kernel/time/tick-broadcast.c

   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 #include <linux/smp.h>
  22
  23 #include "tick-internal.h"
  24
  25 /*
  26  * Broadcast support for broken x86 hardware, where the local apic
  27  * timer stops in C3 state.
  28  */
  29
  30 static struct tick_device tick_broadcast_device;
  31 /* FIXME: Use cpumask_var_t. */
  32 static DECLARE_BITMAP(tick_broadcast_mask, NR_CPUS);
  33 static DECLARE_BITMAP(tmpmask, NR_CPUS);
  34 static DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
  35 static int tick_broadcast_force;
  36
  37 #ifdef CONFIG_TICK_ONESHOT
  38 static void tick_broadcast_clear_oneshot(int cpu);
  39 #else
  40 static inline void tick_broadcast_clear_oneshot(int cpu) { }
  41 #endif
  42
  43 /*
  44  * Debugging: see timer_list.c
  45  */
  46 struct tick_device *tick_get_broadcast_device(void)
  47 {
  48         return &tick_broadcast_device;
  49 }
  50
  51 struct cpumask *tick_get_broadcast_mask(void)
  52 {
  53         return to_cpumask(tick_broadcast_mask);
  54 }
  55
  56 /*
  57  * Start the device in periodic mode
  58  */
  59 static void tick_broadcast_start_periodic(struct clock_event_device *bc)
  60 {
  61         if (bc)
  62                 tick_setup_periodic(bc, 1);
  63 }
  64
  65 /*
  66  * Check, if the device can be utilized as broadcast device:
  67  */
  68 int tick_check_broadcast_device(struct clock_event_device *dev)
  69 {
  70         if ((dev->features & CLOCK_EVT_FEAT_DUMMY) ||
  71             (tick_broadcast_device.evtdev &&
  72              tick_broadcast_device.evtdev->rating >= dev->rating) ||
  73              (dev->features & CLOCK_EVT_FEAT_C3STOP))
  74                 return 0;
  75
  76         clockevents_exchange_device(tick_broadcast_device.evtdev, dev);
  77         tick_broadcast_device.evtdev = dev;
  78         if (!cpumask_empty(tick_get_broadcast_mask()))
  79                 tick_broadcast_start_periodic(dev);
  80         return 1;
  81 }
  82
  83 /*
  84  * Check, if the device is the broadcast device
  85  */
  86 int tick_is_broadcast_device(struct clock_event_device *dev)
  87 {
  88         return (dev && tick_broadcast_device.evtdev == dev);
  89 }
  90
  91 static void err_broadcast(const struct cpumask *mask)
  92 {
  93         pr_crit_once("Failed to broadcast timer tick. Some CPUs may be unresponsive.\n");
  94 }
  95
  96 static void tick_device_setup_broadcast_func(struct clock_event_device *dev)
  97 {
  98         if (!dev->broadcast)
  99                 dev->broadcast = tick_broadcast;
 100         if (!dev->broadcast) {
 101                 pr_warn_once("%s depends on broadcast, but no broadcast function available\n",
 102                              dev->name);
 103                 dev->broadcast = err_broadcast;
 104         }
 105 }
 106
 107 /*
 108  * Check, if the device is disfunctional and a place holder, which
 109  * needs to be handled by the broadcast device.
 110  */
 111 int tick_device_uses_broadcast(struct clock_event_device *dev, int cpu)
 112 {
 113         unsigned long flags;
 114         int ret = 0;
 115
 116         raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 117
 118         /*
 119          * Devices might be registered with both periodic and oneshot
 120          * mode disabled. This signals, that the device needs to be
 121          * operated from the broadcast device and is a placeholder for
 122          * the cpu local device.
 123          */
 124         if (!tick_device_is_functional(dev)) {
 125                 dev->event_handler = tick_handle_periodic;
 126                 tick_device_setup_broadcast_func(dev);
 127                 cpumask_set_cpu(cpu, tick_get_broadcast_mask());
 128                 tick_broadcast_start_periodic(tick_broadcast_device.evtdev);
 129                 ret = 1;
 130         } else {
 131                 /*
 132                  * When the new device is not affected by the stop
 133                  * feature and the cpu is marked in the broadcast mask
 134                  * then clear the broadcast bit.
 135                  */
 136                 if (!(dev->features & CLOCK_EVT_FEAT_C3STOP)) {
 137                         int cpu = smp_processor_id();
 138                         cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
 139                         tick_broadcast_clear_oneshot(cpu);
 140                 } else {
 141                         tick_device_setup_broadcast_func(dev);
 142                 }
 143         }
 144         raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 145         return ret;
 146 }
 147
 148 #ifdef CONFIG_GENERIC_CLOCKEVENTS_BROADCAST
 149 int tick_receive_broadcast(void)
 150 {
 151         struct tick_device *td = this_cpu_ptr(&tick_cpu_device);
 152         struct clock_event_device *evt = td->evtdev;
 153
 154         if (!evt)
 155                 return -ENODEV;
 156
 157         if (!evt->event_handler)
 158                 return -EINVAL;
 159
 160         evt->event_handler(evt);
 161         return 0;
 162 }
 163 #endif
 164
 165 /*
 166  * Broadcast the event to the cpus, which are set in the mask (mangled).
 167  */
 168 static void tick_do_broadcast(struct cpumask *mask)
 169 {
 170         int cpu = smp_processor_id();
 171         struct tick_device *td;
 172
 173         /*
 174          * Check, if the current cpu is in the mask
 175          */
 176         if (cpumask_test_cpu(cpu, mask)) {
 177                 cpumask_clear_cpu(cpu, mask);
 178                 td = &per_cpu(tick_cpu_device, cpu);
 179                 td->evtdev->event_handler(td->evtdev);
 180         }
 181
 182         if (!cpumask_empty(mask)) {
 183                 /*
 184                  * It might be necessary to actually check whether the devices
 185                  * have different broadcast functions. For now, just use the
 186                  * one of the first device. This works as long as we have this
 187                  * misfeature only on x86 (lapic)
 188                  */
 189                 td = &per_cpu(tick_cpu_device, cpumask_first(mask));
 190                 td->evtdev->broadcast(mask);
 191         }
 192 }
 193
 194 /*
 195  * Periodic broadcast:
 196  * - invoke the broadcast handlers
 197  */
 198 static void tick_do_periodic_broadcast(void)
 199 {
 200         raw_spin_lock(&tick_broadcast_lock);
 201
 202         cpumask_and(to_cpumask(tmpmask),
 203                     cpu_online_mask, tick_get_broadcast_mask());
 204         tick_do_broadcast(to_cpumask(tmpmask));
 205
 206         raw_spin_unlock(&tick_broadcast_lock);
 207 }
 208
 209 /*
 210  * Event handler for periodic broadcast ticks
 211  */
 212 static void tick_handle_periodic_broadcast(struct clock_event_device *dev)
 213 {
 214         ktime_t next;
 215
 216         tick_do_periodic_broadcast();
 217
 218         /*
 219          * The device is in periodic mode. No reprogramming necessary:
 220          */
 221         if (dev->mode == CLOCK_EVT_MODE_PERIODIC)
 222                 return;
 223
 224         /*
 225          * Setup the next period for devices, which do not have
 226          * periodic mode. We read dev->next_event first and add to it
 227          * when the event already expired. clockevents_program_event()
 228          * sets dev->next_event only when the event is really
 229          * programmed to the device.
 230          */
 231         for (next = dev->next_event; ;) {
 232                 next = ktime_add(next, tick_period);
 233
 234                 if (!clockevents_program_event(dev, next, false))
 235                         return;
 236                 tick_do_periodic_broadcast();
 237         }
 238 }
 239
 240 /*
 241  * Powerstate information: The system enters/leaves a state, where
 242  * affected devices might stop
 243  */
 244 static void tick_do_broadcast_on_off(unsigned long *reason)
 245 {
 246         struct clock_event_device *bc, *dev;
 247         struct tick_device *td;
 248         unsigned long flags;
 249         int cpu, bc_stopped;
 250
 251         raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 252
 253         cpu = smp_processor_id();
 254         td = &per_cpu(tick_cpu_device, cpu);
 255         dev = td->evtdev;
 256         bc = tick_broadcast_device.evtdev;
 257
 258         /*
 259          * Is the device not affected by the powerstate ?
 260          */
 261         if (!dev || !(dev->features & CLOCK_EVT_FEAT_C3STOP))
 262                 goto out;
 263
 264         if (!tick_device_is_functional(dev))
 265                 goto out;
 266
 267         bc_stopped = cpumask_empty(tick_get_broadcast_mask());
 268
 269         switch (*reason) {
 270         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 271         case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 272                 if (!cpumask_test_cpu(cpu, tick_get_broadcast_mask())) {
 273                         cpumask_set_cpu(cpu, tick_get_broadcast_mask());
 274                         if (tick_broadcast_device.mode ==
 275                             TICKDEV_MODE_PERIODIC)
 276                                 clockevents_shutdown(dev);
 277                 }
 278                 if (*reason == CLOCK_EVT_NOTIFY_BROADCAST_FORCE)
 279                         tick_broadcast_force = 1;
 280                 break;
 281         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 282                 if (!tick_broadcast_force &&
 283                     cpumask_test_cpu(cpu, tick_get_broadcast_mask())) {
 284                         cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
 285                         if (tick_broadcast_device.mode ==
 286                             TICKDEV_MODE_PERIODIC)
 287                                 tick_setup_periodic(dev, 0);
 288                 }
 289                 break;
 290         }
 291
 292         if (cpumask_empty(tick_get_broadcast_mask())) {
 293                 if (!bc_stopped)
 294                         clockevents_shutdown(bc);
 295         } else if (bc_stopped) {
 296                 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 297                         tick_broadcast_start_periodic(bc);
 298                 else
 299                         tick_broadcast_setup_oneshot(bc);
 300         }
 301 out:
 302         raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 303 }
 304
 305 /*
 306  * Powerstate information: The system enters/leaves a state, where
 307  * affected devices might stop.
 308  */
 309 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 310 {
 311         if (!cpumask_test_cpu(*oncpu, cpu_online_mask))
 312                 printk(KERN_ERR "tick-broadcast: ignoring broadcast for "
 313                        "offline CPU #%d\n", *oncpu);
 314         else
 315                 tick_do_broadcast_on_off(&reason);
 316 }
 317
 318 /*
 319  * Set the periodic handler depending on broadcast on/off
 320  */
 321 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 322 {
 323         if (!broadcast)
 324                 dev->event_handler = tick_handle_periodic;
 325         else
 326                 dev->event_handler = tick_handle_periodic_broadcast;
 327 }
 328
 329 /*
 330  * Remove a CPU from broadcasting
 331  */
 332 void tick_shutdown_broadcast(unsigned int *cpup)
 333 {
 334         struct clock_event_device *bc;
 335         unsigned long flags;
 336         unsigned int cpu = *cpup;
 337
 338         raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 339
 340         bc = tick_broadcast_device.evtdev;
 341         cpumask_clear_cpu(cpu, tick_get_broadcast_mask());
 342
 343         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 344                 if (bc && cpumask_empty(tick_get_broadcast_mask()))
 345                         clockevents_shutdown(bc);
 346         }
 347
 348         raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 349 }
 350
 351 void tick_suspend_broadcast(void)
 352 {
 353         struct clock_event_device *bc;
 354         unsigned long flags;
 355
 356         raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 357
 358         bc = tick_broadcast_device.evtdev;
 359         if (bc)
 360                 clockevents_shutdown(bc);
 361
 362         raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 363 }
 364
 365 int tick_resume_broadcast(void)
 366 {
 367         struct clock_event_device *bc;
 368         unsigned long flags;
 369         int broadcast = 0;
 370
 371         raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 372
 373         bc = tick_broadcast_device.evtdev;
 374
 375         if (bc) {
 376                 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
 377
 378                 switch (tick_broadcast_device.mode) {
 379                 case TICKDEV_MODE_PERIODIC:
 380                         if (!cpumask_empty(tick_get_broadcast_mask()))
 381                                 tick_broadcast_start_periodic(bc);
 382                         broadcast = cpumask_test_cpu(smp_processor_id(),
 383                                                      tick_get_broadcast_mask());
 384                         break;
 385                 case TICKDEV_MODE_ONESHOT:
 386                         if (!cpumask_empty(tick_get_broadcast_mask()))
 387                                 broadcast = tick_resume_broadcast_oneshot(bc);
 388                         break;
 389                 }
 390         }
 391         raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 392
 393         return broadcast;
 394 }
 395
 396
 397 #ifdef CONFIG_TICK_ONESHOT
 398
 399 /* FIXME: use cpumask_var_t. */
 400 static DECLARE_BITMAP(tick_broadcast_oneshot_mask, NR_CPUS);
 401
 402 /*
 403  * Exposed for debugging: see timer_list.c
 404  */
 405 struct cpumask *tick_get_broadcast_oneshot_mask(void)
 406 {
 407         return to_cpumask(tick_broadcast_oneshot_mask);
 408 }
 409
 410 static int tick_broadcast_set_event(ktime_t expires, int force)
 411 {
 412         struct clock_event_device *bc = tick_broadcast_device.evtdev;
 413
 414         if (bc->mode != CLOCK_EVT_MODE_ONESHOT)
 415                 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 416
 417         return clockevents_program_event(bc, expires, force);
 418 }
 419
 420 int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 421 {
 422         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 423         return 0;
 424 }
 425
 426 /*
 427  * Called from irq_enter() when idle was interrupted to reenable the
 428  * per cpu device.
 429  */
 430 void tick_check_oneshot_broadcast(int cpu)
 431 {
 432         if (cpumask_test_cpu(cpu, to_cpumask(tick_broadcast_oneshot_mask))) {
 433                 struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
 434
 435                 clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_ONESHOT);
 436         }
 437 }
 438
 439 /*
 440  * Handle oneshot mode broadcasting
 441  */
 442 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 443 {
 444         struct tick_device *td;
 445         ktime_t now, next_event;
 446         int cpu;
 447
 448         raw_spin_lock(&tick_broadcast_lock);
 449 again:
 450         dev->next_event.tv64 = KTIME_MAX;
 451         next_event.tv64 = KTIME_MAX;
 452         cpumask_clear(to_cpumask(tmpmask));
 453         now = ktime_get();
 454         /* Find all expired events */
 455         for_each_cpu(cpu, tick_get_broadcast_oneshot_mask()) {
 456                 td = &per_cpu(tick_cpu_device, cpu);
 457                 if (td->evtdev->next_event.tv64 <= now.tv64)
 458                         cpumask_set_cpu(cpu, to_cpumask(tmpmask));
 459                 else if (td->evtdev->next_event.tv64 < next_event.tv64)
 460                         next_event.tv64 = td->evtdev->next_event.tv64;
 461         }
 462
 463         /*
 464          * Wakeup the cpus which have an expired event.
 465          */
 466         tick_do_broadcast(to_cpumask(tmpmask));
 467
 468         /*
 469          * Two reasons for reprogram:
 470          *
 471          * - The global event did not expire any CPU local
 472          * events. This happens in dyntick mode, as the maximum PIT
 473          * delta is quite small.
 474          *
 475          * - There are pending events on sleeping CPUs which were not
 476          * in the event mask
 477          */
 478         if (next_event.tv64 != KTIME_MAX) {
 479                 /*
 480                  * Rearm the broadcast device. If event expired,
 481                  * repeat the above
 482                  */
 483                 if (tick_broadcast_set_event(next_event, 0))
 484                         goto again;
 485         }
 486         raw_spin_unlock(&tick_broadcast_lock);
 487 }
 488
 489 /*
 490  * Powerstate information: The system enters/leaves a state, where
 491  * affected devices might stop
 492  */
 493 void tick_broadcast_oneshot_control(unsigned long reason)
 494 {
 495         struct clock_event_device *bc, *dev;
 496         struct tick_device *td;
 497         unsigned long flags;
 498         int cpu;
 499
 500         /*
 501          * Periodic mode does not care about the enter/exit of power
 502          * states
 503          */
 504         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 505                 return;
 506
 507         /*
 508          * We are called with preemtion disabled from the depth of the
 509          * idle code, so we can't be moved away.
 510          */
 511         cpu = smp_processor_id();
 512         td = &per_cpu(tick_cpu_device, cpu);
 513         dev = td->evtdev;
 514
 515         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 516                 return;
 517
 518         bc = tick_broadcast_device.evtdev;
 519
 520         raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 521         if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
 522                 if (!cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
 523                         cpumask_set_cpu(cpu, tick_get_broadcast_oneshot_mask());
 524                         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
 525                         if (dev->next_event.tv64 < bc->next_event.tv64)
 526                                 tick_broadcast_set_event(dev->next_event, 1);
 527                 }
 528         } else {
 529                 if (cpumask_test_cpu(cpu, tick_get_broadcast_oneshot_mask())) {
 530                         cpumask_clear_cpu(cpu,
 531                                           tick_get_broadcast_oneshot_mask());
 532                         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 533                         if (dev->next_event.tv64 != KTIME_MAX)
 534                                 tick_program_event(dev->next_event, 1);
 535                 }
 536         }
 537         raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 538 }
 539
 540 /*
 541  * Reset the one shot broadcast for a cpu
 542  *
 543  * Called with tick_broadcast_lock held
 544  */
 545 static void tick_broadcast_clear_oneshot(int cpu)
 546 {
 547         cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());
 548 }
 549
 550 static void tick_broadcast_init_next_event(struct cpumask *mask,
 551                                            ktime_t expires)
 552 {
 553         struct tick_device *td;
 554         int cpu;
 555
 556         for_each_cpu(cpu, mask) {
 557                 td = &per_cpu(tick_cpu_device, cpu);
 558                 if (td->evtdev)
 559                         td->evtdev->next_event = expires;
 560         }
 561 }
 562
 563 /**
 564  * tick_broadcast_setup_oneshot - setup the broadcast device
 565  */
 566 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 567 {
 568         int cpu = smp_processor_id();
 569
 570         /* Set it up only once ! */
 571         if (bc->event_handler != tick_handle_oneshot_broadcast) {
 572                 int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;
 573
 574                 bc->event_handler = tick_handle_oneshot_broadcast;
 575
 576                 /* Take the do_timer update */
 577                 tick_do_timer_cpu = cpu;
 578
 579                 /*
 580                  * We must be careful here. There might be other CPUs
 581                  * waiting for periodic broadcast. We need to set the
 582                  * oneshot_mask bits for those and program the
 583                  * broadcast device to fire.
 584                  */
 585                 cpumask_copy(to_cpumask(tmpmask), tick_get_broadcast_mask());
 586                 cpumask_clear_cpu(cpu, to_cpumask(tmpmask));
 587                 cpumask_or(tick_get_broadcast_oneshot_mask(),
 588                            tick_get_broadcast_oneshot_mask(),
 589                            to_cpumask(tmpmask));
 590
 591                 if (was_periodic && !cpumask_empty(to_cpumask(tmpmask))) {
 592                         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 593                         tick_broadcast_init_next_event(to_cpumask(tmpmask),
 594                                                        tick_next_period);
 595                         tick_broadcast_set_event(tick_next_period, 1);
 596                 } else
 597                         bc->next_event.tv64 = KTIME_MAX;
 598         } else {
 599                 /*
 600                  * The first cpu which switches to oneshot mode sets
 601                  * the bit for all other cpus which are in the general
 602                  * (periodic) broadcast mask. So the bit is set and
 603                  * would prevent the first broadcast enter after this
 604                  * to program the bc device.
 605                  */
 606                 tick_broadcast_clear_oneshot(cpu);
 607         }
 608 }
 609
 610 /*
 611  * Select oneshot operating mode for the broadcast device
 612  */
 613 void tick_broadcast_switch_to_oneshot(void)
 614 {
 615         struct clock_event_device *bc;
 616         unsigned long flags;
 617
 618         raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 619
 620         tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 621         bc = tick_broadcast_device.evtdev;
 622         if (bc)
 623                 tick_broadcast_setup_oneshot(bc);
 624
 625         raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 626 }
 627
 628
 629 /*
 630  * Remove a dead CPU from broadcasting
 631  */
 632 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
 633 {
 634         unsigned long flags;
 635         unsigned int cpu = *cpup;
 636
 637         raw_spin_lock_irqsave(&tick_broadcast_lock, flags);
 638
 639         /*
 640          * Clear the broadcast mask flag for the dead cpu, but do not
 641          * stop the broadcast device!
 642          */
 643         cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());
 644
 645         raw_spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 646 }
 647
 648 /*
 649  * Check, whether the broadcast device is in one shot mode
 650  */
 651 int tick_broadcast_oneshot_active(void)
 652 {
 653         return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
 654 }
 655
 656 /*
 657  * Check whether the broadcast device supports oneshot.
 658  */
 659 bool tick_broadcast_oneshot_available(void)
 660 {
 661         struct clock_event_device *bc = tick_broadcast_device.evtdev;
 662
 663         return bc ? bc->features & CLOCK_EVT_FEAT_ONESHOT : false;
 664 }
 665
 666 #endif