_unlock(&cpuhp_state_mutex);
2551         /*
2552          * If the requested state is CPUHP_AP_ONLINE_DYN, return the
2553          * dynamically allocated state in case of success.
2554          */
2555         if (!ret && dynstate)
2556                 return state;
2557         return ret;
2558 }
2559 EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
2560
2561 int __cpuhp_setup_state(enum cpuhp_state state,
2562                         const char *name, bool invoke,
2563                         int (*startup)(unsigned int cpu),
2564                         int (*teardown)(unsigned int cpu),
2565                         bool multi_instance)
2566 {
2567         int ret;
2568
2569         cpus_read_lock();
2570         ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
2571                                              teardown, multi_instance);
2572         cpus_read_unlock();
2573         return ret;
2574 }
2575 EXPORT_SYMBOL(__cpuhp_setup_state);
2576
2577 int __cpuhp_state_remove_instance(enum cpuhp_state state,
2578                                   struct hlist_node *node, bool invoke)
2579 {
2580         struct cpuhp_step *sp = cpuhp_get_step(state);
2581         int cpu;
2582
2583         BUG_ON(cpuhp_cb_check(state));
2584
2585         if (!sp->multi_instance)
2586                 return -EINVAL;
2587
2588         cpus_read_lock();
2589         mutex_lock(&cpuhp_state_mutex);
2590
2591         if (!invoke || !cpuhp_get_teardown_cb(state))
2592                 goto remove;
2593         /*
2594          * Call the teardown callback for each present cpu depending
2595          * on the hotplug state of the cpu. This function is not
2596          * allowed to fail currently!
2597          */
2598         for_each_present_cpu(cpu) {
2599                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2600                 int cpustate = st->state;
2601
2602                 if (cpustate >= state)
2603                         cpuhp_issue_call(cpu, state, false, node);
2604         }
2605
2606 remove:
2607         hlist_del(node);
2608         mutex_unlock(&cpuhp_state_mutex);
2609         cpus_read_unlock();
2610
2611         return 0;
2612 }
2613 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
2614
2615 /**
2616  * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
2617  * @state:      The state to remove
2618  * @invoke:     If true, the teardown function is invoked for cpus where
2619  *              cpu state >= @state
2620  *
2621  * The caller needs to hold cpus read locked while calling this function.
2622  * The teardown callback is currently not allowed to fail. Think
2623  * about module removal!
2624  */
2625 void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
2626 {
2627         struct cpuhp_step *sp = cpuhp_get_step(state);
2628         int cpu;
2629
2630         BUG_ON(cpuhp_cb_check(state));
2631
2632         lockdep_assert_cpus_held();
2633
2634         mutex_lock(&cpuhp_state_mutex);
2635         if (sp->multi_instance) {
2636                 WARN(!hlist_empty(&sp->list),
2637                      "Error: Removing state %d which has instances left.\n",
2638                      state);
2639                 goto remove;
2640         }
2641
2642         if (!invoke || !cpuhp_get_teardown_cb(state))
2643                 goto remove;
2644
2645         /*
2646          * Call the teardown callback for each present cpu depending
2647          * on the hotplug state of the cpu. This function is not
2648          * allowed to fail currently!
2649          */
2650         for_each_present_cpu(cpu) {
2651                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
2652                 int cpustate = st->state;
2653
2654                 if (cpustate >= state)
2655                         cpuhp_issue_call(cpu, state, false, NULL);
2656         }
2657 remove:
2658         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
2659         mutex_unlock(&cpuhp_state_mutex);
2660 }
2661 EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
2662
2663 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
2664 {
2665         cpus_read_lock();
2666         __cpuhp_remove_state_cpuslocked(state, invoke);
2667         cpus_read_unlock();
2668 }
2669 EXPORT_SYMBOL(__cpuhp_remove_state);
2670
2671 #ifdef CONFIG_HOTPLUG_SMT
2672 static void cpuhp_offline_cpu_device(unsigned int cpu)
2673 {
2674         struct device *dev = get_cpu_device(cpu);
2675
2676         dev->offline = true;
2677         /* Tell user space about the state change */
2678         kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
2679 }
2680
2681 static void cpuhp_online_cpu_device(unsigned int cpu)
2682 {
2683         struct device *dev = get_cpu_device(cpu);
2684
2685         dev->offline = false;
2686         /* Tell user space about the state change */
2687         kobject_uevent(&dev->kobj, KOBJ_ONLINE);
2688 }
2689
2690 int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
2691 {
2692         int cpu, ret = 0;
2693
2694         cpu_maps_update_begin();
2695         for_each_online_cpu(cpu) {
2696                 if (topology_is_primary_thread(cpu))
2697                         continue;
2698                 /*
2699                  * Disable can be called with CPU_SMT_ENABLED when changing
2700                  * from a higher to lower number of SMT threads per core.
2701                  */
2702                 if (ctrlval == CPU_SMT_ENABLED && cpu_smt_thread_allowed(cpu))
2703                         continue;
2704                 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
2705                 if (ret)
2706                         break;
2707                 /*
2708                  * As this needs to hold the cpu maps lock it's impossible
2709                  * to call device_offline() because that ends up calling
2710                  * cpu_down() which takes cpu maps lock. cpu maps lock
2711                  * needs to be held as this might race against in kernel
2712                  * abusers of the hotplug machinery (thermal management).
2713                  *
2714                  * So nothing would update device:offline state. That would
2715                  * leave the sysfs entry stale and prevent onlining after
2716                  * smt control has been changed to 'off' again. This is
2717                  * called under the sysfs hotplug lock, so it is properly
2718                  * serialized against the regular offline usage.
2719                  */
2720                 cpuhp_offline_cpu_device(cpu);
2721         }
2722         if (!ret)
2723                 cpu_smt_control = ctrlval;
2724         cpu_maps_update_done();
2725         return ret;
2726 }
2727
2728 int cpuhp_smt_enable(void)
2729 {
2730         int cpu, ret = 0;
2731
2732         cpu_maps_update_begin();
2733         cpu_smt_control = CPU_SMT_ENABLED;
2734         for_each_present_cpu(cpu) {
2735                 /* Skip online CPUs and CPUs on offline nodes */
2736                 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
2737                         continue;
2738                 if (!cpu_smt_thread_allowed(cpu))
2739                         continue;
2740                 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
2741                 if (ret)
2742                         break;
2743                 /* See comment in cpuhp_smt_disable() */
2744                 cpuhp_online_cpu_device(cpu);
2745         }
2746         cpu_maps_update_done();
2747         return ret;
2748 }
2749 #endif
2750
2751 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
2752 static ssize_t state_show(struct device *dev,
2753                           struct device_attribute *attr, char *buf)
2754 {
2755         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2756
2757         return sprintf(buf, "%d\n", st->state);
2758 }
2759 static DEVICE_ATTR_RO(state);
2760
2761 static ssize_t target_store(struct device *dev, struct device_attribute *attr,
2762                             const char *buf, size_t count)
2763 {
2764         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2765         struct cpuhp_step *sp;
2766         int target, ret;
2767
2768         ret = kstrtoint(buf, 10, &target);
2769         if (ret)
2770                 return ret;
2771
2772 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2773         if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2774                 return -EINVAL;
2775 #else
2776         if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2777                 return -EINVAL;
2778 #endif
2779
2780         ret = lock_device_hotplug_sysfs();
2781         if (ret)
2782                 return ret;
2783
2784         mutex_lock(&cpuhp_state_mutex);
2785         sp = cpuhp_get_step(target);
2786         ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2787         mutex_unlock(&cpuhp_state_mutex);
2788         if (ret)
2789                 goto out;
2790
2791         if (st->state < target)
2792                 ret = cpu_up(dev->id, target);
2793         else if (st->state > target)
2794                 ret = cpu_down(dev->id, target);
2795         else if (WARN_ON(st->target != target))
2796                 st->target = target;
2797 out:
2798         unlock_device_hotplug();
2799         return ret ? ret : count;
2800 }
2801
2802 static ssize_t target_show(struct device *dev,
2803                            struct device_attribute *attr, char *buf)
2804 {
2805         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2806
2807         return sprintf(buf, "%d\n", st->target);
2808 }
2809 static DEVICE_ATTR_RW(target);
2810
2811 static ssize_t fail_store(struct device *dev, struct device_attribute *attr,
2812                           const char *buf, size_t count)
2813 {
2814         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2815         struct cpuhp_step *sp;
2816         int fail, ret;
2817
2818         ret = kstrtoint(buf, 10, &fail);
2819         if (ret)
2820                 return ret;
2821
2822         if (fail == CPUHP_INVALID) {
2823                 st->fail = fail;
2824                 return count;
2825         }
2826
2827         if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2828                 return -EINVAL;
2829
2830         /*
2831          * Cannot fail STARTING/DYING callbacks.
2832          */
2833         if (cpuhp_is_atomic_state(fail))
2834                 return -EINVAL;
2835
2836         /*
2837          * DEAD callbacks cannot fail...
2838          * ... neither can CPUHP_BRINGUP_CPU during hotunplug. The latter
2839          * triggering STARTING callbacks, a failure in this state would
2840          * hinder rollback.
2841          */
2842         if (fail <= CPUHP_BRINGUP_CPU && st->state > CPUHP_BRINGUP_CPU)
2843                 return -EINVAL;
2844
2845         /*
2846          * Cannot fail anything that doesn't have callbacks.
2847          */
2848         mutex_lock(&cpuhp_state_mutex);
2849         sp = cpuhp_get_step(fail);
2850         if (!sp->startup.single && !sp->teardown.single)
2851                 ret = -EINVAL;
2852         mutex_unlock(&cpuhp_state_mutex);
2853         if (ret)
2854                 return ret;
2855
2856         st->fail = fail;
2857
2858         return count;
2859 }
2860
2861 static ssize_t fail_show(struct device *dev,
2862                          struct device_attribute *attr, char *buf)
2863 {
2864         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2865
2866         return sprintf(buf, "%d\n", st->fail);
2867 }
2868
2869 static DEVICE_ATTR_RW(fail);
2870
2871 static struct attribute *cpuhp_cpu_attrs[] = {
2872         &dev_attr_state.attr,
2873         &dev_attr_target.attr,
2874         &dev_attr_fail.attr,
2875         NULL
2876 };
2877
2878 static const struct attribute_group cpuhp_cpu_attr_group = {
2879         .attrs = cpuhp_cpu_attrs,
2880         .name = "hotplug",
2881         NULL
2882 };
2883
2884 static ssize_t states_show(struct device *dev,
2885                                  struct device_attribute *attr, char *buf)
2886 {
2887         ssize_t cur, res = 0;
2888         int i;
2889
2890         mutex_lock(&cpuhp_state_mutex);
2891         for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2892                 struct cpuhp_step *sp = cpuhp_get_step(i);
2893
2894                 if (sp->name) {
2895                         cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2896                         buf += cur;
2897                         res += cur;
2898                 }
2899         }
2900         mutex_unlock(&cpuhp_state_mutex);
2901         return res;
2902 }
2903 static DEVICE_ATTR_RO(states);
2904
2905 static struct attribute *cpuhp_cpu_root_attrs[] = {
2906         &dev_attr_states.attr,
2907         NULL
2908 };
2909
2910 static const struct attribute_group cpuhp_cpu_root_attr_group = {
2911         .attrs = cpuhp_cpu_root_attrs,
2912         .name = "hotplug",
2913         NULL
2914 };
2915
2916 #ifdef CONFIG_HOTPLUG_SMT
2917
2918 static bool cpu_smt_num_threads_valid(unsigned int threads)
2919 {
2920         if (IS_ENABLED(CONFIG_SMT_NUM_THREADS_DYNAMIC))
2921                 return threads >= 1 && threads <= cpu_smt_max_threads;
2922         return threads == 1 || threads == cpu_smt_max_threads;
2923 }
2924
2925 static ssize_t
2926 __store_smt_control(struct device *dev, struct device_attribute *attr,
2927                     const char *buf, size_t count)
2928 {
2929         int ctrlval, ret, num_threads, orig_threads;
2930         bool force_off;
2931
2932         if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2933                 return -EPERM;
2934
2935         if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2936                 return -ENODEV;
2937
2938         if (sysfs_streq(buf, "on")) {
2939                 ctrlval = CPU_SMT_ENABLED;
2940                 num_threads = cpu_smt_max_threads;
2941         } else if (sysfs_streq(buf, "off")) {
2942                 ctrlval = CPU_SMT_DISABLED;
2943                 num_threads = 1;
2944         } else if (sysfs_streq(buf, "forceoff")) {
2945                 ctrlval = CPU_SMT_FORCE_DISABLED;
2946                 num_threads = 1;
2947         } else if (kstrtoint(buf, 10, &num_threads) == 0) {
2948                 if (num_threads == 1)
2949                         ctrlval = CPU_SMT_DISABLED;
2950                 else if (cpu_smt_num_threads_valid(num_threads))
2951                         ctrlval = CPU_SMT_ENABLED;
2952                 else
2953                         return -EINVAL;
2954         } else {
2955                 return -EINVAL;
2956         }
2957
2958         ret = lock_device_hotplug_sysfs();
2959         if (ret)
2960                 return ret;
2961
2962         orig_threads = cpu_smt_num_threads;
2963         cpu_smt_num_threads = num_threads;
2964
2965         force_off = ctrlval != cpu_smt_control && ctrlval == CPU_SMT_FORCE_DISABLED;
2966
2967         if (num_threads > orig_threads)
2968                 ret = cpuhp_smt_enable();
2969         else if (num_threads < orig_threads || force_off)
2970                 ret = cpuhp_smt_disable(ctrlval);
2971
2972         unlock_device_hotplug();
2973         return ret ? ret : count;
2974 }
2975
2976 #else /* !CONFIG_HOTPLUG_SMT */
2977 static ssize_t
2978 __store_smt_control(struct device *dev, struct device_attribute *attr,
2979                     const char *buf, size_t count)
2980 {
2981         return -ENODEV;
2982 }
2983 #endif /* CONFIG_HOTPLUG_SMT */
2984
2985 static const char *smt_states[] = {
2986         [CPU_SMT_ENABLED]               = "on",
2987         [CPU_SMT_DISABLED]              = "off",
2988         [CPU_SMT_FORCE_DISABLED]        = "forceoff",
2989         [CPU_SMT_NOT_SUPPORTED]         = "notsupported",
2990         [CPU_SMT_NOT_IMPLEMENTED]       = "notimplemented",
2991 };
2992
2993 static ssize_t control_show(struct device *dev,
2994                             struct device_attribute *attr, char *buf)
2995 {
2996         const char *state = smt_states[cpu_smt_control];
2997
2998 #ifdef CONFIG_HOTPLUG_SMT
2999         /*
3000          * If SMT is enabled but not all threads are enabled then show the
3001          * number of threads. If all threads are enabled show "on". Otherwise
3002          * show the state name.
3003          */
3004         if (cpu_smt_control == CPU_SMT_ENABLED &&
3005             cpu_smt_num_threads != cpu_smt_max_threads)
3006                 return sysfs_emit(buf, "%d\n", cpu_smt_num_threads);
3007 #endif
3008
3009         return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
3010 }
3011
3012 static ssize_t control_store(struct device *dev, struct device_attribute *attr,
3013                              const char *buf, size_t count)
3014 {
3015         return __store_smt_control(dev, attr, buf, count);
3016 }
3017 static DEVICE_ATTR_RW(control);
3018
3019 static ssize_t active_show(struct device *dev,
3020                            struct device_attribute *attr, char *buf)
3021 {
3022         return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
3023 }
3024 static DEVICE_ATTR_RO(active);
3025
3026 static struct attribute *cpuhp_smt_attrs[] = {
3027         &dev_attr_control.attr,
3028         &dev_attr_active.attr,
3029         NULL
3030 };
3031
3032 static const struct attribute_group cpuhp_smt_attr_group = {
3033         .attrs = cpuhp_smt_attrs,
3034         .name = "smt",
3035         NULL
3036 };
3037
3038 static int __init cpu_smt_sysfs_init(void)
3039 {
3040         struct device *dev_root;
3041         int ret = -ENODEV;
3042
3043         dev_root = bus_get_dev_root(&cpu_subsys);
3044         if (dev_root) {
3045                 ret = sysfs_create_group(&dev_root->kobj, &cpuhp_smt_attr_group);
3046                 put_device(dev_root);
3047         }
3048         return ret;
3049 }
3050
3051 static int __init cpuhp_sysfs_init(void)
3052 {
3053         struct device *dev_root;
3054         int cpu, ret;
3055
3056         ret = cpu_smt_sysfs_init();
3057         if (ret)
3058                 return ret;
3059
3060         dev_root = bus_get_dev_root(&cpu_subsys);
3061         if (dev_root) {
3062                 ret = sysfs_create_group(&dev_root->kobj, &cpuhp_cpu_root_attr_group);
3063                 put_device(dev_root);
3064                 if (ret)
3065                         return ret;
3066         }
3067
3068         for_each_possible_cpu(cpu) {
3069                 struct device *dev = get_cpu_device(cpu);
3070
3071                 if (!dev)
3072                         continue;
3073                 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
3074                 if (ret)
3075                         return ret;
3076         }
3077         return 0;
3078 }
3079 device_initcall(cpuhp_sysfs_init);
3080 #endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
3081
3082 /*
3083  * cpu_bit_bitmap[] is a special, "compressed" data structure that
3084  * represents all NR_CPUS bits binary values of 1<<nr.
3085  *
3086  * It is used by cpumask_of() to get a constant address to a CPU
3087  * mask value that has a single bit set only.
3088  */
3089
3090 /* cpu_bit_bitmap[0] is empty - so we can back into it */
3091 #define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
3092 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
3093 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
3094 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
3095
3096 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
3097
3098         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
3099         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
3100 #if BITS_PER_LONG > 32
3101         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
3102         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
3103 #endif
3104 };
3105 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
3106
3107 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
3108 EXPORT_SYMBOL(cpu_all_bits);
3109
3110 #ifdef CONFIG_INIT_ALL_POSSIBLE
3111 struct cpumask __cpu_possible_mask __read_mostly
3112         = {CPU_BITS_ALL};
3113 #else
3114 struct cpumask __cpu_possible_mask __read_mostly;
3115 #endif
3116 EXPORT_SYMBOL(__cpu_possible_mask);
3117
3118 struct cpumask __cpu_online_mask __read_mostly;
3119 EXPORT_SYMBOL(__cpu_online_mask);
3120
3121 struct cpumask __cpu_present_mask __read_mostly;
3122 EXPORT_SYMBOL(__cpu_present_mask);
3123
3124 struct cpumask __cpu_active_mask __read_mostly;
3125 EXPORT_SYMBOL(__cpu_active_mask);
3126
3127 struct cpumask __cpu_dying_mask __read_mostly;
3128 EXPORT_SYMBOL(__cpu_dying_mask);
3129
3130 atomic_t __num_online_cpus __read_mostly;
3131 EXPORT_SYMBOL(__num_online_cpus);
3132
3133 void init_cpu_present(const struct cpumask *src)
3134 {
3135         cpumask_copy(&__cpu_present_mask, src);
3136 }
3137
3138 void init_cpu_possible(const struct cpumask *src)
3139 {
3140         cpumask_copy(&__cpu_possible_mask, src);
3141 }
3142
3143 void init_cpu_online(const struct cpumask *src)
3144 {
3145         cpumask_copy(&__cpu_online_mask, src);
3146 }
3147
3148 void set_cpu_online(unsigned int cpu, bool online)
3149 {
3150         /*
3151          * atomic_inc/dec() is required to handle the horrid abuse of this
3152          * function by the reboot and kexec code which invoke it from
3153          * IPI/NMI broadcasts when shutting down CPUs. Invocation from
3154          * regular CPU hotplug is properly serialized.
3155          *
3156          * Note, that the fact that __num_online_cpus is of type atomic_t
3157          * does not protect readers which are not serialized against
3158          * concurrent hotplug operations.
3159          */
3160         if (online) {
3161                 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
3162                         atomic_inc(&__num_online_cpus);
3163         } else {
3164                 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
3165                         atomic_dec(&__num_online_cpus);
3166         }
3167 }
3168
3169 /*
3170  * Activate the first processor.
3171  */
3172 void __init boot_cpu_init(void)
3173 {
3174         int cpu = smp_processor_id();
3175
3176         /* Mark the boot cpu "present", "online" etc for SMP and UP case */
3177         set_cpu_online(cpu, true);
3178         set_cpu_active(cpu, true);
3179         set_cpu_present(cpu, true);
3180         set_cpu_possible(cpu, true);
3181
3182 #ifdef CONFIG_SMP
3183         __boot_cpu_id = cpu;
3184 #endif
3185 }
3186
3187 /*
3188  * Must be called _AFTER_ setting up the per_cpu areas
3189  */
3190 void __init boot_cpu_hotplug_init(void)
3191 {
3192 #ifdef CONFIG_SMP
3193         cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
3194         atomic_set(this_cpu_ptr(&cpuhp_state.ap_sync_state), SYNC_STATE_ONLINE);
3195 #endif
3196         this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
3197         this_cpu_write(cpuhp_state.target, CPUHP_ONLINE);
3198 }
3199
3200 /*
3201  * These are used for a global "mitigations=" cmdline option for toggling
3202  * optional CPU mitigations.
3203  */
3204 enum cpu_mitigations {
3205         CPU_MITIGATIONS_OFF,
3206         CPU_MITIGATIONS_AUTO,
3207         CPU_MITIGATIONS_AUTO_NOSMT,
3208 };
3209
3210 static enum cpu_mitigations cpu_mitigations __ro_after_init =
3211         CPU_MITIGATIONS_AUTO;
3212
3213 static int __init mitigations_parse_cmdline(char *arg)
3214 {
3215         if (!strcmp(arg, "off"))
3216                 cpu_mitigations = CPU_MITIGATIONS_OFF;
3217         else if (!strcmp(arg, "auto"))
3218                 cpu_mitigations = CPU_MITIGATIONS_AUTO;
3219         else if (!strcmp(arg, "auto,nosmt"))
3220                 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
3221         else
3222                 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
3223                         arg);
3224
3225         return 0;
3226 }
3227 early_param("mitigations", mitigations_parse_cmdline);
3228
3229 /* mitigations=off */
3230 bool cpu_mitigations_off(void)
3231 {
3232         return cpu_mitigations == CPU_MITIGATIONS_OFF;
3233 }
3234 EXPORT_SYMBOL_GPL(cpu_mitigations_off);
3235
3236 /* mitigations=auto,nosmt */
3237 bool cpu_mitigations_auto_nosmt(void)
3238 {
3239         return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
3240 }
3241 EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);