1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * This file contains functions which emulate a local clock-event
   4 * device via a broadcast event source.
   5 *
   6 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
   7 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
   8 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
   9 */
  10#include <linux/cpu.h>
  11#include <linux/err.h>
  12#include <linux/hrtimer.h>
  13#include <linux/interrupt.h>
  14#include <linux/percpu.h>
  15#include <linux/profile.h>
  16#include <linux/sched.h>
  17#include <linux/smp.h>
  18#include <linux/module.h>
  19
  20#include "tick-internal.h"
  21
  22/*
  23 * Broadcast support for broken x86 hardware, where the local apic
  24 * timer stops in C3 state.
  25 */
  26
  27static struct tick_device tick_broadcast_device;
  28static cpumask_var_t tick_broadcast_mask __cpumask_var_read_mostly;
  29static cpumask_var_t tick_broadcast_on __cpumask_var_read_mostly;
  30static cpumask_var_t tmpmask __cpumask_var_read_mostly;
  31static int tick_broadcast_forced;
  32
  33static __cacheline_aligned_in_smp DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
  34
  35#ifdef CONFIG_TICK_ONESHOT
  36static DEFINE_PER_CPU(struct clock_event_device *, tick_oneshot_wakeup_device);
  37
  38static void tick_broadcast_setup_oneshot(struct clock_event_device *bc);
  39static void tick_broadcast_clear_oneshot(int cpu);
  40static void tick_resume_broadcast_oneshot(struct clock_event_device *bc);
  41# ifdef CONFIG_HOTPLUG_CPU
  42static void tick_broadcast_oneshot_offline(unsigned int cpu);
  43# endif
  44#else
  45static inline void tick_broadcast_setup_oneshot(struct clock_event_device *bc) { BUG(); }
  46static inline void tick_broadcast_clear_oneshot(int cpu) { }
  47static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
  48# ifdef CONFIG_HOTPLUG_CPU
  49static inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }
  50# endif
  51#endif
  52
  53/*
  54 * Debugging: see timer_list.c
  55 */
  56struct tick_device *tick_get_broadcast_device(void)
  57{
  58	return &tick_broadcast_device;
  59}
  60
  61struct cpumask *tick_get_broadcast_mask(void)
  62{
  63	return tick_broadcast_mask;
  64}
  65
  66static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu);
  67
  68const struct clock_event_device *tick_get_wakeup_device(int cpu)
  69{
  70	return tick_get_oneshot_wakeup_device(cpu);
  71}
  72
  73/*
  74 * Start the device in periodic mode
  75 */
  76static void tick_broadcast_start_periodic(struct clock_event_device *bc)
  77{
  78	if (bc)
  79		tick_setup_periodic(bc, 1);
  80}
  81
  82/*
  83 * Check, if the device can be utilized as broadcast device:
  84 */
  85static bool tick_check_broadcast_device(struct clock_event_device *curdev,
  86					struct clock_event_device *newdev)
  87{
  88	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
  89	    (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
  90	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
  91		return false;
  92
  93	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
  94	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
  95		return false;
  96
  97	return !curdev || newdev->rating > curdev->rating;
  98}
  99
 100#ifdef CONFIG_TICK_ONESHOT
 101static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
 102{
 103	return per_cpu(tick_oneshot_wakeup_device, cpu);
 104}
 105
 106static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
 107{
 108	/*
 109	 * If we woke up early and the tick was reprogrammed in the
 110	 * meantime then this may be spurious but harmless.
 111	 */
 112	tick_receive_broadcast();
 113}
 114
 115static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
 116					   int cpu)
 117{
 118	struct clock_event_device *curdev = tick_get_oneshot_wakeup_device(cpu);
 119
 120	if (!newdev)
 121		goto set_device;
 122
 123	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
 124	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
 125		 return false;
 126
 127	if (!(newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
 128	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
 129		return false;
 130
 131	if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
 132		return false;
 133
 134	if (curdev && newdev->rating <= curdev->rating)
 135		return false;
 136
 137	if (!try_module_get(newdev->owner))
 138		return false;
 139
 140	newdev->event_handler = tick_oneshot_wakeup_handler;
 141set_device:
 142	clockevents_exchange_device(curdev, newdev);
 143	per_cpu(tick_oneshot_wakeup_device, cpu) = newdev;
 144	return true;
 145}
 146#else
 147static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
 148{
 149	return NULL;
 150}
 151
 152static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
 153					   int cpu)
 154{
 155	return false;
 156}
 157#endif
 158
 159/*
 160 * Conditionally install/replace broadcast device
 161 */
 162void tick_install_broadcast_device(struct clock_event_device *dev, int cpu)
 163{
 164	struct clock_event_device *cur = tick_broadcast_device.evtdev;
 165
 166	if (tick_set_oneshot_wakeup_device(dev, cpu))
 167		return;
 168
 169	if (!tick_check_broadcast_device(cur, dev))
 170		return;
 171
 172	if (!try_module_get(dev->owner))
 173		return;
 174
 175	clockevents_exchange_device(cur, dev);
 176	if (cur)
 177		cur->event_handler = clockevents_handle_noop;
 178	tick_broadcast_device.evtdev = dev;
 179	if (!cpumask_empty(tick_broadcast_mask))
 180		tick_broadcast_start_periodic(dev);
 181
 182	if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
 183		return;
 184
 185	/*
 186	 * If the system already runs in oneshot mode, switch the newly
 187	 * registered broadcast device to oneshot mode explicitly.
 188	 */
 189	if (tick_broadcast_oneshot_active()) {
 190		tick_broadcast_switch_to_oneshot();
 191		return;
 192	}
 193
 194	/*
 195	 * Inform all cpus about this. We might be in a situation
 196	 * where we did not switch to oneshot mode because the per cpu
 197	 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
 198	 * of a oneshot capable broadcast device. Without that
 199	 * notification the systems stays stuck in periodic mode
 200	 * forever.
 201	 */
 202	tick_clock_notify();
 203}
 204
 205/*
 206 * Check, if the device is the broadcast device
 207 */
 208int tick_is_broadcast_device(struct clock_event_device *dev)
 209{
 210	return (dev && tick_broadcast_device.evtdev == dev);
 211}
 212
 213int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
 214{
 215	int ret = -ENODEV;
 216
 217	if (tick_is_broadcast_device(dev)) {
 218		raw_spin_lock(&tick_broadcast_lock);
 219		ret = __clockevents_update_freq(dev, freq);
 220		raw_spin_unlock(&tick_broadcast_lock);
 221	}
 222	return ret;
 223}
 224
 225
 226static void err_broadcast(const struct cpumask *mask)
 227{
 228	pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
 229}
 230
 231static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
 232{
 233	if (!dev->broadcast)
 234		dev->broadcast = tick_broadcast;
 235	if (!dev->broadcast) {
 236		pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
 237			     dev->name);
 238		dev->broadcast = err_broadcast;
 239	}
 240}
 241
 242/*
 243 * Check, if the device is dysfunctional and a placeholder, which
 244 * needs to be handled by the broadcast device.
 245 */
 246int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
 247{
 248	struct clock_event_device *bc = tick_broadcast_device.evtdev;
 249	unsigned long flags;
 250	int ret = 0;
 251
 252	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 253
 254	/*
 255	 * Devices might be registered with both periodic and oneshot
 256	 * mode disabled. This signals, that the device needs to be
 257	 * operated from the broadcast device and is a placeholder for
 258	 * the cpu local device.
 259	 */
 260	if (!tick_device_is_functional(dev)) {
 261		dev->event_handler = tick_handle_periodic;
 262		tick_device_setup_broadcast_func(dev);
 263		cpumask_set_cpu(cpu, tick_broadcast_mask);
 264		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 265			tick_broadcast_start_periodic(bc);
 266		else
 267			tick_broadcast_setup_oneshot(bc);
 268		ret = 1;
 269	} else {
 270		/*
 271		 * Clear the broadcast bit for this cpu if the
 272		 * device is not power state affected.
 273		 */
 274		if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 275			cpumask_clear_cpu(cpu, tick_broadcast_mask);
 276		else
 277			tick_device_setup_broadcast_func(dev);
 278
 279		/*
 280		 * Clear the broadcast bit if the CPU is not in
 281		 * periodic broadcast on state.
 282		 */
 283		if (!cpumask_test_cpu(cpu, tick_broadcast_on))
 284			cpumask_clear_cpu(cpu, tick_broadcast_mask);
 285
 286		switch (tick_broadcast_device.mode) {
 287		case TICKDEV_MODE_ONESHOT:
 288			/*
 289			 * If the system is in oneshot mode we can
 290			 * unconditionally clear the oneshot mask bit,
 291			 * because the CPU is running and therefore
 292			 * not in an idle state which causes the power
 293			 * state affected device to stop. Let the
 294			 * caller initialize the device.
 295			 */
 296			tick_broadcast_clear_oneshot(cpu);
 297			ret = 0;
 298			break;
 299
 300		case TICKDEV_MODE_PERIODIC:
 301			/*
 302			 * If the system is in periodic mode, check
 303			 * whether the broadcast device can be
 304			 * switched off now.
 305			 */
 306			if (cpumask_empty(tick_broadcast_mask) && bc)
 307				clockevents_shutdown(bc);
 308			/*
 309			 * If we kept the cpu in the broadcast mask,
 310			 * tell the caller to leave the per cpu device
 311			 * in shutdown state. The periodic interrupt
 312			 * is delivered by the broadcast device, if
 313			 * the broadcast device exists and is not
 314			 * hrtimer based.
 315			 */
 316			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
 317				ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
 318			break;
 319		default:
 320			break;
 321		}
 322	}
 323	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 324	return ret;
 325}
 326
 327int tick_receive_broadcast(void)
 328{
 329	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 330	struct clock_event_device *evt = td->evtdev;
 331
 332	if (!evt)
 333		return -ENODEV;
 334
 335	if (!evt->event_handler)
 336		return -EINVAL;
 337
 338	evt->event_handler(evt);
 339	return 0;
 340}
 341
 342/*
 343 * Broadcast the event to the cpus, which are set in the mask (mangled).
 344 */
 345static bool tick_do_broadcast(struct cpumask *mask)
 346{
 347	int cpu = smp_processor_id();
 348	struct tick_device *td;
 349	bool local = false;
 350
 351	/*
 352	 * Check, if the current cpu is in the mask
 353	 */
 354	if (cpumask_test_cpu(cpu, mask)) {
 355		struct clock_event_device *bc = tick_broadcast_device.evtdev;
 356
 357		cpumask_clear_cpu(cpu, mask);
 358		/*
 359		 * We only run the local handler, if the broadcast
 360		 * device is not hrtimer based. Otherwise we run into
 361		 * a hrtimer recursion.
 362		 *
 363		 * local timer_interrupt()
 364		 *   local_handler()
 365		 *     expire_hrtimers()
 366		 *       bc_handler()
 367		 *         local_handler()
 368		 *	     expire_hrtimers()
 369		 */
 370		local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);
 371	}
 372
 373	if (!cpumask_empty(mask)) {
 374		/*
 375		 * It might be necessary to actually check whether the devices
 376		 * have different broadcast functions. For now, just use the
 377		 * one of the first device. This works as long as we have this
 378		 * misfeature only on x86 (lapic)
 379		 */
 380		td = &per_cpu(tick_cpu_device, cpumask_first(mask));
 381		td->evtdev->broadcast(mask);
 382	}
 383	return local;
 384}
 385
 386/*
 387 * Periodic broadcast:
 388 * - invoke the broadcast handlers
 389 */
 390static bool tick_do_periodic_broadcast(void)
 391{
 392	cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
 393	return tick_do_broadcast(tmpmask);
 394}
 395
 396/*
 397 * Event handler for periodic broadcast ticks
 398 */
 399static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 400{
 401	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 402	bool bc_local;
 403
 404	raw_spin_lock(&tick_broadcast_lock);
 405
 406	/* Handle spurious interrupts gracefully */
 407	if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) {
 408		raw_spin_unlock(&tick_broadcast_lock);
 409		return;
 410	}
 411
 412	bc_local = tick_do_periodic_broadcast();
 413
 414	if (clockevent_state_oneshot(dev)) {
 415		ktime_t next = ktime_add_ns(dev->next_event, TICK_NSEC);
 416
 417		clockevents_program_event(dev, next, true);
 418	}
 419	raw_spin_unlock(&tick_broadcast_lock);
 420
 421	/*
 422	 * We run the handler of the local cpu after dropping
 423	 * tick_broadcast_lock because the handler might deadlock when
 424	 * trying to switch to oneshot mode.
 425	 */
 426	if (bc_local)
 427		td->evtdev->event_handler(td->evtdev);
 428}
 429
 430/**
 431 * tick_broadcast_control - Enable/disable or force broadcast mode
 432 * @mode:	The selected broadcast mode
 433 *
 434 * Called when the system enters a state where affected tick devices
 435 * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
 436 */
 437void tick_broadcast_control(enum tick_broadcast_mode mode)
 438{
 439	struct clock_event_device *bc, *dev;
 440	struct tick_device *td;
 441	int cpu, bc_stopped;
 442	unsigned long flags;
 443
 444	/* Protects also the local clockevent device. */
 445	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 446	td = this_cpu_ptr(&tick_cpu_device);
 447	dev = td->evtdev;
 448
 449	/*
 450	 * Is the device not affected by the powerstate ?
 451	 */
 452	if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
 453		goto out;
 454
 455	if (!tick_device_is_functional(dev))
 456		goto out;
 457
 458	cpu = smp_processor_id();
 459	bc = tick_broadcast_device.evtdev;
 460	bc_stopped = cpumask_empty(tick_broadcast_mask);
 461
 462	switch (mode) {
 463	case TICK_BROADCAST_FORCE:
 464		tick_broadcast_forced = 1;
 465		fallthrough;
 466	case TICK_BROADCAST_ON:
 467		cpumask_set_cpu(cpu, tick_broadcast_on);
 468		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
 469			/*
 470			 * Only shutdown the cpu local device, if:
 471			 *
 472			 * - the broadcast device exists
 473			 * - the broadcast device is not a hrtimer based one
 474			 * - the broadcast device is in periodic mode to
 475			 *   avoid a hiccup during switch to oneshot mode
 476			 */
 477			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
 478			    tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 479				clockevents_shutdown(dev);
 480		}
 481		break;
 482
 483	case TICK_BROADCAST_OFF:
 484		if (tick_broadcast_forced)
 485			break;
 486		cpumask_clear_cpu(cpu, tick_broadcast_on);
 487		if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
 488			if (tick_broadcast_device.mode ==
 489			    TICKDEV_MODE_PERIODIC)
 490				tick_setup_periodic(dev, 0);
 491		}
 492		break;
 493	}
 494
 495	if (bc) {
 496		if (cpumask_empty(tick_broadcast_mask)) {
 497			if (!bc_stopped)
 498				clockevents_shutdown(bc);
 499		} else if (bc_stopped) {
 500			if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 501				tick_broadcast_start_periodic(bc);
 502			else
 503				tick_broadcast_setup_oneshot(bc);
 504		}
 505	}
 506out:
 507	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 508}
 509EXPORT_SYMBOL_GPL(tick_broadcast_control);
 510
 511/*
 512 * Set the periodic handler depending on broadcast on/off
 513 */
 514void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 515{
 516	if (!broadcast)
 517		dev->event_handler = tick_handle_periodic;
 518	else
 519		dev->event_handler = tick_handle_periodic_broadcast;
 520}
 521
 522#ifdef CONFIG_HOTPLUG_CPU
 523static void tick_shutdown_broadcast(void)
 524{
 525	struct clock_event_device *bc = tick_broadcast_device.evtdev;
 526
 527	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 528		if (bc && cpumask_empty(tick_broadcast_mask))
 529			clockevents_shutdown(bc);
 530	}
 531}
 532
 533/*
 534 * Remove a CPU from broadcasting
 535 */
 536void tick_broadcast_offline(unsigned int cpu)
 537{
 538	raw_spin_lock(&tick_broadcast_lock);
 539	cpumask_clear_cpu(cpu, tick_broadcast_mask);
 540	cpumask_clear_cpu(cpu, tick_broadcast_on);
 541	tick_broadcast_oneshot_offline(cpu);
 542	tick_shutdown_broadcast();
 543	raw_spin_unlock(&tick_broadcast_lock);
 544}
 545
 546#endif
 547
 548void tick_suspend_broadcast(void)
 549{
 550	struct clock_event_device *bc;
 551	unsigned long flags;
 552
 553	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 554
 555	bc = tick_broadcast_device.evtdev;
 556	if (bc)
 557		clockevents_shutdown(bc);
 558
 559	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 560}
 561
 562/*
 563 * This is called from tick_resume_local() on a resuming CPU. That's
 564 * called from the core resume function, tick_unfreeze() and the magic XEN
 565 * resume hackery.
 566 *
 567 * In none of these cases the broadcast device mode can change and the
 568 * bit of the resuming CPU in the broadcast mask is safe as well.
 569 */
 570bool tick_resume_check_broadcast(void)
 571{
 572	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
 573		return false;
 574	else
 575		return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
 576}
 577
 578void tick_resume_broadcast(void)
 579{
 580	struct clock_event_device *bc;
 581	unsigned long flags;
 582
 583	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 584
 585	bc = tick_broadcast_device.evtdev;
 586
 587	if (bc) {
 588		clockevents_tick_resume(bc);
 589
 590		switch (tick_broadcast_device.mode) {
 591		case TICKDEV_MODE_PERIODIC:
 592			if (!cpumask_empty(tick_broadcast_mask))
 593				tick_broadcast_start_periodic(bc);
 594			break;
 595		case TICKDEV_MODE_ONESHOT:
 596			if (!cpumask_empty(tick_broadcast_mask))
 597				tick_resume_broadcast_oneshot(bc);
 598			break;
 599		}
 600	}
 601	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 602}
 603
 604#ifdef CONFIG_TICK_ONESHOT
 605
 606static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly;
 607static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly;
 608static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly;
 609
 610/*
 611 * Exposed for debugging: see timer_list.c
 612 */
 613struct cpumask *tick_get_broadcast_oneshot_mask(void)
 614{
 615	return tick_broadcast_oneshot_mask;
 616}
 617
 618/*
 619 * Called before going idle with interrupts disabled. Checks whether a
 620 * broadcast event from the other core is about to happen. We detected
 621 * that in tick_broadcast_oneshot_control(). The callsite can use this
 622 * to avoid a deep idle transition as we are about to get the
 623 * broadcast IPI right away.
 624 */
 625int tick_check_broadcast_expired(void)
 626{
 627	return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
 628}
 629
 630/*
 631 * Set broadcast interrupt affinity
 632 */
 633static void tick_broadcast_set_affinity(struct clock_event_device *bc,
 634					const struct cpumask *cpumask)
 635{
 636	if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
 637		return;
 638
 639	if (cpumask_equal(bc->cpumask, cpumask))
 640		return;
 641
 642	bc->cpumask = cpumask;
 643	irq_set_affinity(bc->irq, bc->cpumask);
 644}
 645
 646static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
 647				     ktime_t expires)
 648{
 649	if (!clockevent_state_oneshot(bc))
 650		clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
 651
 652	clockevents_program_event(bc, expires, 1);
 653	tick_broadcast_set_affinity(bc, cpumask_of(cpu));
 654}
 655
 656static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 657{
 658	clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
 659}
 660
 661/*
 662 * Called from irq_enter() when idle was interrupted to reenable the
 663 * per cpu device.
 664 */
 665void tick_check_oneshot_broadcast_this_cpu(void)
 666{
 667	if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
 668		struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 669
 670		/*
 671		 * We might be in the middle of switching over from
 672		 * periodic to oneshot. If the CPU has not yet
 673		 * switched over, leave the device alone.
 674		 */
 675		if (td->mode == TICKDEV_MODE_ONESHOT) {
 676			clockevents_switch_state(td->evtdev,
 677					      CLOCK_EVT_STATE_ONESHOT);
 678		}
 679	}
 680}
 681
 682/*
 683 * Handle oneshot mode broadcasting
 684 */
 685static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 686{
 687	struct tick_device *td;
 688	ktime_t now, next_event;
 689	int cpu, next_cpu = 0;
 690	bool bc_local;
 691
 692	raw_spin_lock(&tick_broadcast_lock);
 693	dev->next_event = KTIME_MAX;
 694	next_event = KTIME_MAX;
 695	cpumask_clear(tmpmask);
 696	now = ktime_get();
 697	/* Find all expired events */
 698	for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
 699		/*
 700		 * Required for !SMP because for_each_cpu() reports
 701		 * unconditionally CPU0 as set on UP kernels.
 702		 */
 703		if (!IS_ENABLED(CONFIG_SMP) &&
 704		    cpumask_empty(tick_broadcast_oneshot_mask))
 705			break;
 706
 707		td = &per_cpu(tick_cpu_device, cpu);
 708		if (td->evtdev->next_event <= now) {
 709			cpumask_set_cpu(cpu, tmpmask);
 710			/*
 711			 * Mark the remote cpu in the pending mask, so
 712			 * it can avoid reprogramming the cpu local
 713			 * timer in tick_broadcast_oneshot_control().
 714			 */
 715			cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
 716		} else if (td->evtdev->next_event < next_event) {
 717			next_event = td->evtdev->next_event;
 718			next_cpu = cpu;
 719		}
 720	}
 721
 722	/*
 723	 * Remove the current cpu from the pending mask. The event is
 724	 * delivered immediately in tick_do_broadcast() !
 725	 */
 726	cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
 727
 728	/* Take care of enforced broadcast requests */
 729	cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
 730	cpumask_clear(tick_broadcast_force_mask);
 731
 732	/*
 733	 * Sanity check. Catch the case where we try to broadcast to
 734	 * offline cpus.
 735	 */
 736	if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
 737		cpumask_and(tmpmask, tmpmask, cpu_online_mask);
 738
 739	/*
 740	 * Wakeup the cpus which have an expired event.
 741	 */
 742	bc_local = tick_do_broadcast(tmpmask);
 743
 744	/*
 745	 * Two reasons for reprogram:
 746	 *
 747	 * - The global event did not expire any CPU local
 748	 * events. This happens in dyntick mode, as the maximum PIT
 749	 * delta is quite small.
 750	 *
 751	 * - There are pending events on sleeping CPUs which were not
 752	 * in the event mask
 753	 */
 754	if (next_event != KTIME_MAX)
 755		tick_broadcast_set_event(dev, next_cpu, next_event);
 756
 757	raw_spin_unlock(&tick_broadcast_lock);
 758
 759	if (bc_local) {
 760		td = this_cpu_ptr(&tick_cpu_device);
 761		td->evtdev->event_handler(td->evtdev);
 762	}
 763}
 764
 765static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
 766{
 767	if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
 768		return 0;
 769	if (bc->next_event == KTIME_MAX)
 770		return 0;
 771	return bc->bound_on == cpu ? -EBUSY : 0;
 772}
 773
 774static void broadcast_shutdown_local(struct clock_event_device *bc,
 775				     struct clock_event_device *dev)
 776{
 777	/*
 778	 * For hrtimer based broadcasting we cannot shutdown the cpu
 779	 * local device if our own event is the first one to expire or
 780	 * if we own the broadcast timer.
 781	 */
 782	if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
 783		if (broadcast_needs_cpu(bc, smp_processor_id()))
 784			return;
 785		if (dev->next_event < bc->next_event)
 786			return;
 787	}
 788	clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
 789}
 790
 791static int ___tick_broadcast_oneshot_control(enum tick_broadcast_state state,
 792					     struct tick_device *td,
 793					     int cpu)
 794{
 795	struct clock_event_device *bc, *dev = td->evtdev;
 796	int ret = 0;
 797	ktime_t now;
 798
 799	raw_spin_lock(&tick_broadcast_lock);
 800	bc = tick_broadcast_device.evtdev;
 801
 802	if (state == TICK_BROADCAST_ENTER) {
 803		/*
 804		 * If the current CPU owns the hrtimer broadcast
 805		 * mechanism, it cannot go deep idle and we do not add
 806		 * the CPU to the broadcast mask. We don't have to go
 807		 * through the EXIT path as the local timer is not
 808		 * shutdown.
 809		 */
 810		ret = broadcast_needs_cpu(bc, cpu);
 811		if (ret)
 812			goto out;
 813
 814		/*
 815		 * If the broadcast device is in periodic mode, we
 816		 * return.
 817		 */
 818		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 819			/* If it is a hrtimer based broadcast, return busy */
 820			if (bc->features & CLOCK_EVT_FEAT_HRTIMER)
 821				ret = -EBUSY;
 822			goto out;
 823		}
 824
 825		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
 826			WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
 827
 828			/* Conditionally shut down the local timer. */
 829			broadcast_shutdown_local(bc, dev);
 830
 831			/*
 832			 * We only reprogram the broadcast timer if we
 833			 * did not mark ourself in the force mask and
 834			 * if the cpu local event is earlier than the
 835			 * broadcast event. If the current CPU is in
 836			 * the force mask, then we are going to be
 837			 * woken by the IPI right away; we return
 838			 * busy, so the CPU does not try to go deep
 839			 * idle.
 840			 */
 841			if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
 842				ret = -EBUSY;
 843			} else if (dev->next_event < bc->next_event) {
 844				tick_broadcast_set_event(bc, cpu, dev->next_event);
 845				/*
 846				 * In case of hrtimer broadcasts the
 847				 * programming might have moved the
 848				 * timer to this cpu. If yes, remove
 849				 * us from the broadcast mask and
 850				 * return busy.
 851				 */
 852				ret = broadcast_needs_cpu(bc, cpu);
 853				if (ret) {
 854					cpumask_clear_cpu(cpu,
 855						tick_broadcast_oneshot_mask);
 856				}
 857			}
 858		}
 859	} else {
 860		if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
 861			clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
 862			/*
 863			 * The cpu which was handling the broadcast
 864			 * timer marked this cpu in the broadcast
 865			 * pending mask and fired the broadcast
 866			 * IPI. So we are going to handle the expired
 867			 * event anyway via the broadcast IPI
 868			 * handler. No need to reprogram the timer
 869			 * with an already expired event.
 870			 */
 871			if (cpumask_test_and_clear_cpu(cpu,
 872				       tick_broadcast_pending_mask))
 873				goto out;
 874
 875			/*
 876			 * Bail out if there is no next event.
 877			 */
 878			if (dev->next_event == KTIME_MAX)
 879				goto out;
 880			/*
 881			 * If the pending bit is not set, then we are
 882			 * either the CPU handling the broadcast
 883			 * interrupt or we got woken by something else.
 884			 *
 885			 * We are no longer in the broadcast mask, so
 886			 * if the cpu local expiry time is already
 887			 * reached, we would reprogram the cpu local
 888			 * timer with an already expired event.
 889			 *
 890			 * This can lead to a ping-pong when we return
 891			 * to idle and therefore rearm the broadcast
 892			 * timer before the cpu local timer was able
 893			 * to fire. This happens because the forced
 894			 * reprogramming makes sure that the event
 895			 * will happen in the future and depending on
 896			 * the min_delta setting this might be far
 897			 * enough out that the ping-pong starts.
 898			 *
 899			 * If the cpu local next_event has expired
 900			 * then we know that the broadcast timer
 901			 * next_event has expired as well and
 902			 * broadcast is about to be handled. So we
 903			 * avoid reprogramming and enforce that the
 904			 * broadcast handler, which did not run yet,
 905			 * will invoke the cpu local handler.
 906			 *
 907			 * We cannot call the handler directly from
 908			 * here, because we might be in a NOHZ phase
 909			 * and we did not go through the irq_enter()
 910			 * nohz fixups.
 911			 */
 912			now = ktime_get();
 913			if (dev->next_event <= now) {
 914				cpumask_set_cpu(cpu, tick_broadcast_force_mask);
 915				goto out;
 916			}
 917			/*
 918			 * We got woken by something else. Reprogram
 919			 * the cpu local timer device.
 920			 */
 921			tick_program_event(dev->next_event, 1);
 922		}
 923	}
 924out:
 925	raw_spin_unlock(&tick_broadcast_lock);
 926	return ret;
 927}
 928
 929static int tick_oneshot_wakeup_control(enum tick_broadcast_state state,
 930				       struct tick_device *td,
 931				       int cpu)
 932{
 933	struct clock_event_device *dev, *wd;
 934
 935	dev = td->evtdev;
 936	if (td->mode != TICKDEV_MODE_ONESHOT)
 937		return -EINVAL;
 938
 939	wd = tick_get_oneshot_wakeup_device(cpu);
 940	if (!wd)
 941		return -ENODEV;
 942
 943	switch (state) {
 944	case TICK_BROADCAST_ENTER:
 945		clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
 946		clockevents_switch_state(wd, CLOCK_EVT_STATE_ONESHOT);
 947		clockevents_program_event(wd, dev->next_event, 1);
 948		break;
 949	case TICK_BROADCAST_EXIT:
 950		/* We may have transitioned to oneshot mode while idle */
 951		if (clockevent_get_state(wd) != CLOCK_EVT_STATE_ONESHOT)
 952			return -ENODEV;
 953	}
 954
 955	return 0;
 956}
 957
 958int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
 959{
 960	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 961	int cpu = smp_processor_id();
 962
 963	if (!tick_oneshot_wakeup_control(state, td, cpu))
 964		return 0;
 965
 966	if (tick_broadcast_device.evtdev)
 967		return ___tick_broadcast_oneshot_control(state, td, cpu);
 968
 969	/*
 970	 * If there is no broadcast or wakeup device, tell the caller not
 971	 * to go into deep idle.
 972	 */
 973	return -EBUSY;
 974}
 975
 976/*
 977 * Reset the one shot broadcast for a cpu
 978 *
 979 * Called with tick_broadcast_lock held
 980 */
 981static void tick_broadcast_clear_oneshot(int cpu)
 982{
 983	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
 984	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
 985}
 986
 987static void tick_broadcast_init_next_event(struct cpumask *mask,
 988					   ktime_t expires)
 989{
 990	struct tick_device *td;
 991	int cpu;
 992
 993	for_each_cpu(cpu, mask) {
 994		td = &per_cpu(tick_cpu_device, cpu);
 995		if (td->evtdev)
 996			td->evtdev->next_event = expires;
 997	}
 998}
 999
1000static inline ktime_t tick_get_next_period(void)
1001{
1002	ktime_t next;
1003
1004	/*
1005	 * Protect against concurrent updates (store /load tearing on
1006	 * 32bit). It does not matter if the time is already in the
1007	 * past. The broadcast device which is about to be programmed will
1008	 * fire in any case.
1009	 */
1010	raw_spin_lock(&jiffies_lock);
1011	next = tick_next_period;
1012	raw_spin_unlock(&jiffies_lock);
1013	return next;
1014}
1015
1016/**
1017 * tick_broadcast_setup_oneshot - setup the broadcast device
1018 */
1019static void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
1020{
1021	int cpu = smp_processor_id();
1022
1023	if (!bc)
1024		return;
1025
1026	/* Set it up only once ! */
1027	if (bc->event_handler != tick_handle_oneshot_broadcast) {
1028		int was_periodic = clockevent_state_periodic(bc);
1029
1030		bc->event_handler = tick_handle_oneshot_broadcast;
1031
1032		/*
1033		 * We must be careful here. There might be other CPUs
1034		 * waiting for periodic broadcast. We need to set the
1035		 * oneshot_mask bits for those and program the
1036		 * broadcast device to fire.
1037		 */
1038		cpumask_copy(tmpmask, tick_broadcast_mask);
1039		cpumask_clear_cpu(cpu, tmpmask);
1040		cpumask_or(tick_broadcast_oneshot_mask,
1041			   tick_broadcast_oneshot_mask, tmpmask);
1042
1043		if (was_periodic && !cpumask_empty(tmpmask)) {
1044			ktime_t nextevt = tick_get_next_period();
1045
1046			clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
1047			tick_broadcast_init_next_event(tmpmask, nextevt);
1048			tick_broadcast_set_event(bc, cpu, nextevt);
1049		} else
1050			bc->next_event = KTIME_MAX;
1051	} else {
1052		/*
1053		 * The first cpu which switches to oneshot mode sets
1054		 * the bit for all other cpus which are in the general
1055		 * (periodic) broadcast mask. So the bit is set and
1056		 * would prevent the first broadcast enter after this
1057		 * to program the bc device.
1058		 */
1059		tick_broadcast_clear_oneshot(cpu);
1060	}
1061}
1062
1063/*
1064 * Select oneshot operating mode for the broadcast device
1065 */
1066void tick_broadcast_switch_to_oneshot(void)
1067{
1068	struct clock_event_device *bc;
1069	unsigned long flags;
1070
1071	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
1072
1073	tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
1074	bc = tick_broadcast_device.evtdev;
1075	if (bc)
1076		tick_broadcast_setup_oneshot(bc);
1077
1078	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
1079}
1080
1081#ifdef CONFIG_HOTPLUG_CPU
1082void hotplug_cpu__broadcast_tick_pull(int deadcpu)
1083{
1084	struct clock_event_device *bc;
1085	unsigned long flags;
1086
1087	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
1088	bc = tick_broadcast_device.evtdev;
1089
1090	if (bc && broadcast_needs_cpu(bc, deadcpu)) {
1091		/* This moves the broadcast assignment to this CPU: */
1092		clockevents_program_event(bc, bc->next_event, 1);
1093	}
1094	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
1095}
1096
1097/*
1098 * Remove a dying CPU from broadcasting
1099 */
1100static void tick_broadcast_oneshot_offline(unsigned int cpu)
1101{
1102	if (tick_get_oneshot_wakeup_device(cpu))
1103		tick_set_oneshot_wakeup_device(NULL, cpu);
1104
1105	/*
1106	 * Clear the broadcast masks for the dead cpu, but do not stop
1107	 * the broadcast device!
1108	 */
1109	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
1110	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
1111	cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
1112}
1113#endif
1114
1115/*
1116 * Check, whether the broadcast device is in one shot mode
1117 */
1118int tick_broadcast_oneshot_active(void)
1119{
1120	return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
1121}
1122
1123/*
1124 * Check whether the broadcast device supports oneshot.
1125 */
1126bool tick_broadcast_oneshot_available(void)
1127{
1128	struct clock_event_device *bc = tick_broadcast_device.evtdev;
1129
1130	return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
1131}
1132
1133#else
1134int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
1135{
1136	struct clock_event_device *bc = tick_broadcast_device.evtdev;
1137
1138	if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
1139		return -EBUSY;
1140
1141	return 0;
1142}
1143#endif
1144
1145void __init tick_broadcast_init(void)
1146{
1147	zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
1148	zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
1149	zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
1150#ifdef CONFIG_TICK_ONESHOT
1151	zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
1152	zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
1153	zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);
1154#endif
1155}