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(void *why)
 209 {
 210         struct clock_event_device *bc, *dev;
 211         struct tick_device *td;
 212         unsigned long flags, *reason = why;
 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                 smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
 280                                          &reason, 1);
 281 }
 282
 283 /*
 284  * Set the periodic handler depending on broadcast on/off
 285  */
 286 void tick_set_periodic_handler(struct clock_event_device *dev, int broadcast)
 287 {
 288         if (!broadcast)
 289                 dev->event_handler = tick_handle_periodic;
 290         else
 291                 dev->event_handler = tick_handle_periodic_broadcast;
 292 }
 293
 294 /*
 295  * Remove a CPU from broadcasting
 296  */
 297 void tick_shutdown_broadcast(unsigned int *cpup)
 298 {
 299         struct clock_event_device *bc;
 300         unsigned long flags;
 301         unsigned int cpu = *cpup;
 302
 303         spin_lock_irqsave(&tick_broadcast_lock, flags);
 304
 305         bc = tick_broadcast_device.evtdev;
 306         cpu_clear(cpu, tick_broadcast_mask);
 307
 308         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 309                 if (bc && cpus_empty(tick_broadcast_mask))
 310                         clockevents_shutdown(bc);
 311         }
 312
 313         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 314 }
 315
 316 void tick_suspend_broadcast(void)
 317 {
 318         struct clock_event_device *bc;
 319         unsigned long flags;
 320
 321         spin_lock_irqsave(&tick_broadcast_lock, flags);
 322
 323         bc = tick_broadcast_device.evtdev;
 324         if (bc)
 325                 clockevents_shutdown(bc);
 326
 327         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 328 }
 329
 330 int tick_resume_broadcast(void)
 331 {
 332         struct clock_event_device *bc;
 333         unsigned long flags;
 334         int broadcast = 0;
 335
 336         spin_lock_irqsave(&tick_broadcast_lock, flags);
 337
 338         bc = tick_broadcast_device.evtdev;
 339
 340         if (bc) {
 341                 clockevents_set_mode(bc, CLOCK_EVT_MODE_RESUME);
 342
 343                 switch (tick_broadcast_device.mode) {
 344                 case TICKDEV_MODE_PERIODIC:
 345                         if(!cpus_empty(tick_broadcast_mask))
 346                                 tick_broadcast_start_periodic(bc);
 347                         broadcast = cpu_isset(smp_processor_id(),
 348                                               tick_broadcast_mask);
 349                         break;
 350                 case TICKDEV_MODE_ONESHOT:
 351                         broadcast = tick_resume_broadcast_oneshot(bc);
 352                         break;
 353                 }
 354         }
 355         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 356
 357         return broadcast;
 358 }
 359
 360
 361 #ifdef CONFIG_TICK_ONESHOT
 362
 363 static cpumask_t tick_broadcast_oneshot_mask;
 364
 365 /*
 366  * Debugging: see timer_list.c
 367  */
 368 cpumask_t *tick_get_broadcast_oneshot_mask(void)
 369 {
 370         return &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         return tick_dev_program_event(bc, expires, force);
 378 }
 379
 380 int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 381 {
 382         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 383         return 0;
 384 }
 385
 386 /*
 387  * Handle oneshot mode broadcasting
 388  */
 389 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 390 {
 391         struct tick_device *td;
 392         cpumask_t mask;
 393         ktime_t now, next_event;
 394         int cpu;
 395
 396         spin_lock(&tick_broadcast_lock);
 397 again:
 398         dev->next_event.tv64 = KTIME_MAX;
 399         next_event.tv64 = KTIME_MAX;
 400         mask = CPU_MASK_NONE;
 401         now = ktime_get();
 402         /* Find all expired events */
 403         for_each_cpu_mask_nr(cpu, tick_broadcast_oneshot_mask) {
 404                 td = &per_cpu(tick_cpu_device, cpu);
 405                 if (td->evtdev->next_event.tv64 <= now.tv64)
 406                         cpu_set(cpu, mask);
 407                 else if (td->evtdev->next_event.tv64 < next_event.tv64)
 408                         next_event.tv64 = td->evtdev->next_event.tv64;
 409         }
 410
 411         /*
 412          * Wakeup the cpus which have an expired event.
 413          */
 414         tick_do_broadcast(mask);
 415
 416         /*
 417          * Two reasons for reprogram:
 418          *
 419          * - The global event did not expire any CPU local
 420          * events. This happens in dyntick mode, as the maximum PIT
 421          * delta is quite small.
 422          *
 423          * - There are pending events on sleeping CPUs which were not
 424          * in the event mask
 425          */
 426         if (next_event.tv64 != KTIME_MAX) {
 427                 /*
 428                  * Rearm the broadcast device. If event expired,
 429                  * repeat the above
 430                  */
 431                 if (tick_broadcast_set_event(next_event, 0))
 432                         goto again;
 433         }
 434         spin_unlock(&tick_broadcast_lock);
 435 }
 436
 437 /*
 438  * Powerstate information: The system enters/leaves a state, where
 439  * affected devices might stop
 440  */
 441 void tick_broadcast_oneshot_control(unsigned long reason)
 442 {
 443         struct clock_event_device *bc, *dev;
 444         struct tick_device *td;
 445         unsigned long flags;
 446         int cpu;
 447
 448         spin_lock_irqsave(&tick_broadcast_lock, flags);
 449
 450         /*
 451          * Periodic mode does not care about the enter/exit of power
 452          * states
 453          */
 454         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 455                 goto out;
 456
 457         bc = tick_broadcast_device.evtdev;
 458         cpu = smp_processor_id();
 459         td = &per_cpu(tick_cpu_device, cpu);
 460         dev = td->evtdev;
 461
 462         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 463                 goto out;
 464
 465         if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
 466                 if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 467                         cpu_set(cpu, tick_broadcast_oneshot_mask);
 468                         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
 469                         if (dev->next_event.tv64 < bc->next_event.tv64)
 470                                 tick_broadcast_set_event(dev->next_event, 1);
 471                 }
 472         } else {
 473                 if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 474                         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 475                         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 476                         if (dev->next_event.tv64 != KTIME_MAX)
 477                                 tick_program_event(dev->next_event, 1);
 478                 }
 479         }
 480
 481 out:
 482         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 483 }
 484
 485 /*
 486  * Reset the one shot broadcast for a cpu
 487  *
 488  * Called with tick_broadcast_lock held
 489  */
 490 static void tick_broadcast_clear_oneshot(int cpu)
 491 {
 492         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 493 }
 494
 495 static void tick_broadcast_init_next_event(cpumask_t *mask, ktime_t expires)
 496 {
 497         struct tick_device *td;
 498         int cpu;
 499
 500         for_each_cpu_mask_nr(cpu, *mask) {
 501                 td = &per_cpu(tick_cpu_device, cpu);
 502                 if (td->evtdev)
 503                         td->evtdev->next_event = expires;
 504         }
 505 }
 506
 507 /**
 508  * tick_broadcast_setup_oneshot - setup the broadcast device
 509  */
 510 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 511 {
 512         /* Set it up only once ! */
 513         if (bc->event_handler != tick_handle_oneshot_broadcast) {
 514                 int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;
 515                 int cpu = smp_processor_id();
 516                 cpumask_t mask;
 517
 518                 bc->event_handler = tick_handle_oneshot_broadcast;
 519                 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 520
 521                 /* Take the do_timer update */
 522                 tick_do_timer_cpu = cpu;
 523
 524                 /*
 525                  * We must be careful here. There might be other CPUs
 526                  * waiting for periodic broadcast. We need to set the
 527                  * oneshot_mask bits for those and program the
 528                  * broadcast device to fire.
 529                  */
 530                 mask = tick_broadcast_mask;
 531                 cpu_clear(cpu, mask);
 532                 cpus_or(tick_broadcast_oneshot_mask,
 533                         tick_broadcast_oneshot_mask, mask);
 534
 535                 if (was_periodic && !cpus_empty(mask)) {
 536                         tick_broadcast_init_next_event(&mask, tick_next_period);
 537                         tick_broadcast_set_event(tick_next_period, 1);
 538                 } else
 539                         bc->next_event.tv64 = KTIME_MAX;
 540         }
 541 }
 542
 543 /*
 544  * Select oneshot operating mode for the broadcast device
 545  */
 546 void tick_broadcast_switch_to_oneshot(void)
 547 {
 548         struct clock_event_device *bc;
 549         unsigned long flags;
 550
 551         spin_lock_irqsave(&tick_broadcast_lock, flags);
 552
 553         tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 554         bc = tick_broadcast_device.evtdev;
 555         if (bc)
 556                 tick_broadcast_setup_oneshot(bc);
 557         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 558 }
 559
 560
 561 /*
 562  * Remove a dead CPU from broadcasting
 563  */
 564 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
 565 {
 566         unsigned long flags;
 567         unsigned int cpu = *cpup;
 568
 569         spin_lock_irqsave(&tick_broadcast_lock, flags);
 570
 571         /*
 572          * Clear the broadcast mask flag for the dead cpu, but do not
 573          * stop the broadcast device!
 574          */
 575         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 576
 577         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 578 }
 579
 580 /*
 581  * Check, whether the broadcast device is in one shot mode
 582  */
 583 int tick_broadcast_oneshot_active(void)
 584 {
 585         return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
 586 }
 587
 588 #endif