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 = -1;
  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                 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
 114         } else {
 115                 unsigned long seq;
 116                 ktime_t next;
 117
 118                 do {
 119                         seq = read_seqbegin(&xtime_lock);
 120                         next = tick_next_period;
 121                 } while (read_seqretry(&xtime_lock, seq));
 122
 123                 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 124
 125                 for (;;) {
 126                         if (!clockevents_program_event(dev, next, ktime_get()))
 127                                 return;
 128                         next = ktime_add(next, tick_period);
 129                 }
 130         }
 131 }
 132
 133 /*
 134  * Setup the tick device
 135  */
 136 static void tick_setup_device(struct tick_device *td,
 137                               struct clock_event_device *newdev, int cpu,
 138                               const cpumask_t *cpumask)
 139 {
 140         ktime_t next_event;
 141         void (*handler)(struct clock_event_device *) = NULL;
 142
 143         /*
 144          * First device setup ?
 145          */
 146         if (!td->evtdev) {
 147                 /*
 148                  * If no cpu took the do_timer update, assign it to
 149                  * this cpu:
 150                  */
 151                 if (tick_do_timer_cpu == -1) {
 152                         tick_do_timer_cpu = cpu;
 153                         tick_next_period = ktime_get();
 154                         tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
 155                 }
 156
 157                 /*
 158                  * Startup in periodic mode first.
 159                  */
 160                 td->mode = TICKDEV_MODE_PERIODIC;
 161         } else {
 162                 handler = td->evtdev->event_handler;
 163                 next_event = td->evtdev->next_event;
 164                 td->evtdev->event_handler = clockevents_handle_noop;
 165         }
 166
 167         td->evtdev = newdev;
 168
 169         /*
 170          * When the device is not per cpu, pin the interrupt to the
 171          * current cpu:
 172          */
 173         if (!cpus_equal(newdev->cpumask, *cpumask))
 174                 irq_set_affinity(newdev->irq, *cpumask);
 175
 176         /*
 177          * When global broadcasting is active, check if the current
 178          * device is registered as a placeholder for broadcast mode.
 179          * This allows us to handle this x86 misfeature in a generic
 180          * way.
 181          */
 182         if (tick_device_uses_broadcast(newdev, cpu))
 183                 return;
 184
 185         if (td->mode == TICKDEV_MODE_PERIODIC)
 186                 tick_setup_periodic(newdev, 0);
 187         else
 188                 tick_setup_oneshot(newdev, handler, next_event);
 189 }
 190
 191 /*
 192  * Check, if the new registered device should be used.
 193  */
 194 static int tick_check_new_device(struct clock_event_device *newdev)
 195 {
 196         struct clock_event_device *curdev;
 197         struct tick_device *td;
 198         int cpu, ret = NOTIFY_OK;
 199         unsigned long flags;
 200
 201         spin_lock_irqsave(&tick_device_lock, flags);
 202
 203         cpu = smp_processor_id();
 204         if (!cpu_isset(cpu, newdev->cpumask))
 205                 goto out_bc;
 206
 207         td = &per_cpu(tick_cpu_device, cpu);
 208         curdev = td->evtdev;
 209
 210         /* cpu local device ? */
 211         if (!cpus_equal(newdev->cpumask, cpumask_of_cpu(cpu))) {
 212
 213                 /*
 214                  * If the cpu affinity of the device interrupt can not
 215                  * be set, ignore it.
 216                  */
 217                 if (!irq_can_set_affinity(newdev->irq))
 218                         goto out_bc;
 219
 220                 /*
 221                  * If we have a cpu local device already, do not replace it
 222                  * by a non cpu local device
 223                  */
 224                 if (curdev && cpus_equal(curdev->cpumask, cpumask_of_cpu(cpu)))
 225                         goto out_bc;
 226         }
 227
 228         /*
 229          * If we have an active device, then check the rating and the oneshot
 230          * feature.
 231          */
 232         if (curdev) {
 233                 /*
 234                  * Prefer one shot capable devices !
 235                  */
 236                 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
 237                     !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
 238                         goto out_bc;
 239                 /*
 240                  * Check the rating
 241                  */
 242                 if (curdev->rating >= newdev->rating)
 243                         goto out_bc;
 244         }
 245
 246         /*
 247          * Replace the eventually existing device by the new
 248          * device. If the current device is the broadcast device, do
 249          * not give it back to the clockevents layer !
 250          */
 251         if (tick_is_broadcast_device(curdev)) {
 252                 clockevents_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN);
 253                 curdev = NULL;
 254         }
 255         clockevents_exchange_device(curdev, newdev);
 256         tick_setup_device(td, newdev, cpu, &cpumask_of_cpu(cpu));
 257         if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
 258                 tick_oneshot_notify();
 259
 260         spin_unlock_irqrestore(&tick_device_lock, flags);
 261         return NOTIFY_STOP;
 262
 263 out_bc:
 264         /*
 265          * Can the new device be used as a broadcast device ?
 266          */
 267         if (tick_check_broadcast_device(newdev))
 268                 ret = NOTIFY_STOP;
 269
 270         spin_unlock_irqrestore(&tick_device_lock, flags);
 271
 272         return ret;
 273 }
 274
 275 /*
 276  * Shutdown an event device on a given cpu:
 277  *
 278  * This is called on a life CPU, when a CPU is dead. So we cannot
 279  * access the hardware device itself.
 280  * We just set the mode and remove it from the lists.
 281  */
 282 static void tick_shutdown(unsigned int *cpup)
 283 {
 284         struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
 285         struct clock_event_device *dev = td->evtdev;
 286         unsigned long flags;
 287
 288         spin_lock_irqsave(&tick_device_lock, flags);
 289         td->mode = TICKDEV_MODE_PERIODIC;
 290         if (dev) {
 291                 /*
 292                  * Prevent that the clock events layer tries to call
 293                  * the set mode function!
 294                  */
 295                 dev->mode = CLOCK_EVT_MODE_UNUSED;
 296                 clockevents_exchange_device(dev, NULL);
 297                 td->evtdev = NULL;
 298         }
 299         /* Transfer the do_timer job away from this cpu */
 300         if (*cpup == tick_do_timer_cpu) {
 301                 int cpu = first_cpu(cpu_online_map);
 302
 303                 tick_do_timer_cpu = (cpu != NR_CPUS) ? cpu : -1;
 304         }
 305         spin_unlock_irqrestore(&tick_device_lock, flags);
 306 }
 307
 308 static void tick_suspend(void)
 309 {
 310         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
 311         unsigned long flags;
 312
 313         spin_lock_irqsave(&tick_device_lock, flags);
 314         clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_SHUTDOWN);
 315         spin_unlock_irqrestore(&tick_device_lock, flags);
 316 }
 317
 318 static void tick_resume(void)
 319 {
 320         struct tick_device *td = &__get_cpu_var(tick_cpu_device);
 321         unsigned long flags;
 322         int broadcast = tick_resume_broadcast();
 323
 324         spin_lock_irqsave(&tick_device_lock, flags);
 325         clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_RESUME);
 326
 327         if (!broadcast) {
 328                 if (td->mode == TICKDEV_MODE_PERIODIC)
 329                         tick_setup_periodic(td->evtdev, 0);
 330                 else
 331                         tick_resume_oneshot();
 332         }
 333         spin_unlock_irqrestore(&tick_device_lock, flags);
 334 }
 335
 336 /*
 337  * Notification about clock event devices
 338  */
 339 static int tick_notify(struct notifier_block *nb, unsigned long reason,
 340                                void *dev)
 341 {
 342         switch (reason) {
 343
 344         case CLOCK_EVT_NOTIFY_ADD:
 345                 return tick_check_new_device(dev);
 346
 347         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 348         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 349         case CLOCK_EVT_NOTIFY_BROADCAST_FORCE:
 350                 tick_broadcast_on_off(reason, dev);
 351                 break;
 352
 353         case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
 354         case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
 355                 tick_broadcast_oneshot_control(reason);
 356                 break;
 357
 358         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 359                 tick_shutdown_broadcast_oneshot(dev);
 360                 tick_shutdown_broadcast(dev);
 361                 tick_shutdown(dev);
 362                 break;
 363
 364         case CLOCK_EVT_NOTIFY_SUSPEND:
 365                 tick_suspend();
 366                 tick_suspend_broadcast();
 367                 break;
 368
 369         case CLOCK_EVT_NOTIFY_RESUME:
 370                 tick_resume();
 371                 break;
 372
 373         default:
 374                 break;
 375         }
 376
 377         return NOTIFY_OK;
 378 }
 379
 380 static struct notifier_block tick_notifier = {
 381         .notifier_call = tick_notify,
 382 };
 383
 384 /**
 385  * tick_init - initialize the tick control
 386  *
 387  * Register the notifier with the clockevents framework
 388  */
 389 void __init tick_init(void)
 390 {
 391         clockevents_register_notifier(&tick_notifier);
 392 }