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, bool from_periodic);
  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
  46tick_broadcast_setup_oneshot(struct clock_event_device *bc, bool from_periodic) { BUG(); }
  47static inline void tick_broadcast_clear_oneshot(int cpu) { }
  48static inline void tick_resume_broadcast_oneshot(struct clock_event_device *bc) { }
  49# ifdef CONFIG_HOTPLUG_CPU
  50static inline void tick_broadcast_oneshot_offline(unsigned int cpu) { }
  51# endif
  52#endif
  53
  54/*
  55 * Debugging: see timer_list.c
  56 */
  57struct tick_device *tick_get_broadcast_device(void)
  58{
  59	return &tick_broadcast_device;
  60}
  61
  62struct cpumask *tick_get_broadcast_mask(void)
  63{
  64	return tick_broadcast_mask;
  65}
  66
  67static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu);
  68
  69const struct clock_event_device *tick_get_wakeup_device(int cpu)
  70{
  71	return tick_get_oneshot_wakeup_device(cpu);
  72}
  73
  74/*
  75 * Start the device in periodic mode
  76 */
  77static void tick_broadcast_start_periodic(struct clock_event_device *bc)
  78{
  79	if (bc)
  80		tick_setup_periodic(bc, 1);
  81}
  82
  83/*
  84 * Check, if the device can be utilized as broadcast device:
  85 */
  86static bool tick_check_broadcast_device(struct clock_event_device *curdev,
  87					struct clock_event_device *newdev)
  88{
  89	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
  90	    (newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
  91	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
  92		return false;
  93
  94	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT &&
  95	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
  96		return false;
  97
  98	return !curdev || newdev->rating > curdev->rating;
  99}
 100
 101#ifdef CONFIG_TICK_ONESHOT
 102static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
 103{
 104	return per_cpu(tick_oneshot_wakeup_device, cpu);
 105}
 106
 107static void tick_oneshot_wakeup_handler(struct clock_event_device *wd)
 108{
 109	/*
 110	 * If we woke up early and the tick was reprogrammed in the
 111	 * meantime then this may be spurious but harmless.
 112	 */
 113	tick_receive_broadcast();
 114}
 115
 116static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
 117					   int cpu)
 118{
 119	struct clock_event_device *curdev = tick_get_oneshot_wakeup_device(cpu);
 120
 121	if (!newdev)
 122		goto set_device;
 123
 124	if ((newdev->features & CLOCK_EVT_FEAT_DUMMY) ||
 125	    (newdev->features & CLOCK_EVT_FEAT_C3STOP))
 126		 return false;
 127
 128	if (!(newdev->features & CLOCK_EVT_FEAT_PERCPU) ||
 129	    !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
 130		return false;
 131
 132	if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu)))
 133		return false;
 134
 135	if (curdev && newdev->rating <= curdev->rating)
 136		return false;
 137
 138	if (!try_module_get(newdev->owner))
 139		return false;
 140
 141	newdev->event_handler = tick_oneshot_wakeup_handler;
 142set_device:
 143	clockevents_exchange_device(curdev, newdev);
 144	per_cpu(tick_oneshot_wakeup_device, cpu) = newdev;
 145	return true;
 146}
 147#else
 148static struct clock_event_device *tick_get_oneshot_wakeup_device(int cpu)
 149{
 150	return NULL;
 151}
 152
 153static bool tick_set_oneshot_wakeup_device(struct clock_event_device *newdev,
 154					   int cpu)
 155{
 156	return false;
 157}
 158#endif
 159
 160/*
 161 * Conditionally install/replace broadcast device
 162 */
 163void tick_install_broadcast_device(struct clock_event_device *dev, int cpu)
 164{
 165	struct clock_event_device *cur = tick_broadcast_device.evtdev;
 166
 167	if (tick_set_oneshot_wakeup_device(dev, cpu))
 168		return;
 169
 170	if (!tick_check_broadcast_device(cur, dev))
 171		return;
 172
 173	if (!try_module_get(dev->owner))
 174		return;
 175
 176	clockevents_exchange_device(cur, dev);
 177	if (cur)
 178		cur->event_handler = clockevents_handle_noop;
 179	tick_broadcast_device.evtdev = dev;
 180	if (!cpumask_empty(tick_broadcast_mask))
 181		tick_broadcast_start_periodic(dev);
 182
 183	if (!(dev->features & CLOCK_EVT_FEAT_ONESHOT))
 184		return;
 185
 186	/*
 187	 * If the system already runs in oneshot mode, switch the newly
 188	 * registered broadcast device to oneshot mode explicitly.
 189	 */
 190	if (tick_broadcast_oneshot_active()) {
 191		tick_broadcast_switch_to_oneshot();
 192		return;
 193	}
 194
 195	/*
 196	 * Inform all cpus about this. We might be in a situation
 197	 * where we did not switch to oneshot mode because the per cpu
 198	 * devices are affected by CLOCK_EVT_FEAT_C3STOP and the lack
 199	 * of a oneshot capable broadcast device. Without that
 200	 * notification the systems stays stuck in periodic mode
 201	 * forever.
 202	 */
 203	tick_clock_notify();
 204}
 205
 206/*
 207 * Check, if the device is the broadcast device
 208 */
 209int tick_is_broadcast_device(struct clock_event_device *dev)
 210{
 211	return (dev && tick_broadcast_device.evtdev == dev);
 212}
 213
 214int tick_broadcast_update_freq(struct clock_event_device *dev, u32 freq)
 215{
 216	int ret = -ENODEV;
 217
 218	if (tick_is_broadcast_device(dev)) {
 219		raw_spin_lock(&tick_broadcast_lock);
 220		ret = __clockevents_update_freq(dev, freq);
 221		raw_spin_unlock(&tick_broadcast_lock);
 222	}
 223	return ret;
 224}
 225
 226
 227static void err_broadcast(const struct cpumask *mask)
 228{
 229	pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
 230}
 231
 232static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
 233{
 234	if (!dev->broadcast)
 235		dev->broadcast = tick_broadcast;
 236	if (!dev->broadcast) {
 237		pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
 238			     dev->name);
 239		dev->broadcast = err_broadcast;
 240	}
 241}
 242
 243/*
 244 * Check, if the device is dysfunctional and a placeholder, which
 245 * needs to be handled by the broadcast device.
 246 */
 247int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
 248{
 249	struct clock_event_device *bc = tick_broadcast_device.evtdev;
 250	unsigned long flags;
 251	int ret = 0;
 252
 253	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 254
 255	/*
 256	 * Devices might be registered with both periodic and oneshot
 257	 * mode disabled. This signals, that the device needs to be
 258	 * operated from the broadcast device and is a placeholder for
 259	 * the cpu local device.
 260	 */
 261	if (!tick_device_is_functional(dev)) {
 262		dev->event_handler = tick_handle_periodic;
 263		tick_device_setup_broadcast_func(dev);
 264		cpumask_set_cpu(cpu, tick_broadcast_mask);
 265		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 266			tick_broadcast_start_periodic(bc);
 267		else
 268			tick_broadcast_setup_oneshot(bc, false);
 269		ret = 1;
 270	} else {
 271		/*
 272		 * Clear the broadcast bit for this cpu if the
 273		 * device is not power state affected.
 274		 */
 275		if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 276			cpumask_clear_cpu(cpu, tick_broadcast_mask);
 277		else
 278			tick_device_setup_broadcast_func(dev);
 279
 280		/*
 281		 * Clear the broadcast bit if the CPU is not in
 282		 * periodic broadcast on state.
 283		 */
 284		if (!cpumask_test_cpu(cpu, tick_broadcast_on))
 285			cpumask_clear_cpu(cpu, tick_broadcast_mask);
 286
 287		switch (tick_broadcast_device.mode) {
 288		case TICKDEV_MODE_ONESHOT:
 289			/*
 290			 * If the system is in oneshot mode we can
 291			 * unconditionally clear the oneshot mask bit,
 292			 * because the CPU is running and therefore
 293			 * not in an idle state which causes the power
 294			 * state affected device to stop. Let the
 295			 * caller initialize the device.
 296			 */
 297			tick_broadcast_clear_oneshot(cpu);
 298			ret = 0;
 299			break;
 300
 301		case TICKDEV_MODE_PERIODIC:
 302			/*
 303			 * If the system is in periodic mode, check
 304			 * whether the broadcast device can be
 305			 * switched off now.
 306			 */
 307			if (cpumask_empty(tick_broadcast_mask) && bc)
 308				clockevents_shutdown(bc);
 309			/*
 310			 * If we kept the cpu in the broadcast mask,
 311			 * tell the caller to leave the per cpu device
 312			 * in shutdown state. The periodic interrupt
 313			 * is delivered by the broadcast device, if
 314			 * the broadcast device exists and is not
 315			 * hrtimer based.
 316			 */
 317			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER))
 318				ret = cpumask_test_cpu(cpu, tick_broadcast_mask);
 319			break;
 320		default:
 321			break;
 322		}
 323	}
 324	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 325	return ret;
 326}
 327
 328int tick_receive_broadcast(void)
 329{
 330	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 331	struct clock_event_device *evt = td->evtdev;
 332
 333	if (!evt)
 334		return -ENODEV;
 335
 336	if (!evt->event_handler)
 337		return -EINVAL;
 338
 339	evt->event_handler(evt);
 340	return 0;
 341}
 342
 343/*
 344 * Broadcast the event to the cpus, which are set in the mask (mangled).
 345 */
 346static bool tick_do_broadcast(struct cpumask *mask)
 347{
 348	int cpu = smp_processor_id();
 349	struct tick_device *td;
 350	bool local = false;
 351
 352	/*
 353	 * Check, if the current cpu is in the mask
 354	 */
 355	if (cpumask_test_cpu(cpu, mask)) {
 356		struct clock_event_device *bc = tick_broadcast_device.evtdev;
 357
 358		cpumask_clear_cpu(cpu, mask);
 359		/*
 360		 * We only run the local handler, if the broadcast
 361		 * device is not hrtimer based. Otherwise we run into
 362		 * a hrtimer recursion.
 363		 *
 364		 * local timer_interrupt()
 365		 *   local_handler()
 366		 *     expire_hrtimers()
 367		 *       bc_handler()
 368		 *         local_handler()
 369		 *	     expire_hrtimers()
 370		 */
 371		local = !(bc->features & CLOCK_EVT_FEAT_HRTIMER);
 372	}
 373
 374	if (!cpumask_empty(mask)) {
 375		/*
 376		 * It might be necessary to actually check whether the devices
 377		 * have different broadcast functions. For now, just use the
 378		 * one of the first device. This works as long as we have this
 379		 * misfeature only on x86 (lapic)
 380		 */
 381		td = &per_cpu(tick_cpu_device, cpumask_first(mask));
 382		td->evtdev->broadcast(mask);
 383	}
 384	return local;
 385}
 386
 387/*
 388 * Periodic broadcast:
 389 * - invoke the broadcast handlers
 390 */
 391static bool tick_do_periodic_broadcast(void)
 392{
 393	cpumask_and(tmpmask, cpu_online_mask, tick_broadcast_mask);
 394	return tick_do_broadcast(tmpmask);
 
 
 
 
 
 395}
 396
 397/*
 398 * Event handler for periodic broadcast ticks
 399 */
 400static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 401{
 402	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 403	bool bc_local;
 404
 405	raw_spin_lock(&tick_broadcast_lock);
 406
 407	/* Handle spurious interrupts gracefully */
 408	if (clockevent_state_shutdown(tick_broadcast_device.evtdev)) {
 409		raw_spin_unlock(&tick_broadcast_lock);
 
 410		return;
 411	}
 412
 413	bc_local = tick_do_periodic_broadcast();
 414
 415	if (clockevent_state_oneshot(dev)) {
 416		ktime_t next = ktime_add_ns(dev->next_event, TICK_NSEC);
 417
 418		clockevents_program_event(dev, next, true);
 419	}
 420	raw_spin_unlock(&tick_broadcast_lock);
 421
 422	/*
 423	 * We run the handler of the local cpu after dropping
 424	 * tick_broadcast_lock because the handler might deadlock when
 425	 * trying to switch to oneshot mode.
 
 
 426	 */
 427	if (bc_local)
 428		td->evtdev->event_handler(td->evtdev);
 
 
 
 
 
 429}
 430
 431/**
 432 * tick_broadcast_control - Enable/disable or force broadcast mode
 433 * @mode:	The selected broadcast mode
 434 *
 435 * Called when the system enters a state where affected tick devices
 436 * might stop. Note: TICK_BROADCAST_FORCE cannot be undone.
 437 */
 438void tick_broadcast_control(enum tick_broadcast_mode mode)
 439{
 440	struct clock_event_device *bc, *dev;
 441	struct tick_device *td;
 442	int cpu, bc_stopped;
 443	unsigned long flags;
 
 444
 445	/* Protects also the local clockevent device. */
 446	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 447	td = this_cpu_ptr(&tick_cpu_device);
 
 
 448	dev = td->evtdev;
 
 449
 450	/*
 451	 * Is the device not affected by the powerstate ?
 452	 */
 453	if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
 454		goto out;
 455
 456	if (!tick_device_is_functional(dev))
 457		goto out;
 458
 459	cpu = smp_processor_id();
 460	bc = tick_broadcast_device.evtdev;
 461	bc_stopped = cpumask_empty(tick_broadcast_mask);
 462
 463	switch (mode) {
 464	case TICK_BROADCAST_FORCE:
 465		tick_broadcast_forced = 1;
 466		fallthrough;
 467	case TICK_BROADCAST_ON:
 468		cpumask_set_cpu(cpu, tick_broadcast_on);
 469		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_mask)) {
 470			/*
 471			 * Only shutdown the cpu local device, if:
 472			 *
 473			 * - the broadcast device exists
 474			 * - the broadcast device is not a hrtimer based one
 475			 * - the broadcast device is in periodic mode to
 476			 *   avoid a hiccup during switch to oneshot mode
 477			 */
 478			if (bc && !(bc->features & CLOCK_EVT_FEAT_HRTIMER) &&
 479			    tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 480				clockevents_shutdown(dev);
 481		}
 
 
 482		break;
 483
 484	case TICK_BROADCAST_OFF:
 485		if (tick_broadcast_forced)
 486			break;
 487		cpumask_clear_cpu(cpu, tick_broadcast_on);
 488		if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_mask)) {
 489			if (tick_broadcast_device.mode ==
 490			    TICKDEV_MODE_PERIODIC)
 491				tick_setup_periodic(dev, 0);
 492		}
 493		break;
 494	}
 495
 496	if (bc) {
 497		if (cpumask_empty(tick_broadcast_mask)) {
 498			if (!bc_stopped)
 499				clockevents_shutdown(bc);
 500		} else if (bc_stopped) {
 501			if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 502				tick_broadcast_start_periodic(bc);
 503			else
 504				tick_broadcast_setup_oneshot(bc, false);
 505		}
 506	}
 507out:
 508	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 509}
 510EXPORT_SYMBOL_GPL(tick_broadcast_control);
 
 
 
 
 
 
 
 
 
 
 
 
 511
 512/*
 513 * Set the periodic handler depending on broadcast on/off
 514 */
 515void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 516{
 517	if (!broadcast)
 518		dev->event_handler = tick_handle_periodic;
 519	else
 520		dev->event_handler = tick_handle_periodic_broadcast;
 521}
 522
 523#ifdef CONFIG_HOTPLUG_CPU
 524static void tick_shutdown_broadcast(void)
 
 
 525{
 526	struct clock_event_device *bc = tick_broadcast_device.evtdev;
 
 
 
 
 
 
 
 527
 528	if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 529		if (bc && cpumask_empty(tick_broadcast_mask))
 530			clockevents_shutdown(bc);
 531	}
 532}
 533
 534/*
 535 * Remove a CPU from broadcasting
 536 */
 537void tick_broadcast_offline(unsigned int cpu)
 538{
 539	raw_spin_lock(&tick_broadcast_lock);
 540	cpumask_clear_cpu(cpu, tick_broadcast_mask);
 541	cpumask_clear_cpu(cpu, tick_broadcast_on);
 542	tick_broadcast_oneshot_offline(cpu);
 543	tick_shutdown_broadcast();
 544	raw_spin_unlock(&tick_broadcast_lock);
 545}
 546
 547#endif
 548
 549void tick_suspend_broadcast(void)
 550{
 551	struct clock_event_device *bc;
 552	unsigned long flags;
 553
 554	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 555
 556	bc = tick_broadcast_device.evtdev;
 557	if (bc)
 558		clockevents_shutdown(bc);
 559
 560	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 561}
 562
 563/*
 564 * This is called from tick_resume_local() on a resuming CPU. That's
 565 * called from the core resume function, tick_unfreeze() and the magic XEN
 566 * resume hackery.
 567 *
 568 * In none of these cases the broadcast device mode can change and the
 569 * bit of the resuming CPU in the broadcast mask is safe as well.
 570 */
 571bool tick_resume_check_broadcast(void)
 572{
 573	if (tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT)
 574		return false;
 575	else
 576		return cpumask_test_cpu(smp_processor_id(), tick_broadcast_mask);
 577}
 578
 579void tick_resume_broadcast(void)
 580{
 581	struct clock_event_device *bc;
 582	unsigned long flags;
 
 583
 584	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 585
 586	bc = tick_broadcast_device.evtdev;
 587
 588	if (bc) {
 589		clockevents_tick_resume(bc);
 590
 591		switch (tick_broadcast_device.mode) {
 592		case TICKDEV_MODE_PERIODIC:
 593			if (!cpumask_empty(tick_broadcast_mask))
 594				tick_broadcast_start_periodic(bc);
 
 
 595			break;
 596		case TICKDEV_MODE_ONESHOT:
 597			if (!cpumask_empty(tick_broadcast_mask))
 598				tick_resume_broadcast_oneshot(bc);
 599			break;
 600		}
 601	}
 602	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 
 
 603}
 604
 
 605#ifdef CONFIG_TICK_ONESHOT
 606
 607static cpumask_var_t tick_broadcast_oneshot_mask __cpumask_var_read_mostly;
 608static cpumask_var_t tick_broadcast_pending_mask __cpumask_var_read_mostly;
 609static cpumask_var_t tick_broadcast_force_mask __cpumask_var_read_mostly;
 610
 611/*
 612 * Exposed for debugging: see timer_list.c
 613 */
 614struct cpumask *tick_get_broadcast_oneshot_mask(void)
 615{
 616	return tick_broadcast_oneshot_mask;
 617}
 618
 619/*
 620 * Called before going idle with interrupts disabled. Checks whether a
 621 * broadcast event from the other core is about to happen. We detected
 622 * that in tick_broadcast_oneshot_control(). The callsite can use this
 623 * to avoid a deep idle transition as we are about to get the
 624 * broadcast IPI right away.
 625 */
 626noinstr int tick_check_broadcast_expired(void)
 627{
 628#ifdef _ASM_GENERIC_BITOPS_INSTRUMENTED_NON_ATOMIC_H
 629	return arch_test_bit(smp_processor_id(), cpumask_bits(tick_broadcast_force_mask));
 630#else
 631	return cpumask_test_cpu(smp_processor_id(), tick_broadcast_force_mask);
 632#endif
 633}
 634
 635/*
 636 * Set broadcast interrupt affinity
 637 */
 638static void tick_broadcast_set_affinity(struct clock_event_device *bc,
 639					const struct cpumask *cpumask)
 640{
 641	if (!(bc->features & CLOCK_EVT_FEAT_DYNIRQ))
 642		return;
 643
 644	if (cpumask_equal(bc->cpumask, cpumask))
 645		return;
 646
 647	bc->cpumask = cpumask;
 648	irq_set_affinity(bc->irq, bc->cpumask);
 649}
 650
 651static void tick_broadcast_set_event(struct clock_event_device *bc, int cpu,
 652				     ktime_t expires)
 653{
 654	if (!clockevent_state_oneshot(bc))
 655		clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
 656
 657	clockevents_program_event(bc, expires, 1);
 658	tick_broadcast_set_affinity(bc, cpumask_of(cpu));
 659}
 660
 661static void tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 662{
 663	clockevents_switch_state(bc, CLOCK_EVT_STATE_ONESHOT);
 
 664}
 665
 666/*
 667 * Called from irq_enter() when idle was interrupted to reenable the
 668 * per cpu device.
 669 */
 670void tick_check_oneshot_broadcast_this_cpu(void)
 671{
 672	if (cpumask_test_cpu(smp_processor_id(), tick_broadcast_oneshot_mask)) {
 673		struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 674
 675		/*
 676		 * We might be in the middle of switching over from
 677		 * periodic to oneshot. If the CPU has not yet
 678		 * switched over, leave the device alone.
 679		 */
 680		if (td->mode == TICKDEV_MODE_ONESHOT) {
 681			clockevents_switch_state(td->evtdev,
 682					      CLOCK_EVT_STATE_ONESHOT);
 683		}
 684	}
 685}
 686
 687/*
 688 * Handle oneshot mode broadcasting
 689 */
 690static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 691{
 692	struct tick_device *td;
 693	ktime_t now, next_event;
 694	int cpu, next_cpu = 0;
 695	bool bc_local;
 696
 697	raw_spin_lock(&tick_broadcast_lock);
 698	dev->next_event = KTIME_MAX;
 699	next_event = KTIME_MAX;
 700	cpumask_clear(tmpmask);
 
 701	now = ktime_get();
 702	/* Find all expired events */
 703	for_each_cpu(cpu, tick_broadcast_oneshot_mask) {
 704		/*
 705		 * Required for !SMP because for_each_cpu() reports
 706		 * unconditionally CPU0 as set on UP kernels.
 707		 */
 708		if (!IS_ENABLED(CONFIG_SMP) &&
 709		    cpumask_empty(tick_broadcast_oneshot_mask))
 710			break;
 711
 712		td = &per_cpu(tick_cpu_device, cpu);
 713		if (td->evtdev->next_event <= now) {
 714			cpumask_set_cpu(cpu, tmpmask);
 715			/*
 716			 * Mark the remote cpu in the pending mask, so
 717			 * it can avoid reprogramming the cpu local
 718			 * timer in tick_broadcast_oneshot_control().
 719			 */
 720			cpumask_set_cpu(cpu, tick_broadcast_pending_mask);
 721		} else if (td->evtdev->next_event < next_event) {
 722			next_event = td->evtdev->next_event;
 723			next_cpu = cpu;
 724		}
 725	}
 726
 727	/*
 728	 * Remove the current cpu from the pending mask. The event is
 729	 * delivered immediately in tick_do_broadcast() !
 730	 */
 731	cpumask_clear_cpu(smp_processor_id(), tick_broadcast_pending_mask);
 732
 733	/* Take care of enforced broadcast requests */
 734	cpumask_or(tmpmask, tmpmask, tick_broadcast_force_mask);
 735	cpumask_clear(tick_broadcast_force_mask);
 736
 737	/*
 738	 * Sanity check. Catch the case where we try to broadcast to
 739	 * offline cpus.
 740	 */
 741	if (WARN_ON_ONCE(!cpumask_subset(tmpmask, cpu_online_mask)))
 742		cpumask_and(tmpmask, tmpmask, cpu_online_mask);
 743
 744	/*
 745	 * Wakeup the cpus which have an expired event.
 746	 */
 747	bc_local = tick_do_broadcast(tmpmask);
 748
 749	/*
 750	 * Two reasons for reprogram:
 751	 *
 752	 * - The global event did not expire any CPU local
 753	 * events. This happens in dyntick mode, as the maximum PIT
 754	 * delta is quite small.
 755	 *
 756	 * - There are pending events on sleeping CPUs which were not
 757	 * in the event mask
 758	 */
 759	if (next_event != KTIME_MAX)
 760		tick_broadcast_set_event(dev, next_cpu, next_event);
 761
 762	raw_spin_unlock(&tick_broadcast_lock);
 763
 764	if (bc_local) {
 765		td = this_cpu_ptr(&tick_cpu_device);
 766		td->evtdev->event_handler(td->evtdev);
 767	}
 
 768}
 769
 770static int broadcast_needs_cpu(struct clock_event_device *bc, int cpu)
 
 
 
 
 771{
 772	if (!(bc->features & CLOCK_EVT_FEAT_HRTIMER))
 773		return 0;
 774	if (bc->next_event == KTIME_MAX)
 775		return 0;
 776	return bc->bound_on == cpu ? -EBUSY : 0;
 777}
 778
 779static void broadcast_shutdown_local(struct clock_event_device *bc,
 780				     struct clock_event_device *dev)
 781{
 782	/*
 783	 * For hrtimer based broadcasting we cannot shutdown the cpu
 784	 * local device if our own event is the first one to expire or
 785	 * if we own the broadcast timer.
 786	 */
 787	if (bc->features & CLOCK_EVT_FEAT_HRTIMER) {
 788		if (broadcast_needs_cpu(bc, smp_processor_id()))
 789			return;
 790		if (dev->next_event < bc->next_event)
 791			return;
 792	}
 793	clockevents_switch_state(dev, CLOCK_EVT_STATE_SHUTDOWN);
 794}
 795
 796static int ___tick_broadcast_oneshot_control(enum tick_broadcast_state state,
 797					     struct tick_device *td,
 798					     int cpu)
 799{
 800	struct clock_event_device *bc, *dev = td->evtdev;
 801	int ret = 0;
 802	ktime_t now;
 803
 804	raw_spin_lock(&tick_broadcast_lock);
 805	bc = tick_broadcast_device.evtdev;
 806
 807	if (state == TICK_BROADCAST_ENTER) {
 808		/*
 809		 * If the current CPU owns the hrtimer broadcast
 810		 * mechanism, it cannot go deep idle and we do not add
 811		 * the CPU to the broadcast mask. We don't have to go
 812		 * through the EXIT path as the local timer is not
 813		 * shutdown.
 814		 */
 815		ret = broadcast_needs_cpu(bc, cpu);
 816		if (ret)
 817			goto out;
 818
 819		/*
 820		 * If the broadcast device is in periodic mode, we
 821		 * return.
 822		 */
 823		if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 824			/* If it is a hrtimer based broadcast, return busy */
 825			if (bc->features & CLOCK_EVT_FEAT_HRTIMER)
 826				ret = -EBUSY;
 827			goto out;
 828		}
 829
 830		if (!cpumask_test_and_set_cpu(cpu, tick_broadcast_oneshot_mask)) {
 831			WARN_ON_ONCE(cpumask_test_cpu(cpu, tick_broadcast_pending_mask));
 832
 833			/* Conditionally shut down the local timer. */
 834			broadcast_shutdown_local(bc, dev);
 835
 836			/*
 837			 * We only reprogram the broadcast timer if we
 838			 * did not mark ourself in the force mask and
 839			 * if the cpu local event is earlier than the
 840			 * broadcast event. If the current CPU is in
 841			 * the force mask, then we are going to be
 842			 * woken by the IPI right away; we return
 843			 * busy, so the CPU does not try to go deep
 844			 * idle.
 845			 */
 846			if (cpumask_test_cpu(cpu, tick_broadcast_force_mask)) {
 847				ret = -EBUSY;
 848			} else if (dev->next_event < bc->next_event) {
 849				tick_broadcast_set_event(bc, cpu, dev->next_event);
 850				/*
 851				 * In case of hrtimer broadcasts the
 852				 * programming might have moved the
 853				 * timer to this cpu. If yes, remove
 854				 * us from the broadcast mask and
 855				 * return busy.
 856				 */
 857				ret = broadcast_needs_cpu(bc, cpu);
 858				if (ret) {
 859					cpumask_clear_cpu(cpu,
 860						tick_broadcast_oneshot_mask);
 861				}
 862			}
 863		}
 864	} else {
 865		if (cpumask_test_and_clear_cpu(cpu, tick_broadcast_oneshot_mask)) {
 866			clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT);
 867			/*
 868			 * The cpu which was handling the broadcast
 869			 * timer marked this cpu in the broadcast
 870			 * pending mask and fired the broadcast
 871			 * IPI. So we are going to handle the expired
 872			 * event anyway via the broadcast IPI
 873			 * handler. No need to reprogram the timer
 874			 * with an already expired event.
 875			 */
 876			if (cpumask_test_and_clear_cpu(cpu,
 877				       tick_broadcast_pending_mask))
 878				goto out;
 879
 880			/*
 881			 * Bail out if there is no next event.
 882			 */
 883			if (dev->next_event == KTIME_MAX)
 884				goto out;
 885			/*
 886			 * If the pending bit is not set, then we are
 887			 * either the CPU handling the broadcast
 888			 * interrupt or we got woken by something else.
 889			 *
 890			 * We are no longer in the broadcast mask, so
 891			 * if the cpu local expiry time is already
 892			 * reached, we would reprogram the cpu local
 893			 * timer with an already expired event.
 894			 *
 895			 * This can lead to a ping-pong when we return
 896			 * to idle and therefore rearm the broadcast
 897			 * timer before the cpu local timer was able
 898			 * to fire. This happens because the forced
 899			 * reprogramming makes sure that the event
 900			 * will happen in the future and depending on
 901			 * the min_delta setting this might be far
 902			 * enough out that the ping-pong starts.
 903			 *
 904			 * If the cpu local next_event has expired
 905			 * then we know that the broadcast timer
 906			 * next_event has expired as well and
 907			 * broadcast is about to be handled. So we
 908			 * avoid reprogramming and enforce that the
 909			 * broadcast handler, which did not run yet,
 910			 * will invoke the cpu local handler.
 911			 *
 912			 * We cannot call the handler directly from
 913			 * here, because we might be in a NOHZ phase
 914			 * and we did not go through the irq_enter()
 915			 * nohz fixups.
 916			 */
 917			now = ktime_get();
 918			if (dev->next_event <= now) {
 919				cpumask_set_cpu(cpu, tick_broadcast_force_mask);
 920				goto out;
 921			}
 922			/*
 923			 * We got woken by something else. Reprogram
 924			 * the cpu local timer device.
 925			 */
 926			tick_program_event(dev->next_event, 1);
 927		}
 928	}
 929out:
 930	raw_spin_unlock(&tick_broadcast_lock);
 931	return ret;
 932}
 933
 934static int tick_oneshot_wakeup_control(enum tick_broadcast_state state,
 935				       struct tick_device *td,
 936				       int cpu)
 937{
 938	struct clock_event_device *dev, *wd;
 939
 940	dev = td->evtdev;
 941	if (td->mode != TICKDEV_MODE_ONESHOT)
 942		return -EINVAL;
 943
 944	wd = tick_get_oneshot_wakeup_device(cpu);
 945	if (!wd)
 946		return -ENODEV;
 947
 948	switch (state) {
 949	case TICK_BROADCAST_ENTER:
 950		clockevents_switch_state(dev, CLOCK_EVT_STATE_ONESHOT_STOPPED);
 951		clockevents_switch_state(wd, CLOCK_EVT_STATE_ONESHOT);
 952		clockevents_program_event(wd, dev->next_event, 1);
 953		break;
 954	case TICK_BROADCAST_EXIT:
 955		/* We may have transitioned to oneshot mode while idle */
 956		if (clockevent_get_state(wd) != CLOCK_EVT_STATE_ONESHOT)
 957			return -ENODEV;
 958	}
 959
 960	return 0;
 961}
 962
 963int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
 964{
 965	struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 966	int cpu = smp_processor_id();
 967
 968	if (!tick_oneshot_wakeup_control(state, td, cpu))
 969		return 0;
 970
 971	if (tick_broadcast_device.evtdev)
 972		return ___tick_broadcast_oneshot_control(state, td, cpu);
 973
 974	/*
 975	 * If there is no broadcast or wakeup device, tell the caller not
 976	 * to go into deep idle.
 977	 */
 978	return -EBUSY;
 979}
 980
 981/*
 982 * Reset the one shot broadcast for a cpu
 983 *
 984 * Called with tick_broadcast_lock held
 985 */
 986static void tick_broadcast_clear_oneshot(int cpu)
 987{
 988	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
 989	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
 990}
 991
 992static void tick_broadcast_init_next_event(struct cpumask *mask,
 993					   ktime_t expires)
 994{
 995	struct tick_device *td;
 996	int cpu;
 997
 998	for_each_cpu(cpu, mask) {
 999		td = &per_cpu(tick_cpu_device, cpu);
1000		if (td->evtdev)
1001			td->evtdev->next_event = expires;
1002	}
1003}
1004
1005static inline ktime_t tick_get_next_period(void)
1006{
1007	ktime_t next;
1008
1009	/*
1010	 * Protect against concurrent updates (store /load tearing on
1011	 * 32bit). It does not matter if the time is already in the
1012	 * past. The broadcast device which is about to be programmed will
1013	 * fire in any case.
1014	 */
1015	raw_spin_lock(&jiffies_lock);
1016	next = tick_next_period;
1017	raw_spin_unlock(&jiffies_lock);
1018	return next;
1019}
1020
1021/**
1022 * tick_broadcast_setup_oneshot - setup the broadcast device
1023 */
1024static void tick_broadcast_setup_oneshot(struct clock_event_device *bc,
1025					 bool from_periodic)
1026{
1027	int cpu = smp_processor_id();
1028	ktime_t nexttick = 0;
1029
1030	if (!bc)
1031		return;
1032
1033	/*
1034	 * When the broadcast device was switched to oneshot by the first
1035	 * CPU handling the NOHZ change, the other CPUs will reach this
1036	 * code via hrtimer_run_queues() -> tick_check_oneshot_change()
1037	 * too. Set up the broadcast device only once!
1038	 */
1039	if (bc->event_handler == tick_handle_oneshot_broadcast) {
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 
1040		/*
1041		 * The CPU which switched from periodic to oneshot mode
1042		 * set the broadcast oneshot bit for all other CPUs which
1043		 * are in the general (periodic) broadcast mask to ensure
1044		 * that CPUs which wait for the periodic broadcast are
1045		 * woken up.
1046		 *
1047		 * Clear the bit for the local CPU as the set bit would
1048		 * prevent the first tick_broadcast_enter() after this CPU
1049		 * switched to oneshot state to program the broadcast
1050		 * device.
1051		 *
1052		 * This code can also be reached via tick_broadcast_control(),
1053		 * but this cannot avoid the tick_broadcast_clear_oneshot()
1054		 * as that would break the periodic to oneshot transition of
1055		 * secondary CPUs. But that's harmless as the below only
1056		 * clears already cleared bits.
1057		 */
1058		tick_broadcast_clear_oneshot(cpu);
1059		return;
1060	}
1061
1062
1063	bc->event_handler = tick_handle_oneshot_broadcast;
1064	bc->next_event = KTIME_MAX;
1065
1066	/*
1067	 * When the tick mode is switched from periodic to oneshot it must
1068	 * be ensured that CPUs which are waiting for periodic broadcast
1069	 * get their wake-up at the next tick.  This is achieved by ORing
1070	 * tick_broadcast_mask into tick_broadcast_oneshot_mask.
1071	 *
1072	 * For other callers, e.g. broadcast device replacement,
1073	 * tick_broadcast_oneshot_mask must not be touched as this would
1074	 * set bits for CPUs which are already NOHZ, but not idle. Their
1075	 * next tick_broadcast_enter() would observe the bit set and fail
1076	 * to update the expiry time and the broadcast event device.
1077	 */
1078	if (from_periodic) {
1079		cpumask_copy(tmpmask, tick_broadcast_mask);
1080		/* Remove the local CPU as it is obviously not idle */
1081		cpumask_clear_cpu(cpu, tmpmask);
1082		cpumask_or(tick_broadcast_oneshot_mask, tick_broadcast_oneshot_mask, tmpmask);
1083
1084		/*
1085		 * Ensure that the oneshot broadcast handler will wake the
1086		 * CPUs which are still waiting for periodic broadcast.
1087		 */
1088		nexttick = tick_get_next_period();
1089		tick_broadcast_init_next_event(tmpmask, nexttick);
1090
1091		/*
1092		 * If the underlying broadcast clock event device is
1093		 * already in oneshot state, then there is nothing to do.
1094		 * The device was already armed for the next tick
1095		 * in tick_handle_broadcast_periodic()
1096		 */
1097		if (clockevent_state_oneshot(bc))
1098			return;
1099	}
1100
1101	/*
1102	 * When switching from periodic to oneshot mode arm the broadcast
1103	 * device for the next tick.
1104	 *
1105	 * If the broadcast device has been replaced in oneshot mode and
1106	 * the oneshot broadcast mask is not empty, then arm it to expire
1107	 * immediately in order to reevaluate the next expiring timer.
1108	 * @nexttick is 0 and therefore in the past which will cause the
1109	 * clockevent code to force an event.
1110	 *
1111	 * For both cases the programming can be avoided when the oneshot
1112	 * broadcast mask is empty.
1113	 *
1114	 * tick_broadcast_set_event() implicitly switches the broadcast
1115	 * device to oneshot state.
1116	 */
1117	if (!cpumask_empty(tick_broadcast_oneshot_mask))
1118		tick_broadcast_set_event(bc, cpu, nexttick);
1119}
1120
1121/*
1122 * Select oneshot operating mode for the broadcast device
1123 */
1124void tick_broadcast_switch_to_oneshot(void)
1125{
1126	struct clock_event_device *bc;
1127	enum tick_device_mode oldmode;
1128	unsigned long flags;
1129
1130	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
1131
1132	oldmode = tick_broadcast_device.mode;
1133	tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
1134	bc = tick_broadcast_device.evtdev;
1135	if (bc)
1136		tick_broadcast_setup_oneshot(bc, oldmode == TICKDEV_MODE_PERIODIC);
1137
1138	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
1139}
1140
1141#ifdef CONFIG_HOTPLUG_CPU
1142void hotplug_cpu__broadcast_tick_pull(int deadcpu)
1143{
1144	struct clock_event_device *bc;
1145	unsigned long flags;
1146
1147	raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
1148	bc = tick_broadcast_device.evtdev;
1149
1150	if (bc && broadcast_needs_cpu(bc, deadcpu)) {
1151		/* This moves the broadcast assignment to this CPU: */
1152		clockevents_program_event(bc, bc->next_event, 1);
1153	}
1154	raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
1155}
1156
1157/*
1158 * Remove a dying CPU from broadcasting
1159 */
1160static void tick_broadcast_oneshot_offline(unsigned int cpu)
1161{
1162	if (tick_get_oneshot_wakeup_device(cpu))
1163		tick_set_oneshot_wakeup_device(NULL, cpu);
 
 
1164
1165	/*
1166	 * Clear the broadcast masks for the dead cpu, but do not stop
1167	 * the broadcast device!
1168	 */
1169	cpumask_clear_cpu(cpu, tick_broadcast_oneshot_mask);
1170	cpumask_clear_cpu(cpu, tick_broadcast_pending_mask);
1171	cpumask_clear_cpu(cpu, tick_broadcast_force_mask);
1172}
1173#endif
1174
1175/*
1176 * Check, whether the broadcast device is in one shot mode
1177 */
1178int tick_broadcast_oneshot_active(void)
1179{
1180	return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
1181}
1182
1183/*
1184 * Check whether the broadcast device supports oneshot.
1185 */
1186bool tick_broadcast_oneshot_available(void)
1187{
1188	struct clock_event_device *bc = tick_broadcast_device.evtdev;
1189
1190	return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
1191}
1192
1193#else
1194int __tick_broadcast_oneshot_control(enum tick_broadcast_state state)
1195{
1196	struct clock_event_device *bc = tick_broadcast_device.evtdev;
1197
1198	if (!bc || (bc->features & CLOCK_EVT_FEAT_HRTIMER))
1199		return -EBUSY;
1200
1201	return 0;
1202}
1203#endif
1204
1205void __init tick_broadcast_init(void)
1206{
1207	zalloc_cpumask_var(&tick_broadcast_mask, GFP_NOWAIT);
1208	zalloc_cpumask_var(&tick_broadcast_on, GFP_NOWAIT);
1209	zalloc_cpumask_var(&tmpmask, GFP_NOWAIT);
1210#ifdef CONFIG_TICK_ONESHOT
1211	zalloc_cpumask_var(&tick_broadcast_oneshot_mask, GFP_NOWAIT);
1212	zalloc_cpumask_var(&tick_broadcast_pending_mask, GFP_NOWAIT);
1213	zalloc_cpumask_var(&tick_broadcast_force_mask, GFP_NOWAIT);
1214#endif
1215}