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