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Linux/kernel/time/clockevents.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * This file contains functions which manage clock event devices.
  4  *
  5  * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
  6  * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
  7  * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
  8  */
  9 
 10 #include <linux/clockchips.h>
 11 #include <linux/hrtimer.h>
 12 #include <linux/init.h>
 13 #include <linux/module.h>
 14 #include <linux/smp.h>
 15 #include <linux/device.h>
 16 
 17 #include "tick-internal.h"
 18 
 19 /* The registered clock event devices */
 20 static LIST_HEAD(clockevent_devices);
 21 static LIST_HEAD(clockevents_released);
 22 /* Protection for the above */
 23 static DEFINE_RAW_SPINLOCK(clockevents_lock);
 24 /* Protection for unbind operations */
 25 static DEFINE_MUTEX(clockevents_mutex);
 26 
 27 struct ce_unbind {
 28         struct clock_event_device *ce;
 29         int res;
 30 };
 31 
 32 static u64 cev_delta2ns(unsigned long latch, struct clock_event_device *evt,
 33                         bool ismax)
 34 {
 35         u64 clc = (u64) latch << evt->shift;
 36         u64 rnd;
 37 
 38         if (WARN_ON(!evt->mult))
 39                 evt->mult = 1;
 40         rnd = (u64) evt->mult - 1;
 41 
 42         /*
 43          * Upper bound sanity check. If the backwards conversion is
 44          * not equal latch, we know that the above shift overflowed.
 45          */
 46         if ((clc >> evt->shift) != (u64)latch)
 47                 clc = ~0ULL;
 48 
 49         /*
 50          * Scaled math oddities:
 51          *
 52          * For mult <= (1 << shift) we can safely add mult - 1 to
 53          * prevent integer rounding loss. So the backwards conversion
 54          * from nsec to device ticks will be correct.
 55          *
 56          * For mult > (1 << shift), i.e. device frequency is > 1GHz we
 57          * need to be careful. Adding mult - 1 will result in a value
 58          * which when converted back to device ticks can be larger
 59          * than latch by up to (mult - 1) >> shift. For the min_delta
 60          * calculation we still want to apply this in order to stay
 61          * above the minimum device ticks limit. For the upper limit
 62          * we would end up with a latch value larger than the upper
 63          * limit of the device, so we omit the add to stay below the
 64          * device upper boundary.
 65          *
 66          * Also omit the add if it would overflow the u64 boundary.
 67          */
 68         if ((~0ULL - clc > rnd) &&
 69             (!ismax || evt->mult <= (1ULL << evt->shift)))
 70                 clc += rnd;
 71 
 72         do_div(clc, evt->mult);
 73 
 74         /* Deltas less than 1usec are pointless noise */
 75         return clc > 1000 ? clc : 1000;
 76 }
 77 
 78 /**
 79  * clockevents_delta2ns - Convert a latch value (device ticks) to nanoseconds
 80  * @latch:      value to convert
 81  * @evt:        pointer to clock event device descriptor
 82  *
 83  * Math helper, returns latch value converted to nanoseconds (bound checked)
 84  */
 85 u64 clockevent_delta2ns(unsigned long latch, struct clock_event_device *evt)
 86 {
 87         return cev_delta2ns(latch, evt, false);
 88 }
 89 EXPORT_SYMBOL_GPL(clockevent_delta2ns);
 90 
 91 static int __clockevents_switch_state(struct clock_event_device *dev,
 92                                       enum clock_event_state state)
 93 {
 94         if (dev->features & CLOCK_EVT_FEAT_DUMMY)
 95                 return 0;
 96 
 97         /* Transition with new state-specific callbacks */
 98         switch (state) {
 99         case CLOCK_EVT_STATE_DETACHED:
100                 /* The clockevent device is getting replaced. Shut it down. */
101 
102         case CLOCK_EVT_STATE_SHUTDOWN:
103                 if (dev->set_state_shutdown)
104                         return dev->set_state_shutdown(dev);
105                 return 0;
106 
107         case CLOCK_EVT_STATE_PERIODIC:
108                 /* Core internal bug */
109                 if (!(dev->features & CLOCK_EVT_FEAT_PERIODIC))
110                         return -ENOSYS;
111                 if (dev->set_state_periodic)
112                         return dev->set_state_periodic(dev);
113                 return 0;
114 
115         case CLOCK_EVT_STATE_ONESHOT:
116                 /* Core internal bug */
117                 if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
118                         return -ENOSYS;
119                 if (dev->set_state_oneshot)
120                         return dev->set_state_oneshot(dev);
121                 return 0;
122 
123         case CLOCK_EVT_STATE_ONESHOT_STOPPED:
124                 /* Core internal bug */
125                 if (WARN_ONCE(!clockevent_state_oneshot(dev),
126                               "Current state: %d\n",
127                               clockevent_get_state(dev)))
128                         return -EINVAL;
129 
130                 if (dev->set_state_oneshot_stopped)
131                         return dev->set_state_oneshot_stopped(dev);
132                 else
133                         return -ENOSYS;
134 
135         default:
136                 return -ENOSYS;
137         }
138 }
139 
140 /**
141  * clockevents_switch_state - set the operating state of a clock event device
142  * @dev:        device to modify
143  * @state:      new state
144  *
145  * Must be called with interrupts disabled !
146  */
147 void clockevents_switch_state(struct clock_event_device *dev,
148                               enum clock_event_state state)
149 {
150         if (clockevent_get_state(dev) != state) {
151                 if (__clockevents_switch_state(dev, state))
152                         return;
153 
154                 clockevent_set_state(dev, state);
155 
156                 /*
157                  * A nsec2cyc multiplicator of 0 is invalid and we'd crash
158                  * on it, so fix it up and emit a warning:
159                  */
160                 if (clockevent_state_oneshot(dev)) {
161                         if (WARN_ON(!dev->mult))
162                                 dev->mult = 1;
163                 }
164         }
165 }
166 
167 /**
168  * clockevents_shutdown - shutdown the device and clear next_event
169  * @dev:        device to shutdown
170  */
171 void clockevents_shutdown(struct clock_event_device *dev)
172 {
173         clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
174         dev->next_event = KTIME_MAX;
175 }
176 
177 /**
178  * clockevents_tick_resume -    Resume the tick device before using it again
179  * @dev:                        device to resume
180  */
181 int clockevents_tick_resume(struct clock_event_device *dev)
182 {
183         int ret = 0;
184 
185         if (dev->tick_resume)
186                 ret = dev->tick_resume(dev);
187 
188         return ret;
189 }
190 
191 #ifdef CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST
192 
193 /* Limit min_delta to a jiffie */
194 #define MIN_DELTA_LIMIT         (NSEC_PER_SEC / HZ)
195 
196 /**
197  * clockevents_increase_min_delta - raise minimum delta of a clock event device
198  * @dev:       device to increase the minimum delta
199  *
200  * Returns 0 on success, -ETIME when the minimum delta reached the limit.
201  */
202 static int clockevents_increase_min_delta(struct clock_event_device *dev)
203 {
204         /* Nothing to do if we already reached the limit */
205         if (dev->min_delta_ns >= MIN_DELTA_LIMIT) {
206                 printk_deferred(KERN_WARNING
207                                 "CE: Reprogramming failure. Giving up\n");
208                 dev->next_event = KTIME_MAX;
209                 return -ETIME;
210         }
211 
212         if (dev->min_delta_ns < 5000)
213                 dev->min_delta_ns = 5000;
214         else
215                 dev->min_delta_ns += dev->min_delta_ns >> 1;
216 
217         if (dev->min_delta_ns > MIN_DELTA_LIMIT)
218                 dev->min_delta_ns = MIN_DELTA_LIMIT;
219 
220         printk_deferred(KERN_WARNING
221                         "CE: %s increased min_delta_ns to %llu nsec\n",
222                         dev->name ? dev->name : "?",
223                         (unsigned long long) dev->min_delta_ns);
224         return 0;
225 }
226 
227 /**
228  * clockevents_program_min_delta - Set clock event device to the minimum delay.
229  * @dev:        device to program
230  *
231  * Returns 0 on success, -ETIME when the retry loop failed.
232  */
233 static int clockevents_program_min_delta(struct clock_event_device *dev)
234 {
235         unsigned long long clc;
236         int64_t delta;
237         int i;
238 
239         for (i = 0;;) {
240                 delta = dev->min_delta_ns;
241                 dev->next_event = ktime_add_ns(ktime_get(), delta);
242 
243                 if (clockevent_state_shutdown(dev))
244                         return 0;
245 
246                 dev->retries++;
247                 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
248                 if (dev->set_next_event((unsigned long) clc, dev) == 0)
249                         return 0;
250 
251                 if (++i > 2) {
252                         /*
253                          * We tried 3 times to program the device with the
254                          * given min_delta_ns. Try to increase the minimum
255                          * delta, if that fails as well get out of here.
256                          */
257                         if (clockevents_increase_min_delta(dev))
258                                 return -ETIME;
259                         i = 0;
260                 }
261         }
262 }
263 
264 #else  /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
265 
266 /**
267  * clockevents_program_min_delta - Set clock event device to the minimum delay.
268  * @dev:        device to program
269  *
270  * Returns 0 on success, -ETIME when the retry loop failed.
271  */
272 static int clockevents_program_min_delta(struct clock_event_device *dev)
273 {
274         unsigned long long clc;
275         int64_t delta = 0;
276         int i;
277 
278         for (i = 0; i < 10; i++) {
279                 delta += dev->min_delta_ns;
280                 dev->next_event = ktime_add_ns(ktime_get(), delta);
281 
282                 if (clockevent_state_shutdown(dev))
283                         return 0;
284 
285                 dev->retries++;
286                 clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
287                 if (dev->set_next_event((unsigned long) clc, dev) == 0)
288                         return 0;
289         }
290         return -ETIME;
291 }
292 
293 #endif /* CONFIG_GENERIC_CLOCKEVENTS_MIN_ADJUST */
294 
295 /**
296  * clockevents_program_event - Reprogram the clock event device.
297  * @dev:        device to program
298  * @expires:    absolute expiry time (monotonic clock)
299  * @force:      program minimum delay if expires can not be set
300  *
301  * Returns 0 on success, -ETIME when the event is in the past.
302  */
303 int clockevents_program_event(struct clock_event_device *dev, ktime_t expires,
304                               bool force)
305 {
306         unsigned long long clc;
307         int64_t delta;
308         int rc;
309 
310         if (WARN_ON_ONCE(expires < 0))
311                 return -ETIME;
312 
313         dev->next_event = expires;
314 
315         if (clockevent_state_shutdown(dev))
316                 return 0;
317 
318         /* We must be in ONESHOT state here */
319         WARN_ONCE(!clockevent_state_oneshot(dev), "Current state: %d\n",
320                   clockevent_get_state(dev));
321 
322         /* Shortcut for clockevent devices that can deal with ktime. */
323         if (dev->features & CLOCK_EVT_FEAT_KTIME)
324                 return dev->set_next_ktime(expires, dev);
325 
326         delta = ktime_to_ns(ktime_sub(expires, ktime_get()));
327         if (delta <= 0)
328                 return force ? clockevents_program_min_delta(dev) : -ETIME;
329 
330         delta = min(delta, (int64_t) dev->max_delta_ns);
331         delta = max(delta, (int64_t) dev->min_delta_ns);
332 
333         clc = ((unsigned long long) delta * dev->mult) >> dev->shift;
334         rc = dev->set_next_event((unsigned long) clc, dev);
335 
336         return (rc && force) ? clockevents_program_min_delta(dev) : rc;
337 }
338 
339 /*
340  * Called after a notify add to make devices available which were
341  * released from the notifier call.
342  */
343 static void clockevents_notify_released(void)
344 {
345         struct clock_event_device *dev;
346 
347         while (!list_empty(&clockevents_released)) {
348                 dev = list_entry(clockevents_released.next,
349                                  struct clock_event_device, list);
350                 list_del(&dev->list);
351                 list_add(&dev->list, &clockevent_devices);
352                 tick_check_new_device(dev);
353         }
354 }
355 
356 /*
357  * Try to install a replacement clock event device
358  */
359 static int clockevents_replace(struct clock_event_device *ced)
360 {
361         struct clock_event_device *dev, *newdev = NULL;
362 
363         list_for_each_entry(dev, &clockevent_devices, list) {
364                 if (dev == ced || !clockevent_state_detached(dev))
365                         continue;
366 
367                 if (!tick_check_replacement(newdev, dev))
368                         continue;
369 
370                 if (!try_module_get(dev->owner))
371                         continue;
372 
373                 if (newdev)
374                         module_put(newdev->owner);
375                 newdev = dev;
376         }
377         if (newdev) {
378                 tick_install_replacement(newdev);
379                 list_del_init(&ced->list);
380         }
381         return newdev ? 0 : -EBUSY;
382 }
383 
384 /*
385  * Called with clockevents_mutex and clockevents_lock held
386  */
387 static int __clockevents_try_unbind(struct clock_event_device *ced, int cpu)
388 {
389         /* Fast track. Device is unused */
390         if (clockevent_state_detached(ced)) {
391                 list_del_init(&ced->list);
392                 return 0;
393         }
394 
395         return ced == per_cpu(tick_cpu_device, cpu).evtdev ? -EAGAIN : -EBUSY;
396 }
397 
398 /*
399  * SMP function call to unbind a device
400  */
401 static void __clockevents_unbind(void *arg)
402 {
403         struct ce_unbind *cu = arg;
404         int res;
405 
406         raw_spin_lock(&clockevents_lock);
407         res = __clockevents_try_unbind(cu->ce, smp_processor_id());
408         if (res == -EAGAIN)
409                 res = clockevents_replace(cu->ce);
410         cu->res = res;
411         raw_spin_unlock(&clockevents_lock);
412 }
413 
414 /*
415  * Issues smp function call to unbind a per cpu device. Called with
416  * clockevents_mutex held.
417  */
418 static int clockevents_unbind(struct clock_event_device *ced, int cpu)
419 {
420         struct ce_unbind cu = { .ce = ced, .res = -ENODEV };
421 
422         smp_call_function_single(cpu, __clockevents_unbind, &cu, 1);
423         return cu.res;
424 }
425 
426 /*
427  * Unbind a clockevents device.
428  */
429 int clockevents_unbind_device(struct clock_event_device *ced, int cpu)
430 {
431         int ret;
432 
433         mutex_lock(&clockevents_mutex);
434         ret = clockevents_unbind(ced, cpu);
435         mutex_unlock(&clockevents_mutex);
436         return ret;
437 }
438 EXPORT_SYMBOL_GPL(clockevents_unbind_device);
439 
440 /**
441  * clockevents_register_device - register a clock event device
442  * @dev:        device to register
443  */
444 void clockevents_register_device(struct clock_event_device *dev)
445 {
446         unsigned long flags;
447 
448         /* Initialize state to DETACHED */
449         clockevent_set_state(dev, CLOCK_EVT_STATE_DETACHED);
450 
451         if (!dev->cpumask) {
452                 WARN_ON(num_possible_cpus() > 1);
453                 dev->cpumask = cpumask_of(smp_processor_id());
454         }
455 
456         if (dev->cpumask == cpu_all_mask) {
457                 WARN(1, "%s cpumask == cpu_all_mask, using cpu_possible_mask instead\n",
458                      dev->name);
459                 dev->cpumask = cpu_possible_mask;
460         }
461 
462         raw_spin_lock_irqsave(&clockevents_lock, flags);
463 
464         list_add(&dev->list, &clockevent_devices);
465         tick_check_new_device(dev);
466         clockevents_notify_released();
467 
468         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
469 }
470 EXPORT_SYMBOL_GPL(clockevents_register_device);
471 
472 static void clockevents_config(struct clock_event_device *dev, u32 freq)
473 {
474         u64 sec;
475 
476         if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
477                 return;
478 
479         /*
480          * Calculate the maximum number of seconds we can sleep. Limit
481          * to 10 minutes for hardware which can program more than
482          * 32bit ticks so we still get reasonable conversion values.
483          */
484         sec = dev->max_delta_ticks;
485         do_div(sec, freq);
486         if (!sec)
487                 sec = 1;
488         else if (sec > 600 && dev->max_delta_ticks > UINT_MAX)
489                 sec = 600;
490 
491         clockevents_calc_mult_shift(dev, freq, sec);
492         dev->min_delta_ns = cev_delta2ns(dev->min_delta_ticks, dev, false);
493         dev->max_delta_ns = cev_delta2ns(dev->max_delta_ticks, dev, true);
494 }
495 
496 /**
497  * clockevents_config_and_register - Configure and register a clock event device
498  * @dev:        device to register
499  * @freq:       The clock frequency
500  * @min_delta:  The minimum clock ticks to program in oneshot mode
501  * @max_delta:  The maximum clock ticks to program in oneshot mode
502  *
503  * min/max_delta can be 0 for devices which do not support oneshot mode.
504  */
505 void clockevents_config_and_register(struct clock_event_device *dev,
506                                      u32 freq, unsigned long min_delta,
507                                      unsigned long max_delta)
508 {
509         dev->min_delta_ticks = min_delta;
510         dev->max_delta_ticks = max_delta;
511         clockevents_config(dev, freq);
512         clockevents_register_device(dev);
513 }
514 EXPORT_SYMBOL_GPL(clockevents_config_and_register);
515 
516 int __clockevents_update_freq(struct clock_event_device *dev, u32 freq)
517 {
518         clockevents_config(dev, freq);
519 
520         if (clockevent_state_oneshot(dev))
521                 return clockevents_program_event(dev, dev->next_event, false);
522 
523         if (clockevent_state_periodic(dev))
524                 return __clockevents_switch_state(dev, CLOCK_EVT_STATE_PERIODIC);
525 
526         return 0;
527 }
528 
529 /**
530  * clockevents_update_freq - Update frequency and reprogram a clock event device.
531  * @dev:        device to modify
532  * @freq:       new device frequency
533  *
534  * Reconfigure and reprogram a clock event device in oneshot
535  * mode. Must be called on the cpu for which the device delivers per
536  * cpu timer events. If called for the broadcast device the core takes
537  * care of serialization.
538  *
539  * Returns 0 on success, -ETIME when the event is in the past.
540  */
541 int clockevents_update_freq(struct clock_event_device *dev, u32 freq)
542 {
543         unsigned long flags;
544         int ret;
545 
546         local_irq_save(flags);
547         ret = tick_broadcast_update_freq(dev, freq);
548         if (ret == -ENODEV)
549                 ret = __clockevents_update_freq(dev, freq);
550         local_irq_restore(flags);
551         return ret;
552 }
553 
554 /*
555  * Noop handler when we shut down an event device
556  */
557 void clockevents_handle_noop(struct clock_event_device *dev)
558 {
559 }
560 
561 /**
562  * clockevents_exchange_device - release and request clock devices
563  * @old:        device to release (can be NULL)
564  * @new:        device to request (can be NULL)
565  *
566  * Called from various tick functions with clockevents_lock held and
567  * interrupts disabled.
568  */
569 void clockevents_exchange_device(struct clock_event_device *old,
570                                  struct clock_event_device *new)
571 {
572         /*
573          * Caller releases a clock event device. We queue it into the
574          * released list and do a notify add later.
575          */
576         if (old) {
577                 module_put(old->owner);
578                 clockevents_switch_state(old, CLOCK_EVT_STATE_DETACHED);
579                 list_del(&old->list);
580                 list_add(&old->list, &clockevents_released);
581         }
582 
583         if (new) {
584                 BUG_ON(!clockevent_state_detached(new));
585                 clockevents_shutdown(new);
586         }
587 }
588 
589 /**
590  * clockevents_suspend - suspend clock devices
591  */
592 void clockevents_suspend(void)
593 {
594         struct clock_event_device *dev;
595 
596         list_for_each_entry_reverse(dev, &clockevent_devices, list)
597                 if (dev->suspend && !clockevent_state_detached(dev))
598                         dev->suspend(dev);
599 }
600 
601 /**
602  * clockevents_resume - resume clock devices
603  */
604 void clockevents_resume(void)
605 {
606         struct clock_event_device *dev;
607 
608         list_for_each_entry(dev, &clockevent_devices, list)
609                 if (dev->resume && !clockevent_state_detached(dev))
610                         dev->resume(dev);
611 }
612 
613 #ifdef CONFIG_HOTPLUG_CPU
614 
615 # ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
616 /**
617  * tick_offline_cpu - Take CPU out of the broadcast mechanism
618  * @cpu:        The outgoing CPU
619  *
620  * Called on the outgoing CPU after it took itself offline.
621  */
622 void tick_offline_cpu(unsigned int cpu)
623 {
624         raw_spin_lock(&clockevents_lock);
625         tick_broadcast_offline(cpu);
626         raw_spin_unlock(&clockevents_lock);
627 }
628 # endif
629 
630 /**
631  * tick_cleanup_dead_cpu - Cleanup the tick and clockevents of a dead cpu
632  */
633 void tick_cleanup_dead_cpu(int cpu)
634 {
635         struct clock_event_device *dev, *tmp;
636         unsigned long flags;
637 
638         raw_spin_lock_irqsave(&clockevents_lock, flags);
639 
640         tick_shutdown(cpu);
641         /*
642          * Unregister the clock event devices which were
643          * released from the users in the notify chain.
644          */
645         list_for_each_entry_safe(dev, tmp, &clockevents_released, list)
646                 list_del(&dev->list);
647         /*
648          * Now check whether the CPU has left unused per cpu devices
649          */
650         list_for_each_entry_safe(dev, tmp, &clockevent_devices, list) {
651                 if (cpumask_test_cpu(cpu, dev->cpumask) &&
652                     cpumask_weight(dev->cpumask) == 1 &&
653                     !tick_is_broadcast_device(dev)) {
654                         BUG_ON(!clockevent_state_detached(dev));
655                         list_del(&dev->list);
656                 }
657         }
658         raw_spin_unlock_irqrestore(&clockevents_lock, flags);
659 }
660 #endif
661 
662 #ifdef CONFIG_SYSFS
663 static struct bus_type clockevents_subsys = {
664         .name           = "clockevents",
665         .dev_name       = "clockevent",
666 };
667 
668 static DEFINE_PER_CPU(struct device, tick_percpu_dev);
669 static struct tick_device *tick_get_tick_dev(struct device *dev);
670 
671 static ssize_t sysfs_show_current_tick_dev(struct device *dev,
672                                            struct device_attribute *attr,
673                                            char *buf)
674 {
675         struct tick_device *td;
676         ssize_t count = 0;
677 
678         raw_spin_lock_irq(&clockevents_lock);
679         td = tick_get_tick_dev(dev);
680         if (td && td->evtdev)
681                 count = snprintf(buf, PAGE_SIZE, "%s\n", td->evtdev->name);
682         raw_spin_unlock_irq(&clockevents_lock);
683         return count;
684 }
685 static DEVICE_ATTR(current_device, 0444, sysfs_show_current_tick_dev, NULL);
686 
687 /* We don't support the abomination of removable broadcast devices */
688 static ssize_t sysfs_unbind_tick_dev(struct device *dev,
689                                      struct device_attribute *attr,
690                                      const char *buf, size_t count)
691 {
692         char name[CS_NAME_LEN];
693         ssize_t ret = sysfs_get_uname(buf, name, count);
694         struct clock_event_device *ce;
695 
696         if (ret < 0)
697                 return ret;
698 
699         ret = -ENODEV;
700         mutex_lock(&clockevents_mutex);
701         raw_spin_lock_irq(&clockevents_lock);
702         list_for_each_entry(ce, &clockevent_devices, list) {
703                 if (!strcmp(ce->name, name)) {
704                         ret = __clockevents_try_unbind(ce, dev->id);
705                         break;
706                 }
707         }
708         raw_spin_unlock_irq(&clockevents_lock);
709         /*
710          * We hold clockevents_mutex, so ce can't go away
711          */
712         if (ret == -EAGAIN)
713                 ret = clockevents_unbind(ce, dev->id);
714         mutex_unlock(&clockevents_mutex);
715         return ret ? ret : count;
716 }
717 static DEVICE_ATTR(unbind_device, 0200, NULL, sysfs_unbind_tick_dev);
718 
719 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
720 static struct device tick_bc_dev = {
721         .init_name      = "broadcast",
722         .id             = 0,
723         .bus            = &clockevents_subsys,
724 };
725 
726 static struct tick_device *tick_get_tick_dev(struct device *dev)
727 {
728         return dev == &tick_bc_dev ? tick_get_broadcast_device() :
729                 &per_cpu(tick_cpu_device, dev->id);
730 }
731 
732 static __init int tick_broadcast_init_sysfs(void)
733 {
734         int err = device_register(&tick_bc_dev);
735 
736         if (!err)
737                 err = device_create_file(&tick_bc_dev, &dev_attr_current_device);
738         return err;
739 }
740 #else
741 static struct tick_device *tick_get_tick_dev(struct device *dev)
742 {
743         return &per_cpu(tick_cpu_device, dev->id);
744 }
745 static inline int tick_broadcast_init_sysfs(void) { return 0; }
746 #endif
747 
748 static int __init tick_init_sysfs(void)
749 {
750         int cpu;
751 
752         for_each_possible_cpu(cpu) {
753                 struct device *dev = &per_cpu(tick_percpu_dev, cpu);
754                 int err;
755 
756                 dev->id = cpu;
757                 dev->bus = &clockevents_subsys;
758                 err = device_register(dev);
759                 if (!err)
760                         err = device_create_file(dev, &dev_attr_current_device);
761                 if (!err)
762                         err = device_create_file(dev, &dev_attr_unbind_device);
763                 if (err)
764                         return err;
765         }
766         return tick_broadcast_init_sysfs();
767 }
768 
769 static int __init clockevents_init_sysfs(void)
770 {
771         int err = subsys_system_register(&clockevents_subsys, NULL);
772 
773         if (!err)
774                 err = tick_init_sysfs();
775         return err;
776 }
777 device_initcall(clockevents_init_sysfs);
778 #endif /* SYSFS */
779 

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