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