linux/kernel/time/tick-broadcast.c
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   1/*
   2 * linux/kernel/time/tick-broadcast.c
   3 *
   4 * This file contains functions which emulate a local clock-event
   5 * device via a broadcast event source.
   6 *
   7 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
   8 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
   9 * Copyright(C) 2006-2007, Timesys Corp., Thomas Gleixner
  10 *
  11 * This code is licenced under the GPL version 2. For details see
  12 * kernel-base/COPYING.
  13 */
  14#include <linux/cpu.h>
  15#include <linux/err.h>
  16#include <linux/hrtimer.h>
  17#include <linux/interrupt.h>
  18#include <linux/percpu.h>
  19#include <linux/profile.h>
  20#include <linux/sched.h>
  21
  22#include "tick-internal.h"
  23
  24/*
  25 * Broadcast support for broken x86 hardware, where the local apic
  26 * timer stops in C3 state.
  27 */
  28
  29static struct tick_device tick_broadcast_device;
  30/* FIXME: Use cpumask_var_t. */
  31static DECLARE_BITMAP(tick_broadcast_mask, NR_CPUS);
  32static DECLARE_BITMAP(tmpmask, NR_CPUS);
  33static DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
  34static int tick_broadcast_force;
  35
  36#ifdef CONFIG_TICK_ONESHOT
  37static void tick_broadcast_clear_oneshot(int cpu);
  38#else
  39static inline void tick_broadcast_clear_oneshot(int cpu) { }
  40#endif
  41
  42/*
  43 * Debugging: see timer_list.c
  44 */
  45struct tick_device *tick_get_broadcast_device(void)
  46{
  47        return &tick_broadcast_device;
  48}
  49
  50struct cpumask *tick_get_broadcast_mask(void)
  51{
  52        return to_cpumask(tick_broadcast_mask);
  53}
  54
  55/*
  56 * Start the device in periodic mode
  57 */
  58static void tick_broadcast_start_periodic(struct clock_event_device *bc)
  59{
  60        if (bc)
  61                tick_setup_periodic(bc, 1);
  62}
  63
  64/*
  65 * Check, if the device can be utilized as broadcast device:
  66 */
  67int tick_check_broadcast_device(struct clock_event_device *dev)
  68{
  69        if ((tick_broadcast_device.evtdev &&
  70             tick_broadcast_device.evtdev->rating >= dev->rating) ||
  71             (dev->features & CLOCK_EVT_FEAT_C3STOP))
  72                return 0;
  73
  74        clockevents_exchange_device(tick_broadcast_device.evtdev, dev);
  75        tick_broadcast_device.evtdev = dev;
  76        if (!cpumask_empty(tick_get_broadcast_mask()))
  77                tick_broadcast_start_periodic(dev);
  78        return 1;
  79}
  80
  81/*
  82 * Check, if the device is the broadcast device
  83 */
  84int tick_is_broadcast_device(struct clock_event_device *dev)
  85{
  86        return (dev && tick_broadcast_device.evtdev == dev);
  87}
  88
  89/*
  90 * Check, if the device is disfunctional and a place holder, which
  91 * needs to be handled by the broadcast device.
  92 */
  93int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
  94{
  95        unsigned long flags;
  96        int ret = 0;
  97
  98        raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
  99
 100        /*
 101         * Devices might be registered with both periodic and oneshot
 102         * mode disabled. This signals, that the device needs to be
 103         * operated from the broadcast device and is a placeholder for
 104         * the cpu local device.
 105         */
 106        if (!tick_device_is_functional(dev)) {
 107                dev->event_handler = tick_handle_periodic;
 108                cpumask_set_cpu(cpu, tick_get_broadcast_mask());
 109                tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
 110                ret = 1;
 111        } else {
 112                /*
 113                 * When the new device is not affected by the stop
 114                 * feature and the cpu is marked in the broadcast mask
 115                 * then clear the broadcast bit.
 116                 */
 117                if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) {
 118                        int cpu = smp_processor_id();
 119
 120                        cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
 121                        tick_broadcast_clear_oneshot(cpu);
 122                }
 123        }
 124        raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 125        return ret;
 126}
 127
 128/*
 129 * Broadcast the event to the cpus, which are set in the mask (mangled).
 130 */
 131static void tick_do_broadcast(struct cpumask *mask)
 132{
 133        int cpu = smp_processor_id();
 134        struct tick_device *td;
 135
 136        /*
 137         * Check, if the current cpu is in the mask
 138         */
 139        if (cpumask_test_cpu(cpu, mask)) {
 140                cpumask_clear_cpu(cpu, mask);
 141                td = &per_cpu(tick_cpu_device, cpu);
 142                td->evtdev->event_handler(td->evtdev);
 143        }
 144
 145        if (!cpumask_empty(mask)) {
 146                /*
 147                 * It might be necessary to actually check whether the devices
 148                 * have different broadcast functions. For now, just use the
 149                 * one of the first device. This works as long as we have this
 150                 * misfeature only on x86 (lapic)
 151                 */
 152                td = &per_cpu(tick_cpu_device, cpumask_first(mask));
 153                td->evtdev->broadcast(mask);
 154        }
 155}
 156
 157/*
 158 * Periodic broadcast:
 159 * - invoke the broadcast handlers
 160 */
 161static void tick_do_periodic_broadcast(void)
 162{
 163        raw_spin_lock(&tick_broadcast_lock);
 164
 165        cpumask_and(to_cpumask(tmpmask),
 166                    cpu_online_mask, tick_get_broadcast_mask());
 167        tick_do_broadcast(to_cpumask(tmpmask));
 168
 169        raw_spin_unlock(&tick_broadcast_lock);
 170}
 171
 172/*
 173 * Event handler for periodic broadcast ticks
 174 */
 175static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 176{
 177        ktime_t next;
 178
 179        tick_do_periodic_broadcast();
 180
 181        /*
 182         * The device is in periodic mode. No reprogramming necessary:
 183         */
 184        if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
 185                return;
 186
 187        /*
 188         * Setup the next period for devices, which do not have
 189         * periodic mode. We read dev->next_event first and add to it
 190         * when the event already expired. clockevents_program_event()
 191         * sets dev->next_event only when the event is really
 192         * programmed to the device.
 193         */
 194        for (next = dev->next_event; ;) {
 195                next = ktime_add(next, tick_period);
 196
 197                if (!clockevents_program_event(dev, next, false))
 198                        return;
 199                tick_do_periodic_broadcast();
 200        }
 201}
 202
 203/*
 204 * Powerstate information: The system enters/leaves a state, where
 205 * affected devices might stop
 206 */
 207static void tick_do_broadcast_on_off(unsigned long *reason)
 208{
 209        struct clock_event_device *bc, *dev;
 210        struct tick_device *td;
 211        unsigned long flags;
 212        int cpu, bc_stopped;
 213
 214        raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 215
 216        cpu = smp_processor_id();
 217        td = &per_cpu(tick_cpu_device, cpu);
 218        dev = td->evtdev;
 219        bc = tick_broadcast_device.evtdev;
 220
 221        /*
 222         * Is the device not affected by the powerstate ?
 223         */
 224        if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
 225                goto out;
 226
 227        if (!tick_device_is_functional(dev))
 228                goto out;
 229
 230        bc_stopped = cpumask_empty(tick_get_broadcast_mask());
 231
 232        switch (*reason) {
 233        case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 234        case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 235                if (!cpumask_test_cpu(cpu, tick_get_broadcast_mask())) {
 236                        cpumask_set_cpu(cpu, tick_get_broadcast_mask());
 237                        if (tick_broadcast_device.mode ==
 238                            TICKDEV_MODE_PERIODIC)
 239                                clockevents_shutdown(dev);
 240                }
 241                if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
 242                        tick_broadcast_force = 1;
 243                break;
 244        case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 245                if (!tick_broadcast_force &&
 246                    cpumask_test_cpu(cpu, tick_get_broadcast_mask())) {
 247                        cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
 248                        if (tick_broadcast_device.mode ==
 249                            TICKDEV_MODE_PERIODIC)
 250                                tick_setup_periodic(dev, 0);
 251                }
 252                break;
 253        }
 254
 255        if (cpumask_empty(tick_get_broadcast_mask())) {
 256                if (!bc_stopped)
 257                        clockevents_shutdown(bc);
 258        } else if (bc_stopped) {
 259                if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 260                        tick_broadcast_start_periodic(bc);
 261                else
 262                        tick_broadcast_setup_oneshot(bc);
 263        }
 264out:
 265        raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 266}
 267
 268/*
 269 * Powerstate information: The system enters/leaves a state, where
 270 * affected devices might stop.
 271 */
 272void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 273{
 274        if (!cpumask_test_cpu(*oncpu, cpu_online_mask))
 275                printk(KERN_ERR "tick-broadcast: ignoring broadcast for "
 276                       "offline CPU #%d\n", *oncpu);
 277        else
 278                tick_do_broadcast_on_off(&reason);
 279}
 280
 281/*
 282 * Set the periodic handler depending on broadcast on/off
 283 */
 284void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 285{
 286        if (!broadcast)
 287                dev->event_handler = tick_handle_periodic;
 288        else
 289                dev->event_handler = tick_handle_periodic_broadcast;
 290}
 291
 292/*
 293 * Remove a CPU from broadcasting
 294 */
 295void tick_shutdown_broadcast(unsigned int *cpup)
 296{
 297        struct clock_event_device *bc;
 298        unsigned long flags;
 299        unsigned int cpu = *cpup;
 300
 301        raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 302
 303        bc = tick_broadcast_device.evtdev;
 304        cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
 305
 306        if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 307                if (bc && cpumask_empty(tick_get_broadcast_mask()))
 308                        clockevents_shutdown(bc);
 309        }
 310
 311        raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 312}
 313
 314void tick_suspend_broadcast(void)
 315{
 316        struct clock_event_device *bc;
 317        unsigned long flags;
 318
 319        raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 320
 321        bc = tick_broadcast_device.evtdev;
 322        if (bc)
 323                clockevents_shutdown(bc);
 324
 325        raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 326}
 327
 328int tick_resume_broadcast(void)
 329{
 330        struct clock_event_device *bc;
 331        unsigned long flags;
 332        int broadcast = 0;
 333
 334        raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 335
 336        bc = tick_broadcast_device.evtdev;
 337
 338        if (bc) {
 339                clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
 340
 341                switch (tick_broadcast_device.mode) {
 342                case TICKDEV_MODE_PERIODIC:
 343                        if (!cpumask_empty(tick_get_broadcast_mask()))
 344                                tick_broadcast_start_periodic(bc);
 345                        broadcast = cpumask_test_cpu(smp_processor_id(),
 346                                                     tick_get_broadcast_mask());
 347                        break;
 348                case TICKDEV_MODE_ONESHOT:
 349                        if (!cpumask_empty(tick_get_broadcast_mask()))
 350                                broadcast = tick_resume_broadcast_oneshot(bc);
 351                        break;
 352                }
 353        }
 354        raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 355
 356        return broadcast;
 357}
 358
 359
 360#ifdef CONFIG_TICK_ONESHOT
 361
 362/* FIXME: use cpumask_var_t. */
 363static DECLARE_BITMAP(tick_broadcast_oneshot_mask, NR_CPUS);
 364
 365/*
 366 * Exposed for debugging: see timer_list.c
 367 */
 368struct cpumask *tick_get_broadcast_oneshot_mask(void)
 369{
 370        return to_cpumask(tick_broadcast_oneshot_mask);
 371}
 372
 373static int tick_broadcast_set_event(ktime_t expires, int force)
 374{
 375        struct clock_event_device *bc = tick_broadcast_device.evtdev;
 376
 377        if (bc->mode != CLOCK_EVT_MODE_ONESHOT)
 378                clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 379
 380        return clockevents_program_event(bc, expires, force);
 381}
 382
 383int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 384{
 385        clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 386        return 0;
 387}
 388
 389/*
 390 * Called from irq_enter() when idle was interrupted to reenable the
 391 * per cpu device.
 392 */
 393void tick_check_oneshot_broadcast(int cpu)
 394{
 395        if (cpumask_test_cpu(cpu, to_cpumask(tick_broadcast_oneshot_mask))) {
 396                struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
 397
 398                clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_ONESHOT);
 399        }
 400}
 401
 402/*
 403 * Handle oneshot mode broadcasting
 404 */
 405static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 406{
 407        struct tick_device *td;
 408        ktime_t now, next_event;
 409        int cpu;
 410
 411        raw_spin_lock(&tick_broadcast_lock);
 412again:
 413        dev->next_event.tv64 = KTIME_MAX;
 414        next_event.tv64 = KTIME_MAX;
 415        cpumask_clear(to_cpumask(tmpmask));
 416        now = ktime_get();
 417        /* Find all expired events */
 418        for_each_cpu(cpu, tick_get_broadcast_oneshot_mask()) {
 419                td = &per_cpu(tick_cpu_device, cpu);
 420                if (td->evtdev->next_event.tv64 <= now.tv64)
 421                        cpumask_set_cpu(cpu, to_cpumask(tmpmask));
 422                else if (td->evtdev->next_event.tv64 < next_event.tv64)
 423                        next_event.tv64 = td->evtdev->next_event.tv64;
 424        }
 425
 426        /*
 427         * Wakeup the cpus which have an expired event.
 428         */
 429        tick_do_broadcast(to_cpumask(tmpmask));
 430
 431        /*
 432         * Two reasons for reprogram:
 433         *
 434         * - The global event did not expire any CPU local
 435         * events. This happens in dyntick mode, as the maximum PIT
 436         * delta is quite small.
 437         *
 438         * - There are pending events on sleeping CPUs which were not
 439         * in the event mask
 440         */
 441        if (next_event.tv64 != KTIME_MAX) {
 442                /*
 443                 * Rearm the broadcast device. If event expired,
 444                 * repeat the above
 445                 */
 446                if (tick_broadcast_set_event(next_event, 0))
 447                        goto again;
 448        }
 449        raw_spin_unlock(&tick_broadcast_lock);
 450}
 451
 452/*
 453 * Powerstate information: The system enters/leaves a state, where
 454 * affected devices might stop
 455 */
 456void tick_broadcast_oneshot_control(unsigned long reason)
 457{
 458        struct clock_event_device *bc, *dev;
 459        struct tick_device *td;
 460        unsigned long flags;
 461        int cpu;
 462
 463        /*
 464         * Periodic mode does not care about the enter/exit of power
 465         * states
 466         */
 467        if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 468                return;
 469
 470        /*
 471         * We are called with preemtion disabled from the depth of the
 472         * idle code, so we can't be moved away.
 473         */
 474        cpu = smp_processor_id();
 475        td = &per_cpu(tick_cpu_device, cpu);
 476        dev = td->evtdev;
 477
 478        if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 479                return;
 480
 481        bc = tick_broadcast_device.evtdev;
 482
 483        raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 484        if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
 485                if (!cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
 486                        cpumask_set_cpu(cpu, tick_get_broadcast_oneshot_mask());
 487                        clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
 488                        if (dev->next_event.tv64 < bc->next_event.tv64)
 489                                tick_broadcast_set_event(dev->next_event, 1);
 490                }
 491        } else {
 492                if (cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
 493                        cpumask_clear_cpu(cpu,
 494                                          tick_get_broadcast_oneshot_mask());
 495                        clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 496                        if (dev->next_event.tv64 != KTIME_MAX)
 497                                tick_program_event(dev->next_event, 1);
 498                }
 499        }
 500        raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 501}
 502
 503/*
 504 * Reset the one shot broadcast for a cpu
 505 *
 506 * Called with tick_broadcast_lock held
 507 */
 508static void tick_broadcast_clear_oneshot(int cpu)
 509{
 510        cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());
 511}
 512
 513static void tick_broadcast_init_next_event(struct cpumask *mask,
 514                                           ktime_t expires)
 515{
 516        struct tick_device *td;
 517        int cpu;
 518
 519        for_each_cpu(cpu, mask) {
 520                td = &per_cpu(tick_cpu_device, cpu);
 521                if (td->evtdev)
 522                        td->evtdev->next_event = expires;
 523        }
 524}
 525
 526/**
 527 * tick_broadcast_setup_oneshot - setup the broadcast device
 528 */
 529void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 530{
 531        int cpu = smp_processor_id();
 532
 533        /* Set it up only once ! */
 534        if (bc->event_handler != tick_handle_oneshot_broadcast) {
 535                int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;
 536
 537                bc->event_handler = tick_handle_oneshot_broadcast;
 538
 539                /* Take the do_timer update */
 540                tick_do_timer_cpu = cpu;
 541
 542                /*
 543                 * We must be careful here. There might be other CPUs
 544                 * waiting for periodic broadcast. We need to set the
 545                 * oneshot_mask bits for those and program the
 546                 * broadcast device to fire.
 547                 */
 548                cpumask_copy(to_cpumask(tmpmask), tick_get_broadcast_mask());
 549                cpumask_clear_cpu(cpu, to_cpumask(tmpmask));
 550                cpumask_or(tick_get_broadcast_oneshot_mask(),
 551                           tick_get_broadcast_oneshot_mask(),
 552                           to_cpumask(tmpmask));
 553
 554                if (was_periodic && !cpumask_empty(to_cpumask(tmpmask))) {
 555                        clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 556                        tick_broadcast_init_next_event(to_cpumask(tmpmask),
 557                                                       tick_next_period);
 558                        tick_broadcast_set_event(tick_next_period, 1);
 559                } else
 560                        bc->next_event.tv64 = KTIME_MAX;
 561        } else {
 562                /*
 563                 * The first cpu which switches to oneshot mode sets
 564                 * the bit for all other cpus which are in the general
 565                 * (periodic) broadcast mask. So the bit is set and
 566                 * would prevent the first broadcast enter after this
 567                 * to program the bc device.
 568                 */
 569                tick_broadcast_clear_oneshot(cpu);
 570        }
 571}
 572
 573/*
 574 * Select oneshot operating mode for the broadcast device
 575 */
 576void tick_broadcast_switch_to_oneshot(void)
 577{
 578        struct clock_event_device *bc;
 579        unsigned long flags;
 580
 581        raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 582
 583        tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 584        bc = tick_broadcast_device.evtdev;
 585        if (bc)
 586                tick_broadcast_setup_oneshot(bc);
 587
 588        raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 589}
 590
 591
 592/*
 593 * Remove a dead CPU from broadcasting
 594 */
 595void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
 596{
 597        unsigned long flags;
 598        unsigned int cpu = *cpup;
 599
 600        raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 601
 602        /*
 603         * Clear the broadcast mask flag for the dead cpu, but do not
 604         * stop the broadcast device!
 605         */
 606        cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());
 607
 608        raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 609}
 610
 611/*
 612 * Check, whether the broadcast device is in one shot mode
 613 */
 614int tick_broadcast_oneshot_active(void)
 615{
 616        return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
 617}
 618
 619/*
 620 * Check whether the broadcast device supports oneshot.
 621 */
 622bool tick_broadcast_oneshot_available(void)
 623{
 624        struct clock_event_device *bc = tick_broadcast_device.evtdev;
 625
 626        return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
 627}
 628
 629#endif
 630
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