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 (bc->mode == 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                     cpu_isset(cpu, tick_broadcast_mask)) {
 247                         cpu_clear(cpu, tick_broadcast_mask);
 248                         if (bc->mode == TICKDEV_MODE_PERIODIC)
 249                                 tick_setup_periodic(dev, 0);
 250                 }
 251                 break;
 252         }
 253
 254         if (cpus_empty(tick_broadcast_mask)) {
 255                 if (!bc_stopped)
 256                         clockevents_shutdown(bc);
 257         } else if (bc_stopped) {
 258                 if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 259                         tick_broadcast_start_periodic(bc);
 260                 else
 261                         tick_broadcast_setup_oneshot(bc);
 262         }
 263 out:
 264         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 265 }
 266
 267 /*
 268  * Powerstate information: The system enters/leaves a state, where
 269  * affected devices might stop.
 270  */
 271 void tick_broadcast_on_off(unsigned long reason, int *oncpu)
 272 {
 273         if (!cpu_isset(*oncpu, cpu_online_map))
 274                 printk(KERN_ERR "tick-broadcast: ignoring broadcast for "
 275                        "offline CPU #%d\n", *oncpu);
 276         else
 277                 smp_call_function_single(*oncpu, tick_do_broadcast_on_off,
 278                                          &reason, 1);
 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         spin_lock_irqsave(&tick_broadcast_lock, flags);
 302
 303         bc = tick_broadcast_device.evtdev;
 304         cpu_clear(cpu, tick_broadcast_mask);
 305
 306         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC) {
 307                 if (bc && cpus_empty(tick_broadcast_mask))
 308                         clockevents_shutdown(bc);
 309         }
 310
 311         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         spin_lock_irqsave(&tick_broadcast_lock, flags);
 320
 321         bc = tick_broadcast_device.evtdev;
 322         if (bc)
 323                 clockevents_shutdown(bc);
 324
 325         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         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(!cpus_empty(tick_broadcast_mask))
 344                                 tick_broadcast_start_periodic(bc);
 345                         broadcast = cpu_isset(smp_processor_id(),
 346                                               tick_broadcast_mask);
 347                         break;
 348                 case TICKDEV_MODE_ONESHOT:
 349                         broadcast = tick_resume_broadcast_oneshot(bc);
 350                         break;
 351                 }
 352         }
 353         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 354
 355         return broadcast;
 356 }
 357
 358
 359 #ifdef CONFIG_TICK_ONESHOT
 360
 361 static cpumask_t tick_broadcast_oneshot_mask;
 362
 363 /*
 364  * Debugging: see timer_list.c
 365  */
 366 cpumask_t *tick_get_broadcast_oneshot_mask(void)
 367 {
 368         return &tick_broadcast_oneshot_mask;
 369 }
 370
 371 static int tick_broadcast_set_event(ktime_t expires, int force)
 372 {
 373         struct clock_event_device *bc = tick_broadcast_device.evtdev;
 374
 375         return tick_dev_program_event(bc, expires, force);
 376 }
 377
 378 int tick_resume_broadcast_oneshot(struct clock_event_device *bc)
 379 {
 380         clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 381         return 0;
 382 }
 383
 384 /*
 385  * Handle oneshot mode broadcasting
 386  */
 387 static void tick_handle_oneshot_broadcast(struct clock_event_device *dev)
 388 {
 389         struct tick_device *td;
 390         cpumask_t mask;
 391         ktime_t now, next_event;
 392         int cpu;
 393
 394         spin_lock(&tick_broadcast_lock);
 395 again:
 396         dev->next_event.tv64 = KTIME_MAX;
 397         next_event.tv64 = KTIME_MAX;
 398         mask = CPU_MASK_NONE;
 399         now = ktime_get();
 400         /* Find all expired events */
 401         for_each_cpu_mask_nr(cpu, tick_broadcast_oneshot_mask) {
 402                 td = &per_cpu(tick_cpu_device, cpu);
 403                 if (td->evtdev->next_event.tv64 <= now.tv64)
 404                         cpu_set(cpu, mask);
 405                 else if (td->evtdev->next_event.tv64 < next_event.tv64)
 406                         next_event.tv64 = td->evtdev->next_event.tv64;
 407         }
 408
 409         /*
 410          * Wakeup the cpus which have an expired event.
 411          */
 412         tick_do_broadcast(mask);
 413
 414         /*
 415          * Two reasons for reprogram:
 416          *
 417          * - The global event did not expire any CPU local
 418          * events. This happens in dyntick mode, as the maximum PIT
 419          * delta is quite small.
 420          *
 421          * - There are pending events on sleeping CPUs which were not
 422          * in the event mask
 423          */
 424         if (next_event.tv64 != KTIME_MAX) {
 425                 /*
 426                  * Rearm the broadcast device. If event expired,
 427                  * repeat the above
 428                  */
 429                 if (tick_broadcast_set_event(next_event, 0))
 430                         goto again;
 431         }
 432         spin_unlock(&tick_broadcast_lock);
 433 }
 434
 435 /*
 436  * Powerstate information: The system enters/leaves a state, where
 437  * affected devices might stop
 438  */
 439 void tick_broadcast_oneshot_control(unsigned long reason)
 440 {
 441         struct clock_event_device *bc, *dev;
 442         struct tick_device *td;
 443         unsigned long flags;
 444         int cpu;
 445
 446         spin_lock_irqsave(&tick_broadcast_lock, flags);
 447
 448         /*
 449          * Periodic mode does not care about the enter/exit of power
 450          * states
 451          */
 452         if (tick_broadcast_device.mode == TICKDEV_MODE_PERIODIC)
 453                 goto out;
 454
 455         bc = tick_broadcast_device.evtdev;
 456         cpu = smp_processor_id();
 457         td = &per_cpu(tick_cpu_device, cpu);
 458         dev = td->evtdev;
 459
 460         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
 461                 goto out;
 462
 463         if (reason == CLOCK_EVT_NOTIFY_BROADCAST_ENTER) {
 464                 if (!cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 465                         cpu_set(cpu, tick_broadcast_oneshot_mask);
 466                         clockevents_set_mode(dev, CLOCK_EVT_MODE_SHUTDOWN);
 467                         if (dev->next_event.tv64 < bc->next_event.tv64)
 468                                 tick_broadcast_set_event(dev->next_event, 1);
 469                 }
 470         } else {
 471                 if (cpu_isset(cpu, tick_broadcast_oneshot_mask)) {
 472                         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 473                         clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 474                         if (dev->next_event.tv64 != KTIME_MAX)
 475                                 tick_program_event(dev->next_event, 1);
 476                 }
 477         }
 478
 479 out:
 480         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 481 }
 482
 483 /*
 484  * Reset the one shot broadcast for a cpu
 485  *
 486  * Called with tick_broadcast_lock held
 487  */
 488 static void tick_broadcast_clear_oneshot(int cpu)
 489 {
 490         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 491 }
 492
 493 static void tick_broadcast_init_next_event(cpumask_t *mask, ktime_t expires)
 494 {
 495         struct tick_device *td;
 496         int cpu;
 497
 498         for_each_cpu_mask_nr(cpu, *mask) {
 499                 td = &per_cpu(tick_cpu_device, cpu);
 500                 if (td->evtdev)
 501                         td->evtdev->next_event = expires;
 502         }
 503 }
 504
 505 /**
 506  * tick_broadcast_setup_oneshot - setup the broadcast device
 507  */
 508 void tick_broadcast_setup_oneshot(struct clock_event_device *bc)
 509 {
 510         /* Set it up only once ! */
 511         if (bc->event_handler != tick_handle_oneshot_broadcast) {
 512                 int was_periodic = bc->mode == CLOCK_EVT_MODE_PERIODIC;
 513                 int cpu = smp_processor_id();
 514                 cpumask_t mask;
 515
 516                 bc->event_handler = tick_handle_oneshot_broadcast;
 517                 clockevents_set_mode(bc, CLOCK_EVT_MODE_ONESHOT);
 518
 519                 /* Take the do_timer update */
 520                 tick_do_timer_cpu = cpu;
 521
 522                 /*
 523                  * We must be careful here. There might be other CPUs
 524                  * waiting for periodic broadcast. We need to set the
 525                  * oneshot_mask bits for those and program the
 526                  * broadcast device to fire.
 527                  */
 528                 mask = tick_broadcast_mask;
 529                 cpu_clear(cpu, mask);
 530                 cpus_or(tick_broadcast_oneshot_mask,
 531                         tick_broadcast_oneshot_mask, mask);
 532
 533                 if (was_periodic && !cpus_empty(mask)) {
 534                         tick_broadcast_init_next_event(&mask, tick_next_period);
 535                         tick_broadcast_set_event(tick_next_period, 1);
 536                 } else
 537                         bc->next_event.tv64 = KTIME_MAX;
 538         }
 539 }
 540
 541 /*
 542  * Select oneshot operating mode for the broadcast device
 543  */
 544 void tick_broadcast_switch_to_oneshot(void)
 545 {
 546         struct clock_event_device *bc;
 547         unsigned long flags;
 548
 549         spin_lock_irqsave(&tick_broadcast_lock, flags);
 550
 551         tick_broadcast_device.mode = TICKDEV_MODE_ONESHOT;
 552         bc = tick_broadcast_device.evtdev;
 553         if (bc)
 554                 tick_broadcast_setup_oneshot(bc);
 555         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 556 }
 557
 558
 559 /*
 560  * Remove a dead CPU from broadcasting
 561  */
 562 void tick_shutdown_broadcast_oneshot(unsigned int *cpup)
 563 {
 564         unsigned long flags;
 565         unsigned int cpu = *cpup;
 566
 567         spin_lock_irqsave(&tick_broadcast_lock, flags);
 568
 569         /*
 570          * Clear the broadcast mask flag for the dead cpu, but do not
 571          * stop the broadcast device!
 572          */
 573         cpu_clear(cpu, tick_broadcast_oneshot_mask);
 574
 575         spin_unlock_irqrestore(&tick_broadcast_lock, flags);
 576 }
 577
 578 /*
 579  * Check, whether the broadcast device is in one shot mode
 580  */
 581 int tick_broadcast_oneshot_active(void)
 582 {
 583         return tick_broadcast_device.mode == TICKDEV_MODE_ONESHOT;
 584 }
 585
 586 #endif