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
  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
  29 static struct tick_device tick_broadcast_device;
  30 /* FIXME: Use cpumask_var_t. */
  31 static DECLARE_BITMAP(tick_broadcast_mask, NR_CPUS);
  32 static DECLARE_BITMAP(tmpmask, NR_CPUS);
  33 static DEFINE_RAW_SPINLOCK(tick_broadcast_lock);
  34 static int tick_broadcast_force;
  35
  36 #ifdef CONFIG_TICK_ONESHOT
  37 static void tick_broadcast_clear_oneshot(int cpu);
  38 #else
  39 static inline void tick_broadcast_clear_oneshot(int cpu) { }
  40 #endif
  41
  42 /*
  43  * Debugging: see timer_list.c
  44  */
  45 struct tick_device *tick_get_broadcast_device(void)
  46 {
  47         return &tick_broadcast_device;
  48 }
  49
  50 struct 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  */
  58 static 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  */
  67 int 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  */
  84 int 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  */
  93 int 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  */
 131 static 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  */
 161 static 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  */
 175 static 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  */
 207 static 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         }
 264 out:
 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  */
 272 void 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  */
 284 void 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  */
 295 void 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
 314 void 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
 328 int 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. */
 363 static DECLARE_BITMAP(tick_broadcast_oneshot_mask, NR_CPUS);
 364
 365 /*
 366  * Exposed for debugging: see timer_list.c
 367  */
 368 struct cpumask *tick_get_broadcast_oneshot_mask(void)
 369 {
 370         return to_cpumask(tick_broadcast_oneshot_mask);
 371 }
 372
 373 static 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
 383 int 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  */
 393 void 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  */
 405 static 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);
 412 again:
 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  */
 456 void 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  */
 508 static void tick_broadcast_clear_oneshot(int cpu)
 509 {
 510         cpumask_clear_cpu(cpu, tick_get_broadcast_oneshot_mask());
 511 }
 512
 513 static 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  */
 529 void 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  */
 576 void 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  */
 595 void 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  */
 614 int 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  */
 622 bool 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