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         if (!dev || !(dev->features & CLOCK_EVT_FEAT_ONESHOT))
  55                 return 0;
  56         if (!(dev->features & CLOCK_EVT_FEAT_C3STOP))
  57                 return 1;
  58         return tick_broadcast_oneshot_available();
  59 }
  60
  61 /*
  62  * Periodic tick
  63  */
  64 static void tick_periodic(int cpu)
  65 {
  66         if (tick_do_timer_cpu == cpu) {
  67                 write_seqlock(&xtime_lock);
  68
  69                 /* Keep track of the next tick event */
  70                 tick_next_period = ktime_add(tick_next_period, tick_period);
  71
  72                 do_timer(1);
  73                 write_sequnlock(&xtime_lock);
  74         }
  75
  76         update_process_times(user_mode(get_irq_regs()));
  77         profile_tick(CPU_PROFILING);
  78 }
  79
  80 /*
  81  * Event handler for periodic ticks
  82  */
  83 void tick_handle_periodic(struct clock_event_device *dev)
  84 {
  85         int cpu = smp_processor_id();
  86         ktime_t next;
  87
  88         tick_periodic(cpu);
  89
  90         if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
  91                 return;
  92         /*
  93          * Setup the next period for devices, which do not have
  94          * periodic mode:
  95          */
  96         next = ktime_add(dev->next_event, tick_period);
  97         for (;;) {
  98                 if (!clockevents_program_event(dev, next, ktime_get()))
  99                         return;
 100                 /*
 101                  * Have to be careful here. If we're in oneshot mode,
 102                  * before we call tick_periodic() in a loop, we need
 103                  * to be sure we're using a real hardware clocksource.
 104                  * Otherwise we could get trapped in an infinite
 105                  * loop, as the tick_periodic() increments jiffies,
 106                  * when then will increment time, posibly causing
 107                  * the loop to trigger again and again.
 108                  */
 109                 if (timekeeping_valid_for_hres())
 110                         tick_periodic(cpu);
 111                 next = ktime_add(next, tick_period);
 112         }
 113 }
 114
 115 /*
 116  * Setup the device for a periodic tick
 117  */
 118 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
 119 {
 120         tick_set_periodic_handler(dev, broadcast);
 121
 122         /* Broadcast setup ? */
 123         if (!tick_device_is_functional(dev))
 124                 return;
 125
 126         if ((dev->features & CLOCK_EVT_FEAT_PERIODIC) &&
 127             !tick_broadcast_oneshot_active()) {
 128                 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
 129         } else {
 130                 unsigned long seq;
 131                 ktime_t next;
 132
 133                 do {
 134                         seq = read_seqbegin(&xtime_lock);
 135                         next = tick_next_period;
 136                 } while (read_seqretry(&xtime_lock, seq));
 137
 138                 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 139
 140                 for (;;) {
 141                         if (!clockevents_program_event(dev, next, ktime_get()))
 142                                 return;
 143                         next = ktime_add(next, tick_period);
 144                 }
 145         }
 146 }
 147
 148 /*
 149  * Setup the tick device
 150  */
 151 static void tick_setup_device(struct tick_device *td,
 152                               struct clock_event_device *newdev, int cpu,
 153                               const struct cpumask *cpumask)
 154 {
 155         ktime_t next_event;
 156         void (*handler)(struct clock_event_device *) = NULL;
 157
 158         /*
 159          * First device setup ?
 160          */
 161         if (!td->evtdev) {
 162                 /*
 163                  * If no cpu took the do_timer update, assign it to
 164                  * this cpu:
 165                  */
 166                 if (tick_do_timer_cpu == TICK_DO_TIMER_BOOT) {
 167                         tick_do_timer_cpu = cpu;
 168                         tick_next_period = ktime_get();
 169                         tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
 170                 }
 171
 172                 /*
 173                  * Startup in periodic mode first.
 174                  */
 175                 td->mode = TICKDEV_MODE_PERIODIC;
 176         } else {
 177                 handler = td->evtdev->event_handler;
 178                 next_event = td->evtdev->next_event;
 179                 td->evtdev->event_handler = clockevents_handle_noop;
 180         }
 181
 182         td->evtdev = newdev;
 183
 184         /*
 185          * When the device is not per cpu, pin the interrupt to the
 186          * current cpu:
 187          */
 188         if (!cpumask_equal(newdev->cpumask, cpumask))
 189                 irq_set_affinity(newdev->irq, cpumask);
 190
 191         /*
 192          * When global broadcasting is active, check if the current
 193          * device is registered as a placeholder for broadcast mode.
 194          * This allows us to handle this x86 misfeature in a generic
 195          * way.
 196          */
 197         if (tick_device_uses_broadcast(newdev, cpu))
 198                 return;
 199
 200         if (td->mode == TICKDEV_MODE_PERIODIC)
 201                 tick_setup_periodic(newdev, 0);
 202         else
 203                 tick_setup_oneshot(newdev, handler, next_event);
 204 }
 205
 206 /*
 207  * Check, if the new registered device should be used.
 208  */
 209 static int tick_check_new_device(struct clock_event_device *newdev)
 210 {
 211         struct clock_event_device *curdev;
 212         struct tick_device *td;
 213         int cpu, ret = NOTIFY_OK;
 214         unsigned long flags;
 215
 216         spin_lock_irqsave(&tick_device_lock, flags);
 217
 218         cpu = smp_processor_id();
 219         if (!cpumask_test_cpu(cpu, newdev->cpumask))
 220                 goto out_bc;
 221
 222         td = &per_cpu(tick_cpu_device, cpu);
 223         curdev = td->evtdev;
 224
 225         /* cpu local device ? */
 226         if (!cpumask_equal(newdev->cpumask, cpumask_of(cpu))) {
 227
 228                 /*
 229                  * If the cpu affinity of the device interrupt can not
 230                  * be set, ignore it.
 231                  */
 232                 if (!irq_can_set_affinity(newdev->irq))
 233                         goto out_bc;
 234
 235                 /*
 236                  * If we have a cpu local device already, do not replace it
 237                  * by a non cpu local device
 238                  */
 239                 if (curdev && cpumask_equal(curdev->cpumask, cpumask_of(cpu)))
 240                         goto out_bc;
 241         }
 242
 243         /*
 244          * If we have an active device, then check the rating and the oneshot
 245          * feature.
 246          */
 247         if (curdev) {
 248                 /*
 249                  * Prefer one shot capable devices !
 250                  */
 251                 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
 252                     !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
 253                         goto out_bc;
 254                 /*
 255                  * Check the rating
 256                  */
 257                 if (curdev->rating >= newdev->rating)
 258                         goto out_bc;
 259         }
 260
 261         /*
 262          * Replace the eventually existing device by the new
 263          * device. If the current device is the broadcast device, do
 264          * not give it back to the clockevents layer !
 265          */
 266         if (tick_is_broadcast_device(curdev)) {
 267                 clockevents_shutdown(curdev);
 268                 curdev = NULL;
 269         }
 270         clockevents_exchange_device(curdev, newdev);
 271         tick_setup_device(td, newdev, cpu, cpumask_of(cpu));
 272         if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
 273                 tick_oneshot_notify();
 274
 275         spin_unlock_irqrestore(&tick_device_lock, flags);
 276         return NOTIFY_STOP;
 277
 278 out_bc:
 279         /*
 280          * Can the new device be used as a broadcast device ?
 281          */
 282         if (tick_check_broadcast_device(newdev))
 283                 ret = NOTIFY_STOP;
 284
 285         spin_unlock_irqrestore(&tick_device_lock, flags);
 286
 287         return ret;
 288 }
 289
 290 /*
 291  * Transfer the do_timer job away from a dying cpu.
 292  *
 293  * Called with interrupts disabled.
 294  */
 295 static void tick_handover_do_timer(int *cpup)
 296 {
 297         if (*cpup == tick_do_timer_cpu) {
 298                 int cpu = cpumask_first(cpu_online_mask);
 299
 300                 tick_do_timer_cpu = (cpu < nr_cpu_ids) ? cpu :
 301                         TICK_DO_TIMER_NONE;
 302         }
 303 }
 304
 305 /*
 306  * Shutdown an event device on a given cpu:
 307  *
 308  * This is called on a life CPU, when a CPU is dead. So we cannot
 309  * access the hardware device itself.
 310  * We just set the mode and remove it from the lists.
 311  */
 312 static void tick_shutdown(unsigned int *cpup)
 313 {
 314         struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
 315         struct clock_event_device *dev = td->evtdev;
 316         unsigned long flags;
 317
 318         spin_lock_irqsave(&tick_device_lock, flags);
 319         td->mode = TICKDEV_MODE_PERIODIC;
 320         if (dev) {
 321                 /*
 322                  * Prevent that the clock events layer tries to call
 323                  * the set mode function!
 324                  */
 325                 dev->mode = CLOCK_EVT_MODE_UNUSED;
 326                 clockevents_exchange_device(dev, NULL);
 327                 td->evtdev = NULL;
 328         }
 329         spin_unlock_irqrestore(&tick_device_lock, flags);
 330 }
 331
 332 static void tick_suspend(void)
 333 {
 334         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
 335         unsigned long flags;
 336
 337         spin_lock_irqsave(&tick_device_lock, flags);
 338         clockevents_shutdown(td->evtdev);
 339         spin_unlock_irqrestore(&tick_device_lock, flags);
 340 }
 341
 342 static void tick_resume(void)
 343 {
 344         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
 345         unsigned long flags;
 346         int broadcast = tick_resume_broadcast();
 347
 348         spin_lock_irqsave(&tick_device_lock, flags);
 349         clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
 350
 351         if (!broadcast) {
 352                 if (td->mode == TICKDEV_MODE_PERIODIC)
 353                         tick_setup_periodic(td->evtdev, 0);
 354                 else
 355                         tick_resume_oneshot();
 356         }
 357         spin_unlock_irqrestore(&tick_device_lock, flags);
 358 }
 359
 360 /*
 361  * Notification about clock event devices
 362  */
 363 static int tick_notify(struct notifier_block *nb, unsigned long reason,
 364                                void *dev)
 365 {
 366         switch (reason) {
 367
 368         case CLOCK_EVT_NOTIFY_ADD:
 369                 return tick_check_new_device(dev);
 370
 371         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 372         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 373         case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 374                 tick_broadcast_on_off(reason, dev);
 375                 break;
 376
 377         case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
 378         case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
 379                 tick_broadcast_oneshot_control(reason);
 380                 break;
 381
 382         case CLOCK_EVT_NOTIFY_CPU_DYING:
 383                 tick_handover_do_timer(dev);
 384                 break;
 385
 386         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 387                 tick_shutdown_broadcast_oneshot(dev);
 388                 tick_shutdown_broadcast(dev);
 389                 tick_shutdown(dev);
 390                 break;
 391
 392         case CLOCK_EVT_NOTIFY_SUSPEND:
 393                 tick_suspend();
 394                 tick_suspend_broadcast();
 395                 break;
 396
 397         case CLOCK_EVT_NOTIFY_RESUME:
 398                 tick_resume();
 399                 break;
 400
 401         default:
 402                 break;
 403         }
 404
 405         return NOTIFY_OK;
 406 }
 407
 408 static struct notifier_block tick_notifier = {
 409         .notifier_call = tick_notify,
 410 };
 411
 412 /**
 413  * tick_init - initialize the tick control
 414  *
 415  * Register the notifier with the clockevents framework
 416  */
 417 void __init tick_init(void)
 418 {
 419         clockevents_register_notifier(&tick_notifier);
 420 }