~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

TOMOYO Linux Cross Reference
Linux/kernel/cpu.c

Version: ~ [ linux-5.12-rc1 ] ~ [ linux-5.11.2 ] ~ [ linux-5.10.19 ] ~ [ linux-5.9.16 ] ~ [ linux-5.8.18 ] ~ [ linux-5.7.19 ] ~ [ linux-5.6.19 ] ~ [ linux-5.5.19 ] ~ [ linux-5.4.101 ] ~ [ linux-5.3.18 ] ~ [ linux-5.2.21 ] ~ [ linux-5.1.21 ] ~ [ linux-5.0.21 ] ~ [ linux-4.20.17 ] ~ [ linux-4.19.177 ] ~ [ linux-4.18.20 ] ~ [ linux-4.17.19 ] ~ [ linux-4.16.18 ] ~ [ linux-4.15.18 ] ~ [ linux-4.14.222 ] ~ [ linux-4.13.16 ] ~ [ linux-4.12.14 ] ~ [ linux-4.11.12 ] ~ [ linux-4.10.17 ] ~ [ linux-4.9.258 ] ~ [ linux-4.8.17 ] ~ [ linux-4.7.10 ] ~ [ linux-4.6.7 ] ~ [ linux-4.5.7 ] ~ [ linux-4.4.258 ] ~ [ linux-4.3.6 ] ~ [ linux-4.2.8 ] ~ [ linux-4.1.52 ] ~ [ linux-4.0.9 ] ~ [ linux-3.18.140 ] ~ [ linux-3.16.85 ] ~ [ linux-3.14.79 ] ~ [ linux-3.12.74 ] ~ [ linux-3.10.108 ] ~ [ linux-2.6.32.71 ] ~ [ linux-2.6.0 ] ~ [ linux-2.4.37.11 ] ~ [ unix-v6-master ] ~ [ ccs-tools-1.8.5 ] ~ [ policy-sample ] ~
Architecture: ~ [ i386 ] ~ [ alpha ] ~ [ m68k ] ~ [ mips ] ~ [ ppc ] ~ [ sparc ] ~ [ sparc64 ] ~

  1 /* CPU control.
  2  * (C) 2001, 2002, 2003, 2004 Rusty Russell
  3  *
  4  * This code is licenced under the GPL.
  5  */
  6 #include <linux/proc_fs.h>
  7 #include <linux/smp.h>
  8 #include <linux/init.h>
  9 #include <linux/notifier.h>
 10 #include <linux/sched/signal.h>
 11 #include <linux/sched/hotplug.h>
 12 #include <linux/sched/isolation.h>
 13 #include <linux/sched/task.h>
 14 #include <linux/sched/smt.h>
 15 #include <linux/unistd.h>
 16 #include <linux/cpu.h>
 17 #include <linux/oom.h>
 18 #include <linux/rcupdate.h>
 19 #include <linux/export.h>
 20 #include <linux/bug.h>
 21 #include <linux/kthread.h>
 22 #include <linux/stop_machine.h>
 23 #include <linux/mutex.h>
 24 #include <linux/gfp.h>
 25 #include <linux/suspend.h>
 26 #include <linux/lockdep.h>
 27 #include <linux/tick.h>
 28 #include <linux/irq.h>
 29 #include <linux/nmi.h>
 30 #include <linux/smpboot.h>
 31 #include <linux/relay.h>
 32 #include <linux/slab.h>
 33 #include <linux/percpu-rwsem.h>
 34 
 35 #include <trace/events/power.h>
 36 #define CREATE_TRACE_POINTS
 37 #include <trace/events/cpuhp.h>
 38 
 39 #include "smpboot.h"
 40 
 41 /**
 42  * cpuhp_cpu_state - Per cpu hotplug state storage
 43  * @state:      The current cpu state
 44  * @target:     The target state
 45  * @thread:     Pointer to the hotplug thread
 46  * @should_run: Thread should execute
 47  * @rollback:   Perform a rollback
 48  * @single:     Single callback invocation
 49  * @bringup:    Single callback bringup or teardown selector
 50  * @cb_state:   The state for a single callback (install/uninstall)
 51  * @result:     Result of the operation
 52  * @done_up:    Signal completion to the issuer of the task for cpu-up
 53  * @done_down:  Signal completion to the issuer of the task for cpu-down
 54  */
 55 struct cpuhp_cpu_state {
 56         enum cpuhp_state        state;
 57         enum cpuhp_state        target;
 58         enum cpuhp_state        fail;
 59 #ifdef CONFIG_SMP
 60         struct task_struct      *thread;
 61         bool                    should_run;
 62         bool                    rollback;
 63         bool                    single;
 64         bool                    bringup;
 65         struct hlist_node       *node;
 66         struct hlist_node       *last;
 67         enum cpuhp_state        cb_state;
 68         int                     result;
 69         struct completion       done_up;
 70         struct completion       done_down;
 71 #endif
 72 };
 73 
 74 static DEFINE_PER_CPU(struct cpuhp_cpu_state, cpuhp_state) = {
 75         .fail = CPUHP_INVALID,
 76 };
 77 
 78 #ifdef CONFIG_SMP
 79 cpumask_t cpus_booted_once_mask;
 80 #endif
 81 
 82 #if defined(CONFIG_LOCKDEP) && defined(CONFIG_SMP)
 83 static struct lockdep_map cpuhp_state_up_map =
 84         STATIC_LOCKDEP_MAP_INIT("cpuhp_state-up", &cpuhp_state_up_map);
 85 static struct lockdep_map cpuhp_state_down_map =
 86         STATIC_LOCKDEP_MAP_INIT("cpuhp_state-down", &cpuhp_state_down_map);
 87 
 88 
 89 static inline void cpuhp_lock_acquire(bool bringup)
 90 {
 91         lock_map_acquire(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
 92 }
 93 
 94 static inline void cpuhp_lock_release(bool bringup)
 95 {
 96         lock_map_release(bringup ? &cpuhp_state_up_map : &cpuhp_state_down_map);
 97 }
 98 #else
 99 
100 static inline void cpuhp_lock_acquire(bool bringup) { }
101 static inline void cpuhp_lock_release(bool bringup) { }
102 
103 #endif
104 
105 /**
106  * cpuhp_step - Hotplug state machine step
107  * @name:       Name of the step
108  * @startup:    Startup function of the step
109  * @teardown:   Teardown function of the step
110  * @cant_stop:  Bringup/teardown can't be stopped at this step
111  */
112 struct cpuhp_step {
113         const char              *name;
114         union {
115                 int             (*single)(unsigned int cpu);
116                 int             (*multi)(unsigned int cpu,
117                                          struct hlist_node *node);
118         } startup;
119         union {
120                 int             (*single)(unsigned int cpu);
121                 int             (*multi)(unsigned int cpu,
122                                          struct hlist_node *node);
123         } teardown;
124         struct hlist_head       list;
125         bool                    cant_stop;
126         bool                    multi_instance;
127 };
128 
129 static DEFINE_MUTEX(cpuhp_state_mutex);
130 static struct cpuhp_step cpuhp_hp_states[];
131 
132 static struct cpuhp_step *cpuhp_get_step(enum cpuhp_state state)
133 {
134         return cpuhp_hp_states + state;
135 }
136 
137 /**
138  * cpuhp_invoke_callback _ Invoke the callbacks for a given state
139  * @cpu:        The cpu for which the callback should be invoked
140  * @state:      The state to do callbacks for
141  * @bringup:    True if the bringup callback should be invoked
142  * @node:       For multi-instance, do a single entry callback for install/remove
143  * @lastp:      For multi-instance rollback, remember how far we got
144  *
145  * Called from cpu hotplug and from the state register machinery.
146  */
147 static int cpuhp_invoke_callback(unsigned int cpu, enum cpuhp_state state,
148                                  bool bringup, struct hlist_node *node,
149                                  struct hlist_node **lastp)
150 {
151         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
152         struct cpuhp_step *step = cpuhp_get_step(state);
153         int (*cbm)(unsigned int cpu, struct hlist_node *node);
154         int (*cb)(unsigned int cpu);
155         int ret, cnt;
156 
157         if (st->fail == state) {
158                 st->fail = CPUHP_INVALID;
159 
160                 if (!(bringup ? step->startup.single : step->teardown.single))
161                         return 0;
162 
163                 return -EAGAIN;
164         }
165 
166         if (!step->multi_instance) {
167                 WARN_ON_ONCE(lastp && *lastp);
168                 cb = bringup ? step->startup.single : step->teardown.single;
169                 if (!cb)
170                         return 0;
171                 trace_cpuhp_enter(cpu, st->target, state, cb);
172                 ret = cb(cpu);
173                 trace_cpuhp_exit(cpu, st->state, state, ret);
174                 return ret;
175         }
176         cbm = bringup ? step->startup.multi : step->teardown.multi;
177         if (!cbm)
178                 return 0;
179 
180         /* Single invocation for instance add/remove */
181         if (node) {
182                 WARN_ON_ONCE(lastp && *lastp);
183                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
184                 ret = cbm(cpu, node);
185                 trace_cpuhp_exit(cpu, st->state, state, ret);
186                 return ret;
187         }
188 
189         /* State transition. Invoke on all instances */
190         cnt = 0;
191         hlist_for_each(node, &step->list) {
192                 if (lastp && node == *lastp)
193                         break;
194 
195                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
196                 ret = cbm(cpu, node);
197                 trace_cpuhp_exit(cpu, st->state, state, ret);
198                 if (ret) {
199                         if (!lastp)
200                                 goto err;
201 
202                         *lastp = node;
203                         return ret;
204                 }
205                 cnt++;
206         }
207         if (lastp)
208                 *lastp = NULL;
209         return 0;
210 err:
211         /* Rollback the instances if one failed */
212         cbm = !bringup ? step->startup.multi : step->teardown.multi;
213         if (!cbm)
214                 return ret;
215 
216         hlist_for_each(node, &step->list) {
217                 if (!cnt--)
218                         break;
219 
220                 trace_cpuhp_multi_enter(cpu, st->target, state, cbm, node);
221                 ret = cbm(cpu, node);
222                 trace_cpuhp_exit(cpu, st->state, state, ret);
223                 /*
224                  * Rollback must not fail,
225                  */
226                 WARN_ON_ONCE(ret);
227         }
228         return ret;
229 }
230 
231 #ifdef CONFIG_SMP
232 static bool cpuhp_is_ap_state(enum cpuhp_state state)
233 {
234         /*
235          * The extra check for CPUHP_TEARDOWN_CPU is only for documentation
236          * purposes as that state is handled explicitly in cpu_down.
237          */
238         return state > CPUHP_BRINGUP_CPU && state != CPUHP_TEARDOWN_CPU;
239 }
240 
241 static inline void wait_for_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
242 {
243         struct completion *done = bringup ? &st->done_up : &st->done_down;
244         wait_for_completion(done);
245 }
246 
247 static inline void complete_ap_thread(struct cpuhp_cpu_state *st, bool bringup)
248 {
249         struct completion *done = bringup ? &st->done_up : &st->done_down;
250         complete(done);
251 }
252 
253 /*
254  * The former STARTING/DYING states, ran with IRQs disabled and must not fail.
255  */
256 static bool cpuhp_is_atomic_state(enum cpuhp_state state)
257 {
258         return CPUHP_AP_IDLE_DEAD <= state && state < CPUHP_AP_ONLINE;
259 }
260 
261 /* Serializes the updates to cpu_online_mask, cpu_present_mask */
262 static DEFINE_MUTEX(cpu_add_remove_lock);
263 bool cpuhp_tasks_frozen;
264 EXPORT_SYMBOL_GPL(cpuhp_tasks_frozen);
265 
266 /*
267  * The following two APIs (cpu_maps_update_begin/done) must be used when
268  * attempting to serialize the updates to cpu_online_mask & cpu_present_mask.
269  */
270 void cpu_maps_update_begin(void)
271 {
272         mutex_lock(&cpu_add_remove_lock);
273 }
274 
275 void cpu_maps_update_done(void)
276 {
277         mutex_unlock(&cpu_add_remove_lock);
278 }
279 
280 /*
281  * If set, cpu_up and cpu_down will return -EBUSY and do nothing.
282  * Should always be manipulated under cpu_add_remove_lock
283  */
284 static int cpu_hotplug_disabled;
285 
286 #ifdef CONFIG_HOTPLUG_CPU
287 
288 DEFINE_STATIC_PERCPU_RWSEM(cpu_hotplug_lock);
289 
290 void cpus_read_lock(void)
291 {
292         percpu_down_read(&cpu_hotplug_lock);
293 }
294 EXPORT_SYMBOL_GPL(cpus_read_lock);
295 
296 int cpus_read_trylock(void)
297 {
298         return percpu_down_read_trylock(&cpu_hotplug_lock);
299 }
300 EXPORT_SYMBOL_GPL(cpus_read_trylock);
301 
302 void cpus_read_unlock(void)
303 {
304         percpu_up_read(&cpu_hotplug_lock);
305 }
306 EXPORT_SYMBOL_GPL(cpus_read_unlock);
307 
308 void cpus_write_lock(void)
309 {
310         percpu_down_write(&cpu_hotplug_lock);
311 }
312 
313 void cpus_write_unlock(void)
314 {
315         percpu_up_write(&cpu_hotplug_lock);
316 }
317 
318 void lockdep_assert_cpus_held(void)
319 {
320         /*
321          * We can't have hotplug operations before userspace starts running,
322          * and some init codepaths will knowingly not take the hotplug lock.
323          * This is all valid, so mute lockdep until it makes sense to report
324          * unheld locks.
325          */
326         if (system_state < SYSTEM_RUNNING)
327                 return;
328 
329         percpu_rwsem_assert_held(&cpu_hotplug_lock);
330 }
331 
332 static void lockdep_acquire_cpus_lock(void)
333 {
334         rwsem_acquire(&cpu_hotplug_lock.rw_sem.dep_map, 0, 0, _THIS_IP_);
335 }
336 
337 static void lockdep_release_cpus_lock(void)
338 {
339         rwsem_release(&cpu_hotplug_lock.rw_sem.dep_map, _THIS_IP_);
340 }
341 
342 /*
343  * Wait for currently running CPU hotplug operations to complete (if any) and
344  * disable future CPU hotplug (from sysfs). The 'cpu_add_remove_lock' protects
345  * the 'cpu_hotplug_disabled' flag. The same lock is also acquired by the
346  * hotplug path before performing hotplug operations. So acquiring that lock
347  * guarantees mutual exclusion from any currently running hotplug operations.
348  */
349 void cpu_hotplug_disable(void)
350 {
351         cpu_maps_update_begin();
352         cpu_hotplug_disabled++;
353         cpu_maps_update_done();
354 }
355 EXPORT_SYMBOL_GPL(cpu_hotplug_disable);
356 
357 static void __cpu_hotplug_enable(void)
358 {
359         if (WARN_ONCE(!cpu_hotplug_disabled, "Unbalanced cpu hotplug enable\n"))
360                 return;
361         cpu_hotplug_disabled--;
362 }
363 
364 void cpu_hotplug_enable(void)
365 {
366         cpu_maps_update_begin();
367         __cpu_hotplug_enable();
368         cpu_maps_update_done();
369 }
370 EXPORT_SYMBOL_GPL(cpu_hotplug_enable);
371 
372 #else
373 
374 static void lockdep_acquire_cpus_lock(void)
375 {
376 }
377 
378 static void lockdep_release_cpus_lock(void)
379 {
380 }
381 
382 #endif  /* CONFIG_HOTPLUG_CPU */
383 
384 /*
385  * Architectures that need SMT-specific errata handling during SMT hotplug
386  * should override this.
387  */
388 void __weak arch_smt_update(void) { }
389 
390 #ifdef CONFIG_HOTPLUG_SMT
391 enum cpuhp_smt_control cpu_smt_control __read_mostly = CPU_SMT_ENABLED;
392 
393 void __init cpu_smt_disable(bool force)
394 {
395         if (!cpu_smt_possible())
396                 return;
397 
398         if (force) {
399                 pr_info("SMT: Force disabled\n");
400                 cpu_smt_control = CPU_SMT_FORCE_DISABLED;
401         } else {
402                 pr_info("SMT: disabled\n");
403                 cpu_smt_control = CPU_SMT_DISABLED;
404         }
405 }
406 
407 /*
408  * The decision whether SMT is supported can only be done after the full
409  * CPU identification. Called from architecture code.
410  */
411 void __init cpu_smt_check_topology(void)
412 {
413         if (!topology_smt_supported())
414                 cpu_smt_control = CPU_SMT_NOT_SUPPORTED;
415 }
416 
417 static int __init smt_cmdline_disable(char *str)
418 {
419         cpu_smt_disable(str && !strcmp(str, "force"));
420         return 0;
421 }
422 early_param("nosmt", smt_cmdline_disable);
423 
424 static inline bool cpu_smt_allowed(unsigned int cpu)
425 {
426         if (cpu_smt_control == CPU_SMT_ENABLED)
427                 return true;
428 
429         if (topology_is_primary_thread(cpu))
430                 return true;
431 
432         /*
433          * On x86 it's required to boot all logical CPUs at least once so
434          * that the init code can get a chance to set CR4.MCE on each
435          * CPU. Otherwise, a broadacasted MCE observing CR4.MCE=0b on any
436          * core will shutdown the machine.
437          */
438         return !cpumask_test_cpu(cpu, &cpus_booted_once_mask);
439 }
440 
441 /* Returns true if SMT is not supported of forcefully (irreversibly) disabled */
442 bool cpu_smt_possible(void)
443 {
444         return cpu_smt_control != CPU_SMT_FORCE_DISABLED &&
445                 cpu_smt_control != CPU_SMT_NOT_SUPPORTED;
446 }
447 EXPORT_SYMBOL_GPL(cpu_smt_possible);
448 #else
449 static inline bool cpu_smt_allowed(unsigned int cpu) { return true; }
450 #endif
451 
452 static inline enum cpuhp_state
453 cpuhp_set_state(struct cpuhp_cpu_state *st, enum cpuhp_state target)
454 {
455         enum cpuhp_state prev_state = st->state;
456 
457         st->rollback = false;
458         st->last = NULL;
459 
460         st->target = target;
461         st->single = false;
462         st->bringup = st->state < target;
463 
464         return prev_state;
465 }
466 
467 static inline void
468 cpuhp_reset_state(struct cpuhp_cpu_state *st, enum cpuhp_state prev_state)
469 {
470         st->rollback = true;
471 
472         /*
473          * If we have st->last we need to undo partial multi_instance of this
474          * state first. Otherwise start undo at the previous state.
475          */
476         if (!st->last) {
477                 if (st->bringup)
478                         st->state--;
479                 else
480                         st->state++;
481         }
482 
483         st->target = prev_state;
484         st->bringup = !st->bringup;
485 }
486 
487 /* Regular hotplug invocation of the AP hotplug thread */
488 static void __cpuhp_kick_ap(struct cpuhp_cpu_state *st)
489 {
490         if (!st->single && st->state == st->target)
491                 return;
492 
493         st->result = 0;
494         /*
495          * Make sure the above stores are visible before should_run becomes
496          * true. Paired with the mb() above in cpuhp_thread_fun()
497          */
498         smp_mb();
499         st->should_run = true;
500         wake_up_process(st->thread);
501         wait_for_ap_thread(st, st->bringup);
502 }
503 
504 static int cpuhp_kick_ap(struct cpuhp_cpu_state *st, enum cpuhp_state target)
505 {
506         enum cpuhp_state prev_state;
507         int ret;
508 
509         prev_state = cpuhp_set_state(st, target);
510         __cpuhp_kick_ap(st);
511         if ((ret = st->result)) {
512                 cpuhp_reset_state(st, prev_state);
513                 __cpuhp_kick_ap(st);
514         }
515 
516         return ret;
517 }
518 
519 static int bringup_wait_for_ap(unsigned int cpu)
520 {
521         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
522 
523         /* Wait for the CPU to reach CPUHP_AP_ONLINE_IDLE */
524         wait_for_ap_thread(st, true);
525         if (WARN_ON_ONCE((!cpu_online(cpu))))
526                 return -ECANCELED;
527 
528         /* Unpark the hotplug thread of the target cpu */
529         kthread_unpark(st->thread);
530 
531         /*
532          * SMT soft disabling on X86 requires to bring the CPU out of the
533          * BIOS 'wait for SIPI' state in order to set the CR4.MCE bit.  The
534          * CPU marked itself as booted_once in notify_cpu_starting() so the
535          * cpu_smt_allowed() check will now return false if this is not the
536          * primary sibling.
537          */
538         if (!cpu_smt_allowed(cpu))
539                 return -ECANCELED;
540 
541         if (st->target <= CPUHP_AP_ONLINE_IDLE)
542                 return 0;
543 
544         return cpuhp_kick_ap(st, st->target);
545 }
546 
547 static int bringup_cpu(unsigned int cpu)
548 {
549         struct task_struct *idle = idle_thread_get(cpu);
550         int ret;
551 
552         /*
553          * Some architectures have to walk the irq descriptors to
554          * setup the vector space for the cpu which comes online.
555          * Prevent irq alloc/free across the bringup.
556          */
557         irq_lock_sparse();
558 
559         /* Arch-specific enabling code. */
560         ret = __cpu_up(cpu, idle);
561         irq_unlock_sparse();
562         if (ret)
563                 return ret;
564         return bringup_wait_for_ap(cpu);
565 }
566 
567 /*
568  * Hotplug state machine related functions
569  */
570 
571 static void undo_cpu_up(unsigned int cpu, struct cpuhp_cpu_state *st)
572 {
573         for (st->state--; st->state > st->target; st->state--)
574                 cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
575 }
576 
577 static inline bool can_rollback_cpu(struct cpuhp_cpu_state *st)
578 {
579         if (IS_ENABLED(CONFIG_HOTPLUG_CPU))
580                 return true;
581         /*
582          * When CPU hotplug is disabled, then taking the CPU down is not
583          * possible because takedown_cpu() and the architecture and
584          * subsystem specific mechanisms are not available. So the CPU
585          * which would be completely unplugged again needs to stay around
586          * in the current state.
587          */
588         return st->state <= CPUHP_BRINGUP_CPU;
589 }
590 
591 static int cpuhp_up_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
592                               enum cpuhp_state target)
593 {
594         enum cpuhp_state prev_state = st->state;
595         int ret = 0;
596 
597         while (st->state < target) {
598                 st->state++;
599                 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
600                 if (ret) {
601                         if (can_rollback_cpu(st)) {
602                                 st->target = prev_state;
603                                 undo_cpu_up(cpu, st);
604                         }
605                         break;
606                 }
607         }
608         return ret;
609 }
610 
611 /*
612  * The cpu hotplug threads manage the bringup and teardown of the cpus
613  */
614 static void cpuhp_create(unsigned int cpu)
615 {
616         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
617 
618         init_completion(&st->done_up);
619         init_completion(&st->done_down);
620 }
621 
622 static int cpuhp_should_run(unsigned int cpu)
623 {
624         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
625 
626         return st->should_run;
627 }
628 
629 /*
630  * Execute teardown/startup callbacks on the plugged cpu. Also used to invoke
631  * callbacks when a state gets [un]installed at runtime.
632  *
633  * Each invocation of this function by the smpboot thread does a single AP
634  * state callback.
635  *
636  * It has 3 modes of operation:
637  *  - single: runs st->cb_state
638  *  - up:     runs ++st->state, while st->state < st->target
639  *  - down:   runs st->state--, while st->state > st->target
640  *
641  * When complete or on error, should_run is cleared and the completion is fired.
642  */
643 static void cpuhp_thread_fun(unsigned int cpu)
644 {
645         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
646         bool bringup = st->bringup;
647         enum cpuhp_state state;
648 
649         if (WARN_ON_ONCE(!st->should_run))
650                 return;
651 
652         /*
653          * ACQUIRE for the cpuhp_should_run() load of ->should_run. Ensures
654          * that if we see ->should_run we also see the rest of the state.
655          */
656         smp_mb();
657 
658         /*
659          * The BP holds the hotplug lock, but we're now running on the AP,
660          * ensure that anybody asserting the lock is held, will actually find
661          * it so.
662          */
663         lockdep_acquire_cpus_lock();
664         cpuhp_lock_acquire(bringup);
665 
666         if (st->single) {
667                 state = st->cb_state;
668                 st->should_run = false;
669         } else {
670                 if (bringup) {
671                         st->state++;
672                         state = st->state;
673                         st->should_run = (st->state < st->target);
674                         WARN_ON_ONCE(st->state > st->target);
675                 } else {
676                         state = st->state;
677                         st->state--;
678                         st->should_run = (st->state > st->target);
679                         WARN_ON_ONCE(st->state < st->target);
680                 }
681         }
682 
683         WARN_ON_ONCE(!cpuhp_is_ap_state(state));
684 
685         if (cpuhp_is_atomic_state(state)) {
686                 local_irq_disable();
687                 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
688                 local_irq_enable();
689 
690                 /*
691                  * STARTING/DYING must not fail!
692                  */
693                 WARN_ON_ONCE(st->result);
694         } else {
695                 st->result = cpuhp_invoke_callback(cpu, state, bringup, st->node, &st->last);
696         }
697 
698         if (st->result) {
699                 /*
700                  * If we fail on a rollback, we're up a creek without no
701                  * paddle, no way forward, no way back. We loose, thanks for
702                  * playing.
703                  */
704                 WARN_ON_ONCE(st->rollback);
705                 st->should_run = false;
706         }
707 
708         cpuhp_lock_release(bringup);
709         lockdep_release_cpus_lock();
710 
711         if (!st->should_run)
712                 complete_ap_thread(st, bringup);
713 }
714 
715 /* Invoke a single callback on a remote cpu */
716 static int
717 cpuhp_invoke_ap_callback(int cpu, enum cpuhp_state state, bool bringup,
718                          struct hlist_node *node)
719 {
720         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
721         int ret;
722 
723         if (!cpu_online(cpu))
724                 return 0;
725 
726         cpuhp_lock_acquire(false);
727         cpuhp_lock_release(false);
728 
729         cpuhp_lock_acquire(true);
730         cpuhp_lock_release(true);
731 
732         /*
733          * If we are up and running, use the hotplug thread. For early calls
734          * we invoke the thread function directly.
735          */
736         if (!st->thread)
737                 return cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
738 
739         st->rollback = false;
740         st->last = NULL;
741 
742         st->node = node;
743         st->bringup = bringup;
744         st->cb_state = state;
745         st->single = true;
746 
747         __cpuhp_kick_ap(st);
748 
749         /*
750          * If we failed and did a partial, do a rollback.
751          */
752         if ((ret = st->result) && st->last) {
753                 st->rollback = true;
754                 st->bringup = !bringup;
755 
756                 __cpuhp_kick_ap(st);
757         }
758 
759         /*
760          * Clean up the leftovers so the next hotplug operation wont use stale
761          * data.
762          */
763         st->node = st->last = NULL;
764         return ret;
765 }
766 
767 static int cpuhp_kick_ap_work(unsigned int cpu)
768 {
769         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
770         enum cpuhp_state prev_state = st->state;
771         int ret;
772 
773         cpuhp_lock_acquire(false);
774         cpuhp_lock_release(false);
775 
776         cpuhp_lock_acquire(true);
777         cpuhp_lock_release(true);
778 
779         trace_cpuhp_enter(cpu, st->target, prev_state, cpuhp_kick_ap_work);
780         ret = cpuhp_kick_ap(st, st->target);
781         trace_cpuhp_exit(cpu, st->state, prev_state, ret);
782 
783         return ret;
784 }
785 
786 static struct smp_hotplug_thread cpuhp_threads = {
787         .store                  = &cpuhp_state.thread,
788         .create                 = &cpuhp_create,
789         .thread_should_run      = cpuhp_should_run,
790         .thread_fn              = cpuhp_thread_fun,
791         .thread_comm            = "cpuhp/%u",
792         .selfparking            = true,
793 };
794 
795 void __init cpuhp_threads_init(void)
796 {
797         BUG_ON(smpboot_register_percpu_thread(&cpuhp_threads));
798         kthread_unpark(this_cpu_read(cpuhp_state.thread));
799 }
800 
801 #ifdef CONFIG_HOTPLUG_CPU
802 /**
803  * clear_tasks_mm_cpumask - Safely clear tasks' mm_cpumask for a CPU
804  * @cpu: a CPU id
805  *
806  * This function walks all processes, finds a valid mm struct for each one and
807  * then clears a corresponding bit in mm's cpumask.  While this all sounds
808  * trivial, there are various non-obvious corner cases, which this function
809  * tries to solve in a safe manner.
810  *
811  * Also note that the function uses a somewhat relaxed locking scheme, so it may
812  * be called only for an already offlined CPU.
813  */
814 void clear_tasks_mm_cpumask(int cpu)
815 {
816         struct task_struct *p;
817 
818         /*
819          * This function is called after the cpu is taken down and marked
820          * offline, so its not like new tasks will ever get this cpu set in
821          * their mm mask. -- Peter Zijlstra
822          * Thus, we may use rcu_read_lock() here, instead of grabbing
823          * full-fledged tasklist_lock.
824          */
825         WARN_ON(cpu_online(cpu));
826         rcu_read_lock();
827         for_each_process(p) {
828                 struct task_struct *t;
829 
830                 /*
831                  * Main thread might exit, but other threads may still have
832                  * a valid mm. Find one.
833                  */
834                 t = find_lock_task_mm(p);
835                 if (!t)
836                         continue;
837                 cpumask_clear_cpu(cpu, mm_cpumask(t->mm));
838                 task_unlock(t);
839         }
840         rcu_read_unlock();
841 }
842 
843 /* Take this CPU down. */
844 static int take_cpu_down(void *_param)
845 {
846         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
847         enum cpuhp_state target = max((int)st->target, CPUHP_AP_OFFLINE);
848         int err, cpu = smp_processor_id();
849         int ret;
850 
851         /* Ensure this CPU doesn't handle any more interrupts. */
852         err = __cpu_disable();
853         if (err < 0)
854                 return err;
855 
856         /*
857          * We get here while we are in CPUHP_TEARDOWN_CPU state and we must not
858          * do this step again.
859          */
860         WARN_ON(st->state != CPUHP_TEARDOWN_CPU);
861         st->state--;
862         /* Invoke the former CPU_DYING callbacks */
863         for (; st->state > target; st->state--) {
864                 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
865                 /*
866                  * DYING must not fail!
867                  */
868                 WARN_ON_ONCE(ret);
869         }
870 
871         /* Give up timekeeping duties */
872         tick_handover_do_timer();
873         /* Remove CPU from timer broadcasting */
874         tick_offline_cpu(cpu);
875         /* Park the stopper thread */
876         stop_machine_park(cpu);
877         return 0;
878 }
879 
880 static int takedown_cpu(unsigned int cpu)
881 {
882         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
883         int err;
884 
885         /* Park the smpboot threads */
886         kthread_park(per_cpu_ptr(&cpuhp_state, cpu)->thread);
887 
888         /*
889          * Prevent irq alloc/free while the dying cpu reorganizes the
890          * interrupt affinities.
891          */
892         irq_lock_sparse();
893 
894         /*
895          * So now all preempt/rcu users must observe !cpu_active().
896          */
897         err = stop_machine_cpuslocked(take_cpu_down, NULL, cpumask_of(cpu));
898         if (err) {
899                 /* CPU refused to die */
900                 irq_unlock_sparse();
901                 /* Unpark the hotplug thread so we can rollback there */
902                 kthread_unpark(per_cpu_ptr(&cpuhp_state, cpu)->thread);
903                 return err;
904         }
905         BUG_ON(cpu_online(cpu));
906 
907         /*
908          * The teardown callback for CPUHP_AP_SCHED_STARTING will have removed
909          * all runnable tasks from the CPU, there's only the idle task left now
910          * that the migration thread is done doing the stop_machine thing.
911          *
912          * Wait for the stop thread to go away.
913          */
914         wait_for_ap_thread(st, false);
915         BUG_ON(st->state != CPUHP_AP_IDLE_DEAD);
916 
917         /* Interrupts are moved away from the dying cpu, reenable alloc/free */
918         irq_unlock_sparse();
919 
920         hotplug_cpu__broadcast_tick_pull(cpu);
921         /* This actually kills the CPU. */
922         __cpu_die(cpu);
923 
924         tick_cleanup_dead_cpu(cpu);
925         rcutree_migrate_callbacks(cpu);
926         return 0;
927 }
928 
929 static void cpuhp_complete_idle_dead(void *arg)
930 {
931         struct cpuhp_cpu_state *st = arg;
932 
933         complete_ap_thread(st, false);
934 }
935 
936 void cpuhp_report_idle_dead(void)
937 {
938         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
939 
940         BUG_ON(st->state != CPUHP_AP_OFFLINE);
941         rcu_report_dead(smp_processor_id());
942         st->state = CPUHP_AP_IDLE_DEAD;
943         /*
944          * We cannot call complete after rcu_report_dead() so we delegate it
945          * to an online cpu.
946          */
947         smp_call_function_single(cpumask_first(cpu_online_mask),
948                                  cpuhp_complete_idle_dead, st, 0);
949 }
950 
951 static void undo_cpu_down(unsigned int cpu, struct cpuhp_cpu_state *st)
952 {
953         for (st->state++; st->state < st->target; st->state++)
954                 cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
955 }
956 
957 static int cpuhp_down_callbacks(unsigned int cpu, struct cpuhp_cpu_state *st,
958                                 enum cpuhp_state target)
959 {
960         enum cpuhp_state prev_state = st->state;
961         int ret = 0;
962 
963         for (; st->state > target; st->state--) {
964                 ret = cpuhp_invoke_callback(cpu, st->state, false, NULL, NULL);
965                 if (ret) {
966                         st->target = prev_state;
967                         if (st->state < prev_state)
968                                 undo_cpu_down(cpu, st);
969                         break;
970                 }
971         }
972         return ret;
973 }
974 
975 /* Requires cpu_add_remove_lock to be held */
976 static int __ref _cpu_down(unsigned int cpu, int tasks_frozen,
977                            enum cpuhp_state target)
978 {
979         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
980         int prev_state, ret = 0;
981 
982         if (num_online_cpus() == 1)
983                 return -EBUSY;
984 
985         if (!cpu_present(cpu))
986                 return -EINVAL;
987 
988         cpus_write_lock();
989 
990         cpuhp_tasks_frozen = tasks_frozen;
991 
992         prev_state = cpuhp_set_state(st, target);
993         /*
994          * If the current CPU state is in the range of the AP hotplug thread,
995          * then we need to kick the thread.
996          */
997         if (st->state > CPUHP_TEARDOWN_CPU) {
998                 st->target = max((int)target, CPUHP_TEARDOWN_CPU);
999                 ret = cpuhp_kick_ap_work(cpu);
1000                 /*
1001                  * The AP side has done the error rollback already. Just
1002                  * return the error code..
1003                  */
1004                 if (ret)
1005                         goto out;
1006 
1007                 /*
1008                  * We might have stopped still in the range of the AP hotplug
1009                  * thread. Nothing to do anymore.
1010                  */
1011                 if (st->state > CPUHP_TEARDOWN_CPU)
1012                         goto out;
1013 
1014                 st->target = target;
1015         }
1016         /*
1017          * The AP brought itself down to CPUHP_TEARDOWN_CPU. So we need
1018          * to do the further cleanups.
1019          */
1020         ret = cpuhp_down_callbacks(cpu, st, target);
1021         if (ret && st->state == CPUHP_TEARDOWN_CPU && st->state < prev_state) {
1022                 cpuhp_reset_state(st, prev_state);
1023                 __cpuhp_kick_ap(st);
1024         }
1025 
1026 out:
1027         cpus_write_unlock();
1028         /*
1029          * Do post unplug cleanup. This is still protected against
1030          * concurrent CPU hotplug via cpu_add_remove_lock.
1031          */
1032         lockup_detector_cleanup();
1033         arch_smt_update();
1034         return ret;
1035 }
1036 
1037 static int cpu_down_maps_locked(unsigned int cpu, enum cpuhp_state target)
1038 {
1039         if (cpu_hotplug_disabled)
1040                 return -EBUSY;
1041         return _cpu_down(cpu, 0, target);
1042 }
1043 
1044 static int do_cpu_down(unsigned int cpu, enum cpuhp_state target)
1045 {
1046         int err;
1047 
1048         cpu_maps_update_begin();
1049         err = cpu_down_maps_locked(cpu, target);
1050         cpu_maps_update_done();
1051         return err;
1052 }
1053 
1054 int cpu_down(unsigned int cpu)
1055 {
1056         return do_cpu_down(cpu, CPUHP_OFFLINE);
1057 }
1058 EXPORT_SYMBOL(cpu_down);
1059 
1060 #else
1061 #define takedown_cpu            NULL
1062 #endif /*CONFIG_HOTPLUG_CPU*/
1063 
1064 /**
1065  * notify_cpu_starting(cpu) - Invoke the callbacks on the starting CPU
1066  * @cpu: cpu that just started
1067  *
1068  * It must be called by the arch code on the new cpu, before the new cpu
1069  * enables interrupts and before the "boot" cpu returns from __cpu_up().
1070  */
1071 void notify_cpu_starting(unsigned int cpu)
1072 {
1073         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1074         enum cpuhp_state target = min((int)st->target, CPUHP_AP_ONLINE);
1075         int ret;
1076 
1077         rcu_cpu_starting(cpu);  /* Enables RCU usage on this CPU. */
1078         cpumask_set_cpu(cpu, &cpus_booted_once_mask);
1079         while (st->state < target) {
1080                 st->state++;
1081                 ret = cpuhp_invoke_callback(cpu, st->state, true, NULL, NULL);
1082                 /*
1083                  * STARTING must not fail!
1084                  */
1085                 WARN_ON_ONCE(ret);
1086         }
1087 }
1088 
1089 /*
1090  * Called from the idle task. Wake up the controlling task which brings the
1091  * hotplug thread of the upcoming CPU up and then delegates the rest of the
1092  * online bringup to the hotplug thread.
1093  */
1094 void cpuhp_online_idle(enum cpuhp_state state)
1095 {
1096         struct cpuhp_cpu_state *st = this_cpu_ptr(&cpuhp_state);
1097 
1098         /* Happens for the boot cpu */
1099         if (state != CPUHP_AP_ONLINE_IDLE)
1100                 return;
1101 
1102         /*
1103          * Unpart the stopper thread before we start the idle loop (and start
1104          * scheduling); this ensures the stopper task is always available.
1105          */
1106         stop_machine_unpark(smp_processor_id());
1107 
1108         st->state = CPUHP_AP_ONLINE_IDLE;
1109         complete_ap_thread(st, true);
1110 }
1111 
1112 /* Requires cpu_add_remove_lock to be held */
1113 static int _cpu_up(unsigned int cpu, int tasks_frozen, enum cpuhp_state target)
1114 {
1115         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1116         struct task_struct *idle;
1117         int ret = 0;
1118 
1119         cpus_write_lock();
1120 
1121         if (!cpu_present(cpu)) {
1122                 ret = -EINVAL;
1123                 goto out;
1124         }
1125 
1126         /*
1127          * The caller of do_cpu_up might have raced with another
1128          * caller. Ignore it for now.
1129          */
1130         if (st->state >= target)
1131                 goto out;
1132 
1133         if (st->state == CPUHP_OFFLINE) {
1134                 /* Let it fail before we try to bring the cpu up */
1135                 idle = idle_thread_get(cpu);
1136                 if (IS_ERR(idle)) {
1137                         ret = PTR_ERR(idle);
1138                         goto out;
1139                 }
1140         }
1141 
1142         cpuhp_tasks_frozen = tasks_frozen;
1143 
1144         cpuhp_set_state(st, target);
1145         /*
1146          * If the current CPU state is in the range of the AP hotplug thread,
1147          * then we need to kick the thread once more.
1148          */
1149         if (st->state > CPUHP_BRINGUP_CPU) {
1150                 ret = cpuhp_kick_ap_work(cpu);
1151                 /*
1152                  * The AP side has done the error rollback already. Just
1153                  * return the error code..
1154                  */
1155                 if (ret)
1156                         goto out;
1157         }
1158 
1159         /*
1160          * Try to reach the target state. We max out on the BP at
1161          * CPUHP_BRINGUP_CPU. After that the AP hotplug thread is
1162          * responsible for bringing it up to the target state.
1163          */
1164         target = min((int)target, CPUHP_BRINGUP_CPU);
1165         ret = cpuhp_up_callbacks(cpu, st, target);
1166 out:
1167         cpus_write_unlock();
1168         arch_smt_update();
1169         return ret;
1170 }
1171 
1172 static int do_cpu_up(unsigned int cpu, enum cpuhp_state target)
1173 {
1174         int err = 0;
1175 
1176         if (!cpu_possible(cpu)) {
1177                 pr_err("can't online cpu %d because it is not configured as may-hotadd at boot time\n",
1178                        cpu);
1179 #if defined(CONFIG_IA64)
1180                 pr_err("please check additional_cpus= boot parameter\n");
1181 #endif
1182                 return -EINVAL;
1183         }
1184 
1185         err = try_online_node(cpu_to_node(cpu));
1186         if (err)
1187                 return err;
1188 
1189         cpu_maps_update_begin();
1190 
1191         if (cpu_hotplug_disabled) {
1192                 err = -EBUSY;
1193                 goto out;
1194         }
1195         if (!cpu_smt_allowed(cpu)) {
1196                 err = -EPERM;
1197                 goto out;
1198         }
1199 
1200         err = _cpu_up(cpu, 0, target);
1201 out:
1202         cpu_maps_update_done();
1203         return err;
1204 }
1205 
1206 int cpu_up(unsigned int cpu)
1207 {
1208         return do_cpu_up(cpu, CPUHP_ONLINE);
1209 }
1210 EXPORT_SYMBOL_GPL(cpu_up);
1211 
1212 #ifdef CONFIG_PM_SLEEP_SMP
1213 static cpumask_var_t frozen_cpus;
1214 
1215 int __freeze_secondary_cpus(int primary, bool suspend)
1216 {
1217         int cpu, error = 0;
1218 
1219         cpu_maps_update_begin();
1220         if (primary == -1) {
1221                 primary = cpumask_first(cpu_online_mask);
1222                 if (!housekeeping_cpu(primary, HK_FLAG_TIMER))
1223                         primary = housekeeping_any_cpu(HK_FLAG_TIMER);
1224         } else {
1225                 if (!cpu_online(primary))
1226                         primary = cpumask_first(cpu_online_mask);
1227         }
1228 
1229         /*
1230          * We take down all of the non-boot CPUs in one shot to avoid races
1231          * with the userspace trying to use the CPU hotplug at the same time
1232          */
1233         cpumask_clear(frozen_cpus);
1234 
1235         pr_info("Disabling non-boot CPUs ...\n");
1236         for_each_online_cpu(cpu) {
1237                 if (cpu == primary)
1238                         continue;
1239 
1240                 if (suspend && pm_wakeup_pending()) {
1241                         pr_info("Wakeup pending. Abort CPU freeze\n");
1242                         error = -EBUSY;
1243                         break;
1244                 }
1245 
1246                 trace_suspend_resume(TPS("CPU_OFF"), cpu, true);
1247                 error = _cpu_down(cpu, 1, CPUHP_OFFLINE);
1248                 trace_suspend_resume(TPS("CPU_OFF"), cpu, false);
1249                 if (!error)
1250                         cpumask_set_cpu(cpu, frozen_cpus);
1251                 else {
1252                         pr_err("Error taking CPU%d down: %d\n", cpu, error);
1253                         break;
1254                 }
1255         }
1256 
1257         if (!error)
1258                 BUG_ON(num_online_cpus() > 1);
1259         else
1260                 pr_err("Non-boot CPUs are not disabled\n");
1261 
1262         /*
1263          * Make sure the CPUs won't be enabled by someone else. We need to do
1264          * this even in case of failure as all disable_nonboot_cpus() users are
1265          * supposed to do enable_nonboot_cpus() on the failure path.
1266          */
1267         cpu_hotplug_disabled++;
1268 
1269         cpu_maps_update_done();
1270         return error;
1271 }
1272 
1273 void __weak arch_enable_nonboot_cpus_begin(void)
1274 {
1275 }
1276 
1277 void __weak arch_enable_nonboot_cpus_end(void)
1278 {
1279 }
1280 
1281 void enable_nonboot_cpus(void)
1282 {
1283         int cpu, error;
1284 
1285         /* Allow everyone to use the CPU hotplug again */
1286         cpu_maps_update_begin();
1287         __cpu_hotplug_enable();
1288         if (cpumask_empty(frozen_cpus))
1289                 goto out;
1290 
1291         pr_info("Enabling non-boot CPUs ...\n");
1292 
1293         arch_enable_nonboot_cpus_begin();
1294 
1295         for_each_cpu(cpu, frozen_cpus) {
1296                 trace_suspend_resume(TPS("CPU_ON"), cpu, true);
1297                 error = _cpu_up(cpu, 1, CPUHP_ONLINE);
1298                 trace_suspend_resume(TPS("CPU_ON"), cpu, false);
1299                 if (!error) {
1300                         pr_info("CPU%d is up\n", cpu);
1301                         continue;
1302                 }
1303                 pr_warn("Error taking CPU%d up: %d\n", cpu, error);
1304         }
1305 
1306         arch_enable_nonboot_cpus_end();
1307 
1308         cpumask_clear(frozen_cpus);
1309 out:
1310         cpu_maps_update_done();
1311 }
1312 
1313 static int __init alloc_frozen_cpus(void)
1314 {
1315         if (!alloc_cpumask_var(&frozen_cpus, GFP_KERNEL|__GFP_ZERO))
1316                 return -ENOMEM;
1317         return 0;
1318 }
1319 core_initcall(alloc_frozen_cpus);
1320 
1321 /*
1322  * When callbacks for CPU hotplug notifications are being executed, we must
1323  * ensure that the state of the system with respect to the tasks being frozen
1324  * or not, as reported by the notification, remains unchanged *throughout the
1325  * duration* of the execution of the callbacks.
1326  * Hence we need to prevent the freezer from racing with regular CPU hotplug.
1327  *
1328  * This synchronization is implemented by mutually excluding regular CPU
1329  * hotplug and Suspend/Hibernate call paths by hooking onto the Suspend/
1330  * Hibernate notifications.
1331  */
1332 static int
1333 cpu_hotplug_pm_callback(struct notifier_block *nb,
1334                         unsigned long action, void *ptr)
1335 {
1336         switch (action) {
1337 
1338         case PM_SUSPEND_PREPARE:
1339         case PM_HIBERNATION_PREPARE:
1340                 cpu_hotplug_disable();
1341                 break;
1342 
1343         case PM_POST_SUSPEND:
1344         case PM_POST_HIBERNATION:
1345                 cpu_hotplug_enable();
1346                 break;
1347 
1348         default:
1349                 return NOTIFY_DONE;
1350         }
1351 
1352         return NOTIFY_OK;
1353 }
1354 
1355 
1356 static int __init cpu_hotplug_pm_sync_init(void)
1357 {
1358         /*
1359          * cpu_hotplug_pm_callback has higher priority than x86
1360          * bsp_pm_callback which depends on cpu_hotplug_pm_callback
1361          * to disable cpu hotplug to avoid cpu hotplug race.
1362          */
1363         pm_notifier(cpu_hotplug_pm_callback, 0);
1364         return 0;
1365 }
1366 core_initcall(cpu_hotplug_pm_sync_init);
1367 
1368 #endif /* CONFIG_PM_SLEEP_SMP */
1369 
1370 int __boot_cpu_id;
1371 
1372 #endif /* CONFIG_SMP */
1373 
1374 /* Boot processor state steps */
1375 static struct cpuhp_step cpuhp_hp_states[] = {
1376         [CPUHP_OFFLINE] = {
1377                 .name                   = "offline",
1378                 .startup.single         = NULL,
1379                 .teardown.single        = NULL,
1380         },
1381 #ifdef CONFIG_SMP
1382         [CPUHP_CREATE_THREADS]= {
1383                 .name                   = "threads:prepare",
1384                 .startup.single         = smpboot_create_threads,
1385                 .teardown.single        = NULL,
1386                 .cant_stop              = true,
1387         },
1388         [CPUHP_PERF_PREPARE] = {
1389                 .name                   = "perf:prepare",
1390                 .startup.single         = perf_event_init_cpu,
1391                 .teardown.single        = perf_event_exit_cpu,
1392         },
1393         [CPUHP_WORKQUEUE_PREP] = {
1394                 .name                   = "workqueue:prepare",
1395                 .startup.single         = workqueue_prepare_cpu,
1396                 .teardown.single        = NULL,
1397         },
1398         [CPUHP_HRTIMERS_PREPARE] = {
1399                 .name                   = "hrtimers:prepare",
1400                 .startup.single         = hrtimers_prepare_cpu,
1401                 .teardown.single        = hrtimers_dead_cpu,
1402         },
1403         [CPUHP_SMPCFD_PREPARE] = {
1404                 .name                   = "smpcfd:prepare",
1405                 .startup.single         = smpcfd_prepare_cpu,
1406                 .teardown.single        = smpcfd_dead_cpu,
1407         },
1408         [CPUHP_RELAY_PREPARE] = {
1409                 .name                   = "relay:prepare",
1410                 .startup.single         = relay_prepare_cpu,
1411                 .teardown.single        = NULL,
1412         },
1413         [CPUHP_SLAB_PREPARE] = {
1414                 .name                   = "slab:prepare",
1415                 .startup.single         = slab_prepare_cpu,
1416                 .teardown.single        = slab_dead_cpu,
1417         },
1418         [CPUHP_RCUTREE_PREP] = {
1419                 .name                   = "RCU/tree:prepare",
1420                 .startup.single         = rcutree_prepare_cpu,
1421                 .teardown.single        = rcutree_dead_cpu,
1422         },
1423         /*
1424          * On the tear-down path, timers_dead_cpu() must be invoked
1425          * before blk_mq_queue_reinit_notify() from notify_dead(),
1426          * otherwise a RCU stall occurs.
1427          */
1428         [CPUHP_TIMERS_PREPARE] = {
1429                 .name                   = "timers:prepare",
1430                 .startup.single         = timers_prepare_cpu,
1431                 .teardown.single        = timers_dead_cpu,
1432         },
1433         /* Kicks the plugged cpu into life */
1434         [CPUHP_BRINGUP_CPU] = {
1435                 .name                   = "cpu:bringup",
1436                 .startup.single         = bringup_cpu,
1437                 .teardown.single        = NULL,
1438                 .cant_stop              = true,
1439         },
1440         /* Final state before CPU kills itself */
1441         [CPUHP_AP_IDLE_DEAD] = {
1442                 .name                   = "idle:dead",
1443         },
1444         /*
1445          * Last state before CPU enters the idle loop to die. Transient state
1446          * for synchronization.
1447          */
1448         [CPUHP_AP_OFFLINE] = {
1449                 .name                   = "ap:offline",
1450                 .cant_stop              = true,
1451         },
1452         /* First state is scheduler control. Interrupts are disabled */
1453         [CPUHP_AP_SCHED_STARTING] = {
1454                 .name                   = "sched:starting",
1455                 .startup.single         = sched_cpu_starting,
1456                 .teardown.single        = sched_cpu_dying,
1457         },
1458         [CPUHP_AP_RCUTREE_DYING] = {
1459                 .name                   = "RCU/tree:dying",
1460                 .startup.single         = NULL,
1461                 .teardown.single        = rcutree_dying_cpu,
1462         },
1463         [CPUHP_AP_SMPCFD_DYING] = {
1464                 .name                   = "smpcfd:dying",
1465                 .startup.single         = NULL,
1466                 .teardown.single        = smpcfd_dying_cpu,
1467         },
1468         /* Entry state on starting. Interrupts enabled from here on. Transient
1469          * state for synchronsization */
1470         [CPUHP_AP_ONLINE] = {
1471                 .name                   = "ap:online",
1472         },
1473         /*
1474          * Handled on controll processor until the plugged processor manages
1475          * this itself.
1476          */
1477         [CPUHP_TEARDOWN_CPU] = {
1478                 .name                   = "cpu:teardown",
1479                 .startup.single         = NULL,
1480                 .teardown.single        = takedown_cpu,
1481                 .cant_stop              = true,
1482         },
1483         /* Handle smpboot threads park/unpark */
1484         [CPUHP_AP_SMPBOOT_THREADS] = {
1485                 .name                   = "smpboot/threads:online",
1486                 .startup.single         = smpboot_unpark_threads,
1487                 .teardown.single        = smpboot_park_threads,
1488         },
1489         [CPUHP_AP_IRQ_AFFINITY_ONLINE] = {
1490                 .name                   = "irq/affinity:online",
1491                 .startup.single         = irq_affinity_online_cpu,
1492                 .teardown.single        = NULL,
1493         },
1494         [CPUHP_AP_PERF_ONLINE] = {
1495                 .name                   = "perf:online",
1496                 .startup.single         = perf_event_init_cpu,
1497                 .teardown.single        = perf_event_exit_cpu,
1498         },
1499         [CPUHP_AP_WATCHDOG_ONLINE] = {
1500                 .name                   = "lockup_detector:online",
1501                 .startup.single         = lockup_detector_online_cpu,
1502                 .teardown.single        = lockup_detector_offline_cpu,
1503         },
1504         [CPUHP_AP_WORKQUEUE_ONLINE] = {
1505                 .name                   = "workqueue:online",
1506                 .startup.single         = workqueue_online_cpu,
1507                 .teardown.single        = workqueue_offline_cpu,
1508         },
1509         [CPUHP_AP_RCUTREE_ONLINE] = {
1510                 .name                   = "RCU/tree:online",
1511                 .startup.single         = rcutree_online_cpu,
1512                 .teardown.single        = rcutree_offline_cpu,
1513         },
1514 #endif
1515         /*
1516          * The dynamically registered state space is here
1517          */
1518 
1519 #ifdef CONFIG_SMP
1520         /* Last state is scheduler control setting the cpu active */
1521         [CPUHP_AP_ACTIVE] = {
1522                 .name                   = "sched:active",
1523                 .startup.single         = sched_cpu_activate,
1524                 .teardown.single        = sched_cpu_deactivate,
1525         },
1526 #endif
1527 
1528         /* CPU is fully up and running. */
1529         [CPUHP_ONLINE] = {
1530                 .name                   = "online",
1531                 .startup.single         = NULL,
1532                 .teardown.single        = NULL,
1533         },
1534 };
1535 
1536 /* Sanity check for callbacks */
1537 static int cpuhp_cb_check(enum cpuhp_state state)
1538 {
1539         if (state <= CPUHP_OFFLINE || state >= CPUHP_ONLINE)
1540                 return -EINVAL;
1541         return 0;
1542 }
1543 
1544 /*
1545  * Returns a free for dynamic slot assignment of the Online state. The states
1546  * are protected by the cpuhp_slot_states mutex and an empty slot is identified
1547  * by having no name assigned.
1548  */
1549 static int cpuhp_reserve_state(enum cpuhp_state state)
1550 {
1551         enum cpuhp_state i, end;
1552         struct cpuhp_step *step;
1553 
1554         switch (state) {
1555         case CPUHP_AP_ONLINE_DYN:
1556                 step = cpuhp_hp_states + CPUHP_AP_ONLINE_DYN;
1557                 end = CPUHP_AP_ONLINE_DYN_END;
1558                 break;
1559         case CPUHP_BP_PREPARE_DYN:
1560                 step = cpuhp_hp_states + CPUHP_BP_PREPARE_DYN;
1561                 end = CPUHP_BP_PREPARE_DYN_END;
1562                 break;
1563         default:
1564                 return -EINVAL;
1565         }
1566 
1567         for (i = state; i <= end; i++, step++) {
1568                 if (!step->name)
1569                         return i;
1570         }
1571         WARN(1, "No more dynamic states available for CPU hotplug\n");
1572         return -ENOSPC;
1573 }
1574 
1575 static int cpuhp_store_callbacks(enum cpuhp_state state, const char *name,
1576                                  int (*startup)(unsigned int cpu),
1577                                  int (*teardown)(unsigned int cpu),
1578                                  bool multi_instance)
1579 {
1580         /* (Un)Install the callbacks for further cpu hotplug operations */
1581         struct cpuhp_step *sp;
1582         int ret = 0;
1583 
1584         /*
1585          * If name is NULL, then the state gets removed.
1586          *
1587          * CPUHP_AP_ONLINE_DYN and CPUHP_BP_PREPARE_DYN are handed out on
1588          * the first allocation from these dynamic ranges, so the removal
1589          * would trigger a new allocation and clear the wrong (already
1590          * empty) state, leaving the callbacks of the to be cleared state
1591          * dangling, which causes wreckage on the next hotplug operation.
1592          */
1593         if (name && (state == CPUHP_AP_ONLINE_DYN ||
1594                      state == CPUHP_BP_PREPARE_DYN)) {
1595                 ret = cpuhp_reserve_state(state);
1596                 if (ret < 0)
1597                         return ret;
1598                 state = ret;
1599         }
1600         sp = cpuhp_get_step(state);
1601         if (name && sp->name)
1602                 return -EBUSY;
1603 
1604         sp->startup.single = startup;
1605         sp->teardown.single = teardown;
1606         sp->name = name;
1607         sp->multi_instance = multi_instance;
1608         INIT_HLIST_HEAD(&sp->list);
1609         return ret;
1610 }
1611 
1612 static void *cpuhp_get_teardown_cb(enum cpuhp_state state)
1613 {
1614         return cpuhp_get_step(state)->teardown.single;
1615 }
1616 
1617 /*
1618  * Call the startup/teardown function for a step either on the AP or
1619  * on the current CPU.
1620  */
1621 static int cpuhp_issue_call(int cpu, enum cpuhp_state state, bool bringup,
1622                             struct hlist_node *node)
1623 {
1624         struct cpuhp_step *sp = cpuhp_get_step(state);
1625         int ret;
1626 
1627         /*
1628          * If there's nothing to do, we done.
1629          * Relies on the union for multi_instance.
1630          */
1631         if ((bringup && !sp->startup.single) ||
1632             (!bringup && !sp->teardown.single))
1633                 return 0;
1634         /*
1635          * The non AP bound callbacks can fail on bringup. On teardown
1636          * e.g. module removal we crash for now.
1637          */
1638 #ifdef CONFIG_SMP
1639         if (cpuhp_is_ap_state(state))
1640                 ret = cpuhp_invoke_ap_callback(cpu, state, bringup, node);
1641         else
1642                 ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1643 #else
1644         ret = cpuhp_invoke_callback(cpu, state, bringup, node, NULL);
1645 #endif
1646         BUG_ON(ret && !bringup);
1647         return ret;
1648 }
1649 
1650 /*
1651  * Called from __cpuhp_setup_state on a recoverable failure.
1652  *
1653  * Note: The teardown callbacks for rollback are not allowed to fail!
1654  */
1655 static void cpuhp_rollback_install(int failedcpu, enum cpuhp_state state,
1656                                    struct hlist_node *node)
1657 {
1658         int cpu;
1659 
1660         /* Roll back the already executed steps on the other cpus */
1661         for_each_present_cpu(cpu) {
1662                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1663                 int cpustate = st->state;
1664 
1665                 if (cpu >= failedcpu)
1666                         break;
1667 
1668                 /* Did we invoke the startup call on that cpu ? */
1669                 if (cpustate >= state)
1670                         cpuhp_issue_call(cpu, state, false, node);
1671         }
1672 }
1673 
1674 int __cpuhp_state_add_instance_cpuslocked(enum cpuhp_state state,
1675                                           struct hlist_node *node,
1676                                           bool invoke)
1677 {
1678         struct cpuhp_step *sp;
1679         int cpu;
1680         int ret;
1681 
1682         lockdep_assert_cpus_held();
1683 
1684         sp = cpuhp_get_step(state);
1685         if (sp->multi_instance == false)
1686                 return -EINVAL;
1687 
1688         mutex_lock(&cpuhp_state_mutex);
1689 
1690         if (!invoke || !sp->startup.multi)
1691                 goto add_node;
1692 
1693         /*
1694          * Try to call the startup callback for each present cpu
1695          * depending on the hotplug state of the cpu.
1696          */
1697         for_each_present_cpu(cpu) {
1698                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1699                 int cpustate = st->state;
1700 
1701                 if (cpustate < state)
1702                         continue;
1703 
1704                 ret = cpuhp_issue_call(cpu, state, true, node);
1705                 if (ret) {
1706                         if (sp->teardown.multi)
1707                                 cpuhp_rollback_install(cpu, state, node);
1708                         goto unlock;
1709                 }
1710         }
1711 add_node:
1712         ret = 0;
1713         hlist_add_head(node, &sp->list);
1714 unlock:
1715         mutex_unlock(&cpuhp_state_mutex);
1716         return ret;
1717 }
1718 
1719 int __cpuhp_state_add_instance(enum cpuhp_state state, struct hlist_node *node,
1720                                bool invoke)
1721 {
1722         int ret;
1723 
1724         cpus_read_lock();
1725         ret = __cpuhp_state_add_instance_cpuslocked(state, node, invoke);
1726         cpus_read_unlock();
1727         return ret;
1728 }
1729 EXPORT_SYMBOL_GPL(__cpuhp_state_add_instance);
1730 
1731 /**
1732  * __cpuhp_setup_state_cpuslocked - Setup the callbacks for an hotplug machine state
1733  * @state:              The state to setup
1734  * @invoke:             If true, the startup function is invoked for cpus where
1735  *                      cpu state >= @state
1736  * @startup:            startup callback function
1737  * @teardown:           teardown callback function
1738  * @multi_instance:     State is set up for multiple instances which get
1739  *                      added afterwards.
1740  *
1741  * The caller needs to hold cpus read locked while calling this function.
1742  * Returns:
1743  *   On success:
1744  *      Positive state number if @state is CPUHP_AP_ONLINE_DYN
1745  *      0 for all other states
1746  *   On failure: proper (negative) error code
1747  */
1748 int __cpuhp_setup_state_cpuslocked(enum cpuhp_state state,
1749                                    const char *name, bool invoke,
1750                                    int (*startup)(unsigned int cpu),
1751                                    int (*teardown)(unsigned int cpu),
1752                                    bool multi_instance)
1753 {
1754         int cpu, ret = 0;
1755         bool dynstate;
1756 
1757         lockdep_assert_cpus_held();
1758 
1759         if (cpuhp_cb_check(state) || !name)
1760                 return -EINVAL;
1761 
1762         mutex_lock(&cpuhp_state_mutex);
1763 
1764         ret = cpuhp_store_callbacks(state, name, startup, teardown,
1765                                     multi_instance);
1766 
1767         dynstate = state == CPUHP_AP_ONLINE_DYN;
1768         if (ret > 0 && dynstate) {
1769                 state = ret;
1770                 ret = 0;
1771         }
1772 
1773         if (ret || !invoke || !startup)
1774                 goto out;
1775 
1776         /*
1777          * Try to call the startup callback for each present cpu
1778          * depending on the hotplug state of the cpu.
1779          */
1780         for_each_present_cpu(cpu) {
1781                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1782                 int cpustate = st->state;
1783 
1784                 if (cpustate < state)
1785                         continue;
1786 
1787                 ret = cpuhp_issue_call(cpu, state, true, NULL);
1788                 if (ret) {
1789                         if (teardown)
1790                                 cpuhp_rollback_install(cpu, state, NULL);
1791                         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1792                         goto out;
1793                 }
1794         }
1795 out:
1796         mutex_unlock(&cpuhp_state_mutex);
1797         /*
1798          * If the requested state is CPUHP_AP_ONLINE_DYN, return the
1799          * dynamically allocated state in case of success.
1800          */
1801         if (!ret && dynstate)
1802                 return state;
1803         return ret;
1804 }
1805 EXPORT_SYMBOL(__cpuhp_setup_state_cpuslocked);
1806 
1807 int __cpuhp_setup_state(enum cpuhp_state state,
1808                         const char *name, bool invoke,
1809                         int (*startup)(unsigned int cpu),
1810                         int (*teardown)(unsigned int cpu),
1811                         bool multi_instance)
1812 {
1813         int ret;
1814 
1815         cpus_read_lock();
1816         ret = __cpuhp_setup_state_cpuslocked(state, name, invoke, startup,
1817                                              teardown, multi_instance);
1818         cpus_read_unlock();
1819         return ret;
1820 }
1821 EXPORT_SYMBOL(__cpuhp_setup_state);
1822 
1823 int __cpuhp_state_remove_instance(enum cpuhp_state state,
1824                                   struct hlist_node *node, bool invoke)
1825 {
1826         struct cpuhp_step *sp = cpuhp_get_step(state);
1827         int cpu;
1828 
1829         BUG_ON(cpuhp_cb_check(state));
1830 
1831         if (!sp->multi_instance)
1832                 return -EINVAL;
1833 
1834         cpus_read_lock();
1835         mutex_lock(&cpuhp_state_mutex);
1836 
1837         if (!invoke || !cpuhp_get_teardown_cb(state))
1838                 goto remove;
1839         /*
1840          * Call the teardown callback for each present cpu depending
1841          * on the hotplug state of the cpu. This function is not
1842          * allowed to fail currently!
1843          */
1844         for_each_present_cpu(cpu) {
1845                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1846                 int cpustate = st->state;
1847 
1848                 if (cpustate >= state)
1849                         cpuhp_issue_call(cpu, state, false, node);
1850         }
1851 
1852 remove:
1853         hlist_del(node);
1854         mutex_unlock(&cpuhp_state_mutex);
1855         cpus_read_unlock();
1856 
1857         return 0;
1858 }
1859 EXPORT_SYMBOL_GPL(__cpuhp_state_remove_instance);
1860 
1861 /**
1862  * __cpuhp_remove_state_cpuslocked - Remove the callbacks for an hotplug machine state
1863  * @state:      The state to remove
1864  * @invoke:     If true, the teardown function is invoked for cpus where
1865  *              cpu state >= @state
1866  *
1867  * The caller needs to hold cpus read locked while calling this function.
1868  * The teardown callback is currently not allowed to fail. Think
1869  * about module removal!
1870  */
1871 void __cpuhp_remove_state_cpuslocked(enum cpuhp_state state, bool invoke)
1872 {
1873         struct cpuhp_step *sp = cpuhp_get_step(state);
1874         int cpu;
1875 
1876         BUG_ON(cpuhp_cb_check(state));
1877 
1878         lockdep_assert_cpus_held();
1879 
1880         mutex_lock(&cpuhp_state_mutex);
1881         if (sp->multi_instance) {
1882                 WARN(!hlist_empty(&sp->list),
1883                      "Error: Removing state %d which has instances left.\n",
1884                      state);
1885                 goto remove;
1886         }
1887 
1888         if (!invoke || !cpuhp_get_teardown_cb(state))
1889                 goto remove;
1890 
1891         /*
1892          * Call the teardown callback for each present cpu depending
1893          * on the hotplug state of the cpu. This function is not
1894          * allowed to fail currently!
1895          */
1896         for_each_present_cpu(cpu) {
1897                 struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, cpu);
1898                 int cpustate = st->state;
1899 
1900                 if (cpustate >= state)
1901                         cpuhp_issue_call(cpu, state, false, NULL);
1902         }
1903 remove:
1904         cpuhp_store_callbacks(state, NULL, NULL, NULL, false);
1905         mutex_unlock(&cpuhp_state_mutex);
1906 }
1907 EXPORT_SYMBOL(__cpuhp_remove_state_cpuslocked);
1908 
1909 void __cpuhp_remove_state(enum cpuhp_state state, bool invoke)
1910 {
1911         cpus_read_lock();
1912         __cpuhp_remove_state_cpuslocked(state, invoke);
1913         cpus_read_unlock();
1914 }
1915 EXPORT_SYMBOL(__cpuhp_remove_state);
1916 
1917 #ifdef CONFIG_HOTPLUG_SMT
1918 static void cpuhp_offline_cpu_device(unsigned int cpu)
1919 {
1920         struct device *dev = get_cpu_device(cpu);
1921 
1922         dev->offline = true;
1923         /* Tell user space about the state change */
1924         kobject_uevent(&dev->kobj, KOBJ_OFFLINE);
1925 }
1926 
1927 static void cpuhp_online_cpu_device(unsigned int cpu)
1928 {
1929         struct device *dev = get_cpu_device(cpu);
1930 
1931         dev->offline = false;
1932         /* Tell user space about the state change */
1933         kobject_uevent(&dev->kobj, KOBJ_ONLINE);
1934 }
1935 
1936 int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
1937 {
1938         int cpu, ret = 0;
1939 
1940         cpu_maps_update_begin();
1941         for_each_online_cpu(cpu) {
1942                 if (topology_is_primary_thread(cpu))
1943                         continue;
1944                 ret = cpu_down_maps_locked(cpu, CPUHP_OFFLINE);
1945                 if (ret)
1946                         break;
1947                 /*
1948                  * As this needs to hold the cpu maps lock it's impossible
1949                  * to call device_offline() because that ends up calling
1950                  * cpu_down() which takes cpu maps lock. cpu maps lock
1951                  * needs to be held as this might race against in kernel
1952                  * abusers of the hotplug machinery (thermal management).
1953                  *
1954                  * So nothing would update device:offline state. That would
1955                  * leave the sysfs entry stale and prevent onlining after
1956                  * smt control has been changed to 'off' again. This is
1957                  * called under the sysfs hotplug lock, so it is properly
1958                  * serialized against the regular offline usage.
1959                  */
1960                 cpuhp_offline_cpu_device(cpu);
1961         }
1962         if (!ret)
1963                 cpu_smt_control = ctrlval;
1964         cpu_maps_update_done();
1965         return ret;
1966 }
1967 
1968 int cpuhp_smt_enable(void)
1969 {
1970         int cpu, ret = 0;
1971 
1972         cpu_maps_update_begin();
1973         cpu_smt_control = CPU_SMT_ENABLED;
1974         for_each_present_cpu(cpu) {
1975                 /* Skip online CPUs and CPUs on offline nodes */
1976                 if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))
1977                         continue;
1978                 ret = _cpu_up(cpu, 0, CPUHP_ONLINE);
1979                 if (ret)
1980                         break;
1981                 /* See comment in cpuhp_smt_disable() */
1982                 cpuhp_online_cpu_device(cpu);
1983         }
1984         cpu_maps_update_done();
1985         return ret;
1986 }
1987 #endif
1988 
1989 #if defined(CONFIG_SYSFS) && defined(CONFIG_HOTPLUG_CPU)
1990 static ssize_t show_cpuhp_state(struct device *dev,
1991                                 struct device_attribute *attr, char *buf)
1992 {
1993         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
1994 
1995         return sprintf(buf, "%d\n", st->state);
1996 }
1997 static DEVICE_ATTR(state, 0444, show_cpuhp_state, NULL);
1998 
1999 static ssize_t write_cpuhp_target(struct device *dev,
2000                                   struct device_attribute *attr,
2001                                   const char *buf, size_t count)
2002 {
2003         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2004         struct cpuhp_step *sp;
2005         int target, ret;
2006 
2007         ret = kstrtoint(buf, 10, &target);
2008         if (ret)
2009                 return ret;
2010 
2011 #ifdef CONFIG_CPU_HOTPLUG_STATE_CONTROL
2012         if (target < CPUHP_OFFLINE || target > CPUHP_ONLINE)
2013                 return -EINVAL;
2014 #else
2015         if (target != CPUHP_OFFLINE && target != CPUHP_ONLINE)
2016                 return -EINVAL;
2017 #endif
2018 
2019         ret = lock_device_hotplug_sysfs();
2020         if (ret)
2021                 return ret;
2022 
2023         mutex_lock(&cpuhp_state_mutex);
2024         sp = cpuhp_get_step(target);
2025         ret = !sp->name || sp->cant_stop ? -EINVAL : 0;
2026         mutex_unlock(&cpuhp_state_mutex);
2027         if (ret)
2028                 goto out;
2029 
2030         if (st->state < target)
2031                 ret = do_cpu_up(dev->id, target);
2032         else
2033                 ret = do_cpu_down(dev->id, target);
2034 out:
2035         unlock_device_hotplug();
2036         return ret ? ret : count;
2037 }
2038 
2039 static ssize_t show_cpuhp_target(struct device *dev,
2040                                  struct device_attribute *attr, char *buf)
2041 {
2042         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2043 
2044         return sprintf(buf, "%d\n", st->target);
2045 }
2046 static DEVICE_ATTR(target, 0644, show_cpuhp_target, write_cpuhp_target);
2047 
2048 
2049 static ssize_t write_cpuhp_fail(struct device *dev,
2050                                 struct device_attribute *attr,
2051                                 const char *buf, size_t count)
2052 {
2053         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2054         struct cpuhp_step *sp;
2055         int fail, ret;
2056 
2057         ret = kstrtoint(buf, 10, &fail);
2058         if (ret)
2059                 return ret;
2060 
2061         if (fail < CPUHP_OFFLINE || fail > CPUHP_ONLINE)
2062                 return -EINVAL;
2063 
2064         /*
2065          * Cannot fail STARTING/DYING callbacks.
2066          */
2067         if (cpuhp_is_atomic_state(fail))
2068                 return -EINVAL;
2069 
2070         /*
2071          * Cannot fail anything that doesn't have callbacks.
2072          */
2073         mutex_lock(&cpuhp_state_mutex);
2074         sp = cpuhp_get_step(fail);
2075         if (!sp->startup.single && !sp->teardown.single)
2076                 ret = -EINVAL;
2077         mutex_unlock(&cpuhp_state_mutex);
2078         if (ret)
2079                 return ret;
2080 
2081         st->fail = fail;
2082 
2083         return count;
2084 }
2085 
2086 static ssize_t show_cpuhp_fail(struct device *dev,
2087                                struct device_attribute *attr, char *buf)
2088 {
2089         struct cpuhp_cpu_state *st = per_cpu_ptr(&cpuhp_state, dev->id);
2090 
2091         return sprintf(buf, "%d\n", st->fail);
2092 }
2093 
2094 static DEVICE_ATTR(fail, 0644, show_cpuhp_fail, write_cpuhp_fail);
2095 
2096 static struct attribute *cpuhp_cpu_attrs[] = {
2097         &dev_attr_state.attr,
2098         &dev_attr_target.attr,
2099         &dev_attr_fail.attr,
2100         NULL
2101 };
2102 
2103 static const struct attribute_group cpuhp_cpu_attr_group = {
2104         .attrs = cpuhp_cpu_attrs,
2105         .name = "hotplug",
2106         NULL
2107 };
2108 
2109 static ssize_t show_cpuhp_states(struct device *dev,
2110                                  struct device_attribute *attr, char *buf)
2111 {
2112         ssize_t cur, res = 0;
2113         int i;
2114 
2115         mutex_lock(&cpuhp_state_mutex);
2116         for (i = CPUHP_OFFLINE; i <= CPUHP_ONLINE; i++) {
2117                 struct cpuhp_step *sp = cpuhp_get_step(i);
2118 
2119                 if (sp->name) {
2120                         cur = sprintf(buf, "%3d: %s\n", i, sp->name);
2121                         buf += cur;
2122                         res += cur;
2123                 }
2124         }
2125         mutex_unlock(&cpuhp_state_mutex);
2126         return res;
2127 }
2128 static DEVICE_ATTR(states, 0444, show_cpuhp_states, NULL);
2129 
2130 static struct attribute *cpuhp_cpu_root_attrs[] = {
2131         &dev_attr_states.attr,
2132         NULL
2133 };
2134 
2135 static const struct attribute_group cpuhp_cpu_root_attr_group = {
2136         .attrs = cpuhp_cpu_root_attrs,
2137         .name = "hotplug",
2138         NULL
2139 };
2140 
2141 #ifdef CONFIG_HOTPLUG_SMT
2142 
2143 static ssize_t
2144 __store_smt_control(struct device *dev, struct device_attribute *attr,
2145                     const char *buf, size_t count)
2146 {
2147         int ctrlval, ret;
2148 
2149         if (sysfs_streq(buf, "on"))
2150                 ctrlval = CPU_SMT_ENABLED;
2151         else if (sysfs_streq(buf, "off"))
2152                 ctrlval = CPU_SMT_DISABLED;
2153         else if (sysfs_streq(buf, "forceoff"))
2154                 ctrlval = CPU_SMT_FORCE_DISABLED;
2155         else
2156                 return -EINVAL;
2157 
2158         if (cpu_smt_control == CPU_SMT_FORCE_DISABLED)
2159                 return -EPERM;
2160 
2161         if (cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
2162                 return -ENODEV;
2163 
2164         ret = lock_device_hotplug_sysfs();
2165         if (ret)
2166                 return ret;
2167 
2168         if (ctrlval != cpu_smt_control) {
2169                 switch (ctrlval) {
2170                 case CPU_SMT_ENABLED:
2171                         ret = cpuhp_smt_enable();
2172                         break;
2173                 case CPU_SMT_DISABLED:
2174                 case CPU_SMT_FORCE_DISABLED:
2175                         ret = cpuhp_smt_disable(ctrlval);
2176                         break;
2177                 }
2178         }
2179 
2180         unlock_device_hotplug();
2181         return ret ? ret : count;
2182 }
2183 
2184 #else /* !CONFIG_HOTPLUG_SMT */
2185 static ssize_t
2186 __store_smt_control(struct device *dev, struct device_attribute *attr,
2187                     const char *buf, size_t count)
2188 {
2189         return -ENODEV;
2190 }
2191 #endif /* CONFIG_HOTPLUG_SMT */
2192 
2193 static const char *smt_states[] = {
2194         [CPU_SMT_ENABLED]               = "on",
2195         [CPU_SMT_DISABLED]              = "off",
2196         [CPU_SMT_FORCE_DISABLED]        = "forceoff",
2197         [CPU_SMT_NOT_SUPPORTED]         = "notsupported",
2198         [CPU_SMT_NOT_IMPLEMENTED]       = "notimplemented",
2199 };
2200 
2201 static ssize_t
2202 show_smt_control(struct device *dev, struct device_attribute *attr, char *buf)
2203 {
2204         const char *state = smt_states[cpu_smt_control];
2205 
2206         return snprintf(buf, PAGE_SIZE - 2, "%s\n", state);
2207 }
2208 
2209 static ssize_t
2210 store_smt_control(struct device *dev, struct device_attribute *attr,
2211                   const char *buf, size_t count)
2212 {
2213         return __store_smt_control(dev, attr, buf, count);
2214 }
2215 static DEVICE_ATTR(control, 0644, show_smt_control, store_smt_control);
2216 
2217 static ssize_t
2218 show_smt_active(struct device *dev, struct device_attribute *attr, char *buf)
2219 {
2220         return snprintf(buf, PAGE_SIZE - 2, "%d\n", sched_smt_active());
2221 }
2222 static DEVICE_ATTR(active, 0444, show_smt_active, NULL);
2223 
2224 static struct attribute *cpuhp_smt_attrs[] = {
2225         &dev_attr_control.attr,
2226         &dev_attr_active.attr,
2227         NULL
2228 };
2229 
2230 static const struct attribute_group cpuhp_smt_attr_group = {
2231         .attrs = cpuhp_smt_attrs,
2232         .name = "smt",
2233         NULL
2234 };
2235 
2236 static int __init cpu_smt_sysfs_init(void)
2237 {
2238         return sysfs_create_group(&cpu_subsys.dev_root->kobj,
2239                                   &cpuhp_smt_attr_group);
2240 }
2241 
2242 static int __init cpuhp_sysfs_init(void)
2243 {
2244         int cpu, ret;
2245 
2246         ret = cpu_smt_sysfs_init();
2247         if (ret)
2248                 return ret;
2249 
2250         ret = sysfs_create_group(&cpu_subsys.dev_root->kobj,
2251                                  &cpuhp_cpu_root_attr_group);
2252         if (ret)
2253                 return ret;
2254 
2255         for_each_possible_cpu(cpu) {
2256                 struct device *dev = get_cpu_device(cpu);
2257 
2258                 if (!dev)
2259                         continue;
2260                 ret = sysfs_create_group(&dev->kobj, &cpuhp_cpu_attr_group);
2261                 if (ret)
2262                         return ret;
2263         }
2264         return 0;
2265 }
2266 device_initcall(cpuhp_sysfs_init);
2267 #endif /* CONFIG_SYSFS && CONFIG_HOTPLUG_CPU */
2268 
2269 /*
2270  * cpu_bit_bitmap[] is a special, "compressed" data structure that
2271  * represents all NR_CPUS bits binary values of 1<<nr.
2272  *
2273  * It is used by cpumask_of() to get a constant address to a CPU
2274  * mask value that has a single bit set only.
2275  */
2276 
2277 /* cpu_bit_bitmap[0] is empty - so we can back into it */
2278 #define MASK_DECLARE_1(x)       [x+1][0] = (1UL << (x))
2279 #define MASK_DECLARE_2(x)       MASK_DECLARE_1(x), MASK_DECLARE_1(x+1)
2280 #define MASK_DECLARE_4(x)       MASK_DECLARE_2(x), MASK_DECLARE_2(x+2)
2281 #define MASK_DECLARE_8(x)       MASK_DECLARE_4(x), MASK_DECLARE_4(x+4)
2282 
2283 const unsigned long cpu_bit_bitmap[BITS_PER_LONG+1][BITS_TO_LONGS(NR_CPUS)] = {
2284 
2285         MASK_DECLARE_8(0),      MASK_DECLARE_8(8),
2286         MASK_DECLARE_8(16),     MASK_DECLARE_8(24),
2287 #if BITS_PER_LONG > 32
2288         MASK_DECLARE_8(32),     MASK_DECLARE_8(40),
2289         MASK_DECLARE_8(48),     MASK_DECLARE_8(56),
2290 #endif
2291 };
2292 EXPORT_SYMBOL_GPL(cpu_bit_bitmap);
2293 
2294 const DECLARE_BITMAP(cpu_all_bits, NR_CPUS) = CPU_BITS_ALL;
2295 EXPORT_SYMBOL(cpu_all_bits);
2296 
2297 #ifdef CONFIG_INIT_ALL_POSSIBLE
2298 struct cpumask __cpu_possible_mask __read_mostly
2299         = {CPU_BITS_ALL};
2300 #else
2301 struct cpumask __cpu_possible_mask __read_mostly;
2302 #endif
2303 EXPORT_SYMBOL(__cpu_possible_mask);
2304 
2305 struct cpumask __cpu_online_mask __read_mostly;
2306 EXPORT_SYMBOL(__cpu_online_mask);
2307 
2308 struct cpumask __cpu_present_mask __read_mostly;
2309 EXPORT_SYMBOL(__cpu_present_mask);
2310 
2311 struct cpumask __cpu_active_mask __read_mostly;
2312 EXPORT_SYMBOL(__cpu_active_mask);
2313 
2314 atomic_t __num_online_cpus __read_mostly;
2315 EXPORT_SYMBOL(__num_online_cpus);
2316 
2317 void init_cpu_present(const struct cpumask *src)
2318 {
2319         cpumask_copy(&__cpu_present_mask, src);
2320 }
2321 
2322 void init_cpu_possible(const struct cpumask *src)
2323 {
2324         cpumask_copy(&__cpu_possible_mask, src);
2325 }
2326 
2327 void init_cpu_online(const struct cpumask *src)
2328 {
2329         cpumask_copy(&__cpu_online_mask, src);
2330 }
2331 
2332 void set_cpu_online(unsigned int cpu, bool online)
2333 {
2334         /*
2335          * atomic_inc/dec() is required to handle the horrid abuse of this
2336          * function by the reboot and kexec code which invoke it from
2337          * IPI/NMI broadcasts when shutting down CPUs. Invocation from
2338          * regular CPU hotplug is properly serialized.
2339          *
2340          * Note, that the fact that __num_online_cpus is of type atomic_t
2341          * does not protect readers which are not serialized against
2342          * concurrent hotplug operations.
2343          */
2344         if (online) {
2345                 if (!cpumask_test_and_set_cpu(cpu, &__cpu_online_mask))
2346                         atomic_inc(&__num_online_cpus);
2347         } else {
2348                 if (cpumask_test_and_clear_cpu(cpu, &__cpu_online_mask))
2349                         atomic_dec(&__num_online_cpus);
2350         }
2351 }
2352 
2353 /*
2354  * Activate the first processor.
2355  */
2356 void __init boot_cpu_init(void)
2357 {
2358         int cpu = smp_processor_id();
2359 
2360         /* Mark the boot cpu "present", "online" etc for SMP and UP case */
2361         set_cpu_online(cpu, true);
2362         set_cpu_active(cpu, true);
2363         set_cpu_present(cpu, true);
2364         set_cpu_possible(cpu, true);
2365 
2366 #ifdef CONFIG_SMP
2367         __boot_cpu_id = cpu;
2368 #endif
2369 }
2370 
2371 /*
2372  * Must be called _AFTER_ setting up the per_cpu areas
2373  */
2374 void __init boot_cpu_hotplug_init(void)
2375 {
2376 #ifdef CONFIG_SMP
2377         cpumask_set_cpu(smp_processor_id(), &cpus_booted_once_mask);
2378 #endif
2379         this_cpu_write(cpuhp_state.state, CPUHP_ONLINE);
2380 }
2381 
2382 /*
2383  * These are used for a global "mitigations=" cmdline option for toggling
2384  * optional CPU mitigations.
2385  */
2386 enum cpu_mitigations {
2387         CPU_MITIGATIONS_OFF,
2388         CPU_MITIGATIONS_AUTO,
2389         CPU_MITIGATIONS_AUTO_NOSMT,
2390 };
2391 
2392 static enum cpu_mitigations cpu_mitigations __ro_after_init =
2393         CPU_MITIGATIONS_AUTO;
2394 
2395 static int __init mitigations_parse_cmdline(char *arg)
2396 {
2397         if (!strcmp(arg, "off"))
2398                 cpu_mitigations = CPU_MITIGATIONS_OFF;
2399         else if (!strcmp(arg, "auto"))
2400                 cpu_mitigations = CPU_MITIGATIONS_AUTO;
2401         else if (!strcmp(arg, "auto,nosmt"))
2402                 cpu_mitigations = CPU_MITIGATIONS_AUTO_NOSMT;
2403         else
2404                 pr_crit("Unsupported mitigations=%s, system may still be vulnerable\n",
2405                         arg);
2406 
2407         return 0;
2408 }
2409 early_param("mitigations", mitigations_parse_cmdline);
2410 
2411 /* mitigations=off */
2412 bool cpu_mitigations_off(void)
2413 {
2414         return cpu_mitigations == CPU_MITIGATIONS_OFF;
2415 }
2416 EXPORT_SYMBOL_GPL(cpu_mitigations_off);
2417 
2418 /* mitigations=auto,nosmt */
2419 bool cpu_mitigations_auto_nosmt(void)
2420 {
2421         return cpu_mitigations == CPU_MITIGATIONS_AUTO_NOSMT;
2422 }
2423 EXPORT_SYMBOL_GPL(cpu_mitigations_auto_nosmt);
2424 

~ [ source navigation ] ~ [ diff markup ] ~ [ identifier search ] ~

kernel.org | git.kernel.org | LWN.net | Project Home | Wiki (Japanese) | Wiki (English) | SVN repository | Mail admin

Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.

osdn.jp