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
  22 #include <asm/irq_regs.h>
  23
  24 #include "tick-internal.h"
  25
  26 /*
  27  * Tick devices
  28  */
  29 DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
  30 /*
  31  * Tick next event: keeps track of the tick time
  32  */
  33 ktime_t tick_next_period;
  34 ktime_t tick_period;
  35 int tick_do_timer_cpu __read_mostly = TICK_DO_TIMER_BOOT;
  36 static DEFINE_RAW_SPINLOCK(tick_device_lock);
  37
  38 /*
  39  * Debugging: see timer_list.c
  40  */
  41 struct tick_device *tick_get_device(int cpu)
  42 {
  43         return &per_cpu(tick_cpu_device, cpu);
  44 }
  45
  46 /**
  47  * tick_is_oneshot_available - check for a oneshot capable event device
  48  */
  49 int tick_is_oneshot_available(void)
  50 {
  51         struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
  52
  53         if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
  54                 return 0;
  55         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
  56                 return 1;
  57         return tick_broadcast_oneshot_available();
  58 }
  59
  60 /*
  61  * Periodic tick
  62  */
  63 static void tick_periodic(int cpu)
  64 {
  65         if (tick_do_timer_cpu == cpu) {
  66                 write_seqlock(&xtime_lock);
  67
  68                 /* Keep track of the next tick event */
  69                 tick_next_period = ktime_add(tick_next_period, tick_period);
  70
  71                 do_timer(1);
  72                 write_sequnlock(&xtime_lock);
  73         }
  74
  75         update_process_times(user_mode(get_irq_regs()));
  76         profile_tick(CPU_PROFILING);
  77 }
  78
  79 /*
  80  * Event handler for periodic ticks
  81  */
  82 void tick_handle_periodic(struct clock_event_device *dev)
  83 {
  84         int cpu = smp_processor_id();
  85         ktime_t next;
  86
  87         tick_periodic(cpu);
  88
  89         if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
  90                 return;
  91         /*
  92          * Setup the next period for devices, which do not have
  93          * periodic mode:
  94          */
  95         next = ktime_add(dev->next_event, tick_period);
  96         for (;;) {
  97                 if (!clockevents_program_event(dev, next, false))
  98                         return;
  99                 /*
 100                  * Have to be careful here. If we're in oneshot mode,
 101                  * before we call tick_periodic() in a loop, we need
 102                  * to be sure we're using a real hardware clocksource.
 103                  * Otherwise we could get trapped in an infinite
 104                  * loop, as the tick_periodic() increments jiffies,
 105                  * when then will increment time, posibly causing
 106                  * the loop to trigger again and again.
 107                  */
 108                 if (timekeeping_valid_for_hres())
 109                         tick_periodic(cpu);
 110                 next = ktime_add(next, tick_period);
 111         }
 112 }
 113
 114 /*
 115  * Setup the device for a periodic tick
 116  */
 117 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
 118 {
 119         tick_set_periodic_handler(dev, broadcast);
 120
 121         /* Broadcast setup ? */
 122         if (!tick_device_is_functional(dev))
 123                 return;
 124
 125         if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
 126             !tick_broadcast_oneshot_active()) {
 127                 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
 128         } else {
 129                 unsigned long seq;
 130                 ktime_t next;
 131
 132                 do {
 133                         seq = read_seqbegin(&xtime_lock);
 134                         next = tick_next_period;
 135                 } while (read_seqretry(&xtime_lock, seq));
 136
 137                 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 138
 139                 for (;;) {
 140                         if (!clockevents_program_event(dev, next, false))
 141                                 return;
 142                         next = ktime_add(next, tick_period);
 143                 }
 144         }
 145 }
 146
 147 /*
 148  * Setup the tick device
 149  */
 150 static void tick_setup_device(struct tick_device *td,
 151                               struct clock_event_device *newdev, int cpu,
 152                               const struct cpumask *cpumask)
 153 {
 154         ktime_t next_event;
 155         void (*handler)(struct clock_event_device *) = NULL;
 156
 157         /*
 158          * First device setup ?
 159          */
 160         if (!td->evtdev) {
 161                 /*
 162                  * If no cpu took the do_timer update, assign it to
 163                  * this cpu:
 164                  */
 165                 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
 166                         tick_do_timer_cpu = cpu;
 167                         tick_next_period = ktime_get();
 168                         tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
 169                 }
 170
 171                 /*
 172                  * Startup in periodic mode first.
 173                  */
 174                 td->mode = TICKDEV_MODE_PERIODIC;
 175         } else {
 176                 handler = td->evtdev->event_handler;
 177                 next_event = td->evtdev->next_event;
 178                 td->evtdev->event_handler = clockevents_handle_noop;
 179         }
 180
 181         td->evtdev = newdev;
 182
 183         /*
 184          * When the device is not per cpu, pin the interrupt to the
 185          * current cpu:
 186          */
 187         if (!cpumask_equal(newdev->cpumask, cpumask))
 188                 irq_set_affinity(newdev->irq, cpumask);
 189
 190         /*
 191          * When global broadcasting is active, check if the current
 192          * device is registered as a placeholder for broadcast mode.
 193          * This allows us to handle this x86 misfeature in a generic
 194          * way.
 195          */
 196         if (tick_device_uses_broadcast(newdev, cpu))
 197                 return;
 198
 199         if (td->mode == TICKDEV_MODE_PERIODIC)
 200                 tick_setup_periodic(newdev, 0);
 201         else
 202                 tick_setup_oneshot(newdev, handler, next_event);
 203 }
 204
 205 /*
 206  * Check, if the new registered device should be used.
 207  */
 208 static int tick_check_new_device(struct clock_event_device *newdev)
 209 {
 210         struct clock_event_device *curdev;
 211         struct tick_device *td;
 212         int cpu, ret = NOTIFY_OK;
 213         unsigned long flags;
 214
 215         raw_spin_lock_irqsave(&tick_device_lock, flags);
 216
 217         cpu = smp_processor_id();
 218         if (!cpumask_test_cpu(cpu, newdev->cpumask))
 219                 goto out_bc;
 220
 221         td = &per_cpu(tick_cpu_device, cpu);
 222         curdev = td->evtdev;
 223
 224         /* cpu local device ? */
 225         if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) {
 226
 227                 /*
 228                  * If the cpu affinity of the device interrupt can not
 229                  * be set, ignore it.
 230                  */
 231                 if (!irq_can_set_affinity(newdev->irq))
 232                         goto out_bc;
 233
 234                 /*
 235                  * If we have a cpu local device already, do not replace it
 236                  * by a non cpu local device
 237                  */
 238                 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
 239                         goto out_bc;
 240         }
 241
 242         /*
 243          * If we have an active device, then check the rating and the oneshot
 244          * feature.
 245          */
 246         if (curdev) {
 247                 /*
 248                  * Prefer one shot capable devices !
 249                  */
 250                 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
 251                     !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
 252                         goto out_bc;
 253                 /*
 254                  * Check the rating
 255                  */
 256                 if (curdev->rating >= newdev->rating)
 257                         goto out_bc;
 258         }
 259
 260         /*
 261          * Replace the eventually existing device by the new
 262          * device. If the current device is the broadcast device, do
 263          * not give it back to the clockevents layer !
 264          */
 265         if (tick_is_broadcast_device(curdev)) {
 266                 clockevents_shutdown(curdev);
 267                 curdev = NULL;
 268         }
 269         clockevents_exchange_device(curdev, newdev);
 270         tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
 271         if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
 272                 tick_oneshot_notify();
 273
 274         raw_spin_unlock_irqrestore(&tick_device_lock, flags);
 275         return NOTIFY_STOP;
 276
 277 out_bc:
 278         /*
 279          * Can the new device be used as a broadcast device ?
 280          */
 281         if (tick_check_broadcast_device(newdev))
 282                 ret = NOTIFY_STOP;
 283
 284         raw_spin_unlock_irqrestore(&tick_device_lock, flags);
 285
 286         return ret;
 287 }
 288
 289 /*
 290  * Transfer the do_timer job away from a dying cpu.
 291  *
 292  * Called with interrupts disabled.
 293  */
 294 static void tick_handover_do_timer(int *cpup)
 295 {
 296         if (*cpup == tick_do_timer_cpu) {
 297                 int cpu = cpumask_first(cpu_online_mask);
 298
 299                 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
 300                         TICK_DO_TIMER_NONE;
 301         }
 302 }
 303
 304 /*
 305  * Shutdown an event device on a given cpu:
 306  *
 307  * This is called on a life CPU, when a CPU is dead. So we cannot
 308  * access the hardware device itself.
 309  * We just set the mode and remove it from the lists.
 310  */
 311 static void tick_shutdown(unsigned int *cpup)
 312 {
 313         struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
 314         struct clock_event_device *dev = td->evtdev;
 315         unsigned long flags;
 316
 317         raw_spin_lock_irqsave(&tick_device_lock, flags);
 318         td->mode = TICKDEV_MODE_PERIODIC;
 319         if (dev) {
 320                 /*
 321                  * Prevent that the clock events layer tries to call
 322                  * the set mode function!
 323                  */
 324                 dev->mode = CLOCK_EVT_MODE_UNUSED;
 325                 clockevents_exchange_device(dev, NULL);
 326                 td->evtdev = NULL;
 327         }
 328         raw_spin_unlock_irqrestore(&tick_device_lock, flags);
 329 }
 330
 331 static void tick_suspend(void)
 332 {
 333         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
 334         unsigned long flags;
 335
 336         raw_spin_lock_irqsave(&tick_device_lock, flags);
 337         clockevents_shutdown(td->evtdev);
 338         raw_spin_unlock_irqrestore(&tick_device_lock, flags);
 339 }
 340
 341 static void tick_resume(void)
 342 {
 343         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
 344         unsigned long flags;
 345         int broadcast = tick_resume_broadcast();
 346
 347         raw_spin_lock_irqsave(&tick_device_lock, flags);
 348         clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
 349
 350         if (!broadcast) {
 351                 if (td->mode == TICKDEV_MODE_PERIODIC)
 352                         tick_setup_periodic(td->evtdev, 0);
 353                 else
 354                         tick_resume_oneshot();
 355         }
 356         raw_spin_unlock_irqrestore(&tick_device_lock, flags);
 357 }
 358
 359 /*
 360  * Notification about clock event devices
 361  */
 362 static int tick_notify(struct notifier_block *nb, unsigned long reason,
 363                                void *dev)
 364 {
 365         switch (reason) {
 366
 367         case CLOCK_EVT_NOTIFY_ADD:
 368                 return tick_check_new_device(dev);
 369
 370         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 371         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 372         case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 373                 tick_broadcast_on_off(reason, dev);
 374                 break;
 375
 376         case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
 377         case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
 378                 tick_broadcast_oneshot_control(reason);
 379                 break;
 380
 381         case CLOCK_EVT_NOTIFY_CPU_DYING:
 382                 tick_handover_do_timer(dev);
 383                 break;
 384
 385         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 386                 tick_shutdown_broadcast_oneshot(dev);
 387                 tick_shutdown_broadcast(dev);
 388                 tick_shutdown(dev);
 389                 break;
 390
 391         case CLOCK_EVT_NOTIFY_SUSPEND:
 392                 tick_suspend();
 393                 tick_suspend_broadcast();
 394                 break;
 395
 396         case CLOCK_EVT_NOTIFY_RESUME:
 397                 tick_resume();
 398                 break;
 399
 400         default:
 401                 break;
 402         }
 403
 404         return NOTIFY_OK;
 405 }
 406
 407 static struct notifier_block tick_notifier = {
 408         .notifier_call = tick_notify,
 409 };
 410
 411 /**
 412  * tick_init - initialize the tick control
 413  *
 414  * Register the notifier with the clockevents framework
 415  */
 416 void __init tick_init(void)
 417 {
 418         clockevents_register_notifier(&tick_notifier);
 419 }