kernel/time/tick-common.c

   1 /*
   2  * linux/kernel/time/tick-common.c
   3  *
   4  * This file contains the base functions to manage periodic tick
   5  * related events.
   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 <asm/irq_regs.h>
  24
  25 #include "tick-internal.h"
  26
  27 /*
  28  * Tick devices
  29  */
  30 DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
  31 /*
  32  * Tick next event: keeps track of the tick time
  33  */
  34 ktime_t tick_next_period;
  35 ktime_t tick_period;
  36 int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
  37 DEFINE_SPINLOCK(tick_device_lock);
  38
  39 /*
  40  * Debugging: see timer_list.c
  41  */
  42 struct tick_device *tick_get_device(int cpu)
  43 {
  44         return &per_cpu(tick_cpu_device, cpu);
  45 }
  46
  47 /**
  48  * tick_is_oneshot_available - check for a oneshot capable event device
  49  */
  50 int tick_is_oneshot_available(void)
  51 {
  52         struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
  53
  54         return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
  55 }
  56
  57 /*
  58  * Periodic tick
  59  */
  60 static void tick_periodic(int cpu)
  61 {
  62         if (tick_do_timer_cpu == cpu) {
  63                 write_seqlock(&xtime_lock);
  64
  65                 /* Keep track of the next tick event */
  66                 tick_next_period = ktime_add(tick_next_period, tick_period);
  67
  68                 do_timer(1);
  69                 write_sequnlock(&xtime_lock);
  70         }
  71
  72         update_process_times(user_mode(get_irq_regs()));
  73         profile_tick(CPU_PROFILING);
  74 }
  75
  76 /*
  77  * Event handler for periodic ticks
  78  */
  79 void tick_handle_periodic(struct clock_event_device *dev)
  80 {
  81         int cpu = smp_processor_id();
  82         ktime_t next;
  83
  84         tick_periodic(cpu);
  85
  86         if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
  87                 return;
  88         /*
  89          * Setup the next period for devices, which do not have
  90          * periodic mode:
  91          */
  92         next = ktime_add(dev->next_event, tick_period);
  93         for (;;) {
  94                 if (!clockevents_program_event(dev, next, ktime_get()))
  95                         return;
  96                 tick_periodic(cpu);
  97                 next = ktime_add(next, tick_period);
  98         }
  99 }
 100
 101 /*
 102  * Setup the device for a periodic tick
 103  */
 104 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
 105 {
 106         tick_set_periodic_handler(dev, broadcast);
 107
 108         /* Broadcast setup ? */
 109         if (!tick_device_is_functional(dev))
 110                 return;
 111
 112         if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
 113             !tick_broadcast_oneshot_active()) {
 114                 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
 115         } else {
 116                 unsigned long seq;
 117                 ktime_t next;
 118
 119                 do {
 120                         seq = read_seqbegin(&xtime_lock);
 121                         next = tick_next_period;
 122                 } while (read_seqretry(&xtime_lock, seq));
 123
 124                 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 125
 126                 for (;;) {
 127                         if (!clockevents_program_event(dev, next, ktime_get()))
 128                                 return;
 129                         next = ktime_add(next, tick_period);
 130                 }
 131         }
 132 }
 133
 134 /*
 135  * Setup the tick device
 136  */
 137 static void tick_setup_device(struct tick_device *td,
 138                               struct clock_event_device *newdev, int cpu,
 139                               const struct cpumask *cpumask)
 140 {
 141         ktime_t next_event;
 142         void (*handler)(struct clock_event_device *) = NULL;
 143
 144         /*
 145          * First device setup ?
 146          */
 147         if (!td->evtdev) {
 148                 /*
 149                  * If no cpu took the do_timer update, assign it to
 150                  * this cpu:
 151                  */
 152                 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
 153                         tick_do_timer_cpu = cpu;
 154                         tick_next_period = ktime_get();
 155                         tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
 156                 }
 157
 158                 /*
 159                  * Startup in periodic mode first.
 160                  */
 161                 td->mode = TICKDEV_MODE_PERIODIC;
 162         } else {
 163                 handler = td->evtdev->event_handler;
 164                 next_event = td->evtdev->next_event;
 165                 td->evtdev->event_handler = clockevents_handle_noop;
 166         }
 167
 168         td->evtdev = newdev;
 169
 170         /*
 171          * When the device is not per cpu, pin the interrupt to the
 172          * current cpu:
 173          */
 174         if (!cpumask_equal(newdev->cpumask, cpumask))
 175                 irq_set_affinity(newdev->irq, cpumask);
 176
 177         /*
 178          * When global broadcasting is active, check if the current
 179          * device is registered as a placeholder for broadcast mode.
 180          * This allows us to handle this x86 misfeature in a generic
 181          * way.
 182          */
 183         if (tick_device_uses_broadcast(newdev, cpu))
 184                 return;
 185
 186         if (td->mode == TICKDEV_MODE_PERIODIC)
 187                 tick_setup_periodic(newdev, 0);
 188         else
 189                 tick_setup_oneshot(newdev, handler, next_event);
 190 }
 191
 192 /*
 193  * Check, if the new registered device should be used.
 194  */
 195 static int tick_check_new_device(struct clock_event_device *newdev)
 196 {
 197         struct clock_event_device *curdev;
 198         struct tick_device *td;
 199         int cpu, ret = NOTIFY_OK;
 200         unsigned long flags;
 201
 202         spin_lock_irqsave(&tick_device_lock, flags);
 203
 204         cpu = smp_processor_id();
 205         if (!cpumask_test_cpu(cpu, newdev->cpumask))
 206                 goto out_bc;
 207
 208         td = &per_cpu(tick_cpu_device, cpu);
 209         curdev = td->evtdev;
 210
 211         /* cpu local device ? */
 212         if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) {
 213
 214                 /*
 215                  * If the cpu affinity of the device interrupt can not
 216                  * be set, ignore it.
 217                  */
 218                 if (!irq_can_set_affinity(newdev->irq))
 219                         goto out_bc;
 220
 221                 /*
 222                  * If we have a cpu local device already, do not replace it
 223                  * by a non cpu local device
 224                  */
 225                 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
 226                         goto out_bc;
 227         }
 228
 229         /*
 230          * If we have an active device, then check the rating and the oneshot
 231          * feature.
 232          */
 233         if (curdev) {
 234                 /*
 235                  * Prefer one shot capable devices !
 236                  */
 237                 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
 238                     !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
 239                         goto out_bc;
 240                 /*
 241                  * Check the rating
 242                  */
 243                 if (curdev->rating >= newdev->rating)
 244                         goto out_bc;
 245         }
 246
 247         /*
 248          * Replace the eventually existing device by the new
 249          * device. If the current device is the broadcast device, do
 250          * not give it back to the clockevents layer !
 251          */
 252         if (tick_is_broadcast_device(curdev)) {
 253                 clockevents_shutdown(curdev);
 254                 curdev = NULL;
 255         }
 256         clockevents_exchange_device(curdev, newdev);
 257         tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
 258         if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
 259                 tick_oneshot_notify();
 260
 261         spin_unlock_irqrestore(&tick_device_lock, flags);
 262         return NOTIFY_STOP;
 263
 264 out_bc:
 265         /*
 266          * Can the new device be used as a broadcast device ?
 267          */
 268         if (tick_check_broadcast_device(newdev))
 269                 ret = NOTIFY_STOP;
 270
 271         spin_unlock_irqrestore(&tick_device_lock, flags);
 272
 273         return ret;
 274 }
 275
 276 /*
 277  * Transfer the do_timer job away from a dying cpu.
 278  *
 279  * Called with interrupts disabled.
 280  */
 281 static void tick_handover_do_timer(int *cpup)
 282 {
 283         if (*cpup == tick_do_timer_cpu) {
 284                 int cpu = cpumask_first(cpu_online_mask);
 285
 286                 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
 287                         TICK_DO_TIMER_NONE;
 288         }
 289 }
 290
 291 /*
 292  * Shutdown an event device on a given cpu:
 293  *
 294  * This is called on a life CPU, when a CPU is dead. So we cannot
 295  * access the hardware device itself.
 296  * We just set the mode and remove it from the lists.
 297  */
 298 static void tick_shutdown(unsigned int *cpup)
 299 {
 300         struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
 301         struct clock_event_device *dev = td->evtdev;
 302         unsigned long flags;
 303
 304         spin_lock_irqsave(&tick_device_lock, flags);
 305         td->mode = TICKDEV_MODE_PERIODIC;
 306         if (dev) {
 307                 /*
 308                  * Prevent that the clock events layer tries to call
 309                  * the set mode function!
 310                  */
 311                 dev->mode = CLOCK_EVT_MODE_UNUSED;
 312                 clockevents_exchange_device(dev, NULL);
 313                 td->evtdev = NULL;
 314         }
 315         spin_unlock_irqrestore(&tick_device_lock, flags);
 316 }
 317
 318 static void tick_suspend(void)
 319 {
 320         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
 321         unsigned long flags;
 322
 323         spin_lock_irqsave(&tick_device_lock, flags);
 324         clockevents_shutdown(td->evtdev);
 325         spin_unlock_irqrestore(&tick_device_lock, flags);
 326 }
 327
 328 static void tick_resume(void)
 329 {
 330         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
 331         unsigned long flags;
 332         int broadcast = tick_resume_broadcast();
 333
 334         spin_lock_irqsave(&tick_device_lock, flags);
 335         clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
 336
 337         if (!broadcast) {
 338                 if (td->mode == TICKDEV_MODE_PERIODIC)
 339                         tick_setup_periodic(td->evtdev, 0);
 340                 else
 341                         tick_resume_oneshot();
 342         }
 343         spin_unlock_irqrestore(&tick_device_lock, flags);
 344 }
 345
 346 /*
 347  * Notification about clock event devices
 348  */
 349 static int tick_notify(struct notifier_block *nb, unsigned long reason,
 350                                void *dev)
 351 {
 352         switch (reason) {
 353
 354         case CLOCK_EVT_NOTIFY_ADD:
 355                 return tick_check_new_device(dev);
 356
 357         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 358         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 359         case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 360                 tick_broadcast_on_off(reason, dev);
 361                 break;
 362
 363         case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
 364         case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
 365                 tick_broadcast_oneshot_control(reason);
 366                 break;
 367
 368         case CLOCK_EVT_NOTIFY_CPU_DYING:
 369                 tick_handover_do_timer(dev);
 370                 break;
 371
 372         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 373                 tick_shutdown_broadcast_oneshot(dev);
 374                 tick_shutdown_broadcast(dev);
 375                 tick_shutdown(dev);
 376                 break;
 377
 378         case CLOCK_EVT_NOTIFY_SUSPEND:
 379                 tick_suspend();
 380                 tick_suspend_broadcast();
 381                 break;
 382
 383         case CLOCK_EVT_NOTIFY_RESUME:
 384                 tick_resume();
 385                 break;
 386
 387         default:
 388                 break;
 389         }
 390
 391         return NOTIFY_OK;
 392 }
 393
 394 static struct notifier_block tick_notifier = {
 395         .notifier_call = tick_notify,
 396 };
 397
 398 /**
 399  * tick_init - initialize the tick control
 400  *
 401  * Register the notifier with the clockevents framework
 402  */
 403 void __init tick_init(void)
 404 {
 405         clockevents_register_notifier(&tick_notifier);
 406 }