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