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 static int tick_do_timer_cpu = -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
  81         tick_periodic(cpu);
  82
  83         if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
  84                 return;
  85         /*
  86          * Setup the next period for devices, which do not have
  87          * periodic mode:
  88          */
  89         for (;;) {
  90                 ktime_t next = ktime_add(dev->next_event, tick_period);
  91
  92                 if (!clockevents_program_event(dev, next, ktime_get()))
  93                         return;
  94                 tick_periodic(cpu);
  95         }
  96 }
  97
  98 /*
  99  * Setup the device for a periodic tick
 100  */
 101 void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
 102 {
 103         tick_set_periodic_handler(dev, broadcast);
 104
 105         /* Broadcast setup ? */
 106         if (!tick_device_is_functional(dev))
 107                 return;
 108
 109         if (dev->features & CLOCK_EVT_FEAT_PERIODIC) {
 110                 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
 111         } else {
 112                 unsigned long seq;
 113                 ktime_t next;
 114
 115                 do {
 116                         seq = read_seqbegin(&xtime_lock);
 117                         next = tick_next_period;
 118                 } while (read_seqretry(&xtime_lock, seq));
 119
 120                 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
 121
 122                 for (;;) {
 123                         if (!clockevents_program_event(dev, next, ktime_get()))
 124                                 return;
 125                         next = ktime_add(next, tick_period);
 126                 }
 127         }
 128 }
 129
 130 /*
 131  * Setup the tick device
 132  */
 133 static void tick_setup_device(struct tick_device *td,
 134                               struct clock_event_device *newdev, int cpu,
 135                               cpumask_t cpumask)
 136 {
 137         ktime_t next_event;
 138         void (*handler)(struct clock_event_device *) = NULL;
 139
 140         /*
 141          * First device setup ?
 142          */
 143         if (!td->evtdev) {
 144                 /*
 145                  * If no cpu took the do_timer update, assign it to
 146                  * this cpu:
 147                  */
 148                 if (tick_do_timer_cpu == -1) {
 149                         tick_do_timer_cpu = cpu;
 150                         tick_next_period = ktime_get();
 151                         tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
 152                 }
 153
 154                 /*
 155                  * Startup in periodic mode first.
 156                  */
 157                 td->mode = TICKDEV_MODE_PERIODIC;
 158         } else {
 159                 handler = td->evtdev->event_handler;
 160                 next_event = td->evtdev->next_event;
 161         }
 162
 163         td->evtdev = newdev;
 164
 165         /*
 166          * When the device is not per cpu, pin the interrupt to the
 167          * current cpu:
 168          */
 169         if (!cpus_equal(newdev->cpumask, cpumask))
 170                 irq_set_affinity(newdev->irq, cpumask);
 171
 172         /*
 173          * When global broadcasting is active, check if the current
 174          * device is registered as a placeholder for broadcast mode.
 175          * This allows us to handle this x86 misfeature in a generic
 176          * way.
 177          */
 178         if (tick_device_uses_broadcast(newdev, cpu))
 179                 return;
 180
 181         if (td->mode == TICKDEV_MODE_PERIODIC)
 182                 tick_setup_periodic(newdev, 0);
 183         else
 184                 tick_setup_oneshot(newdev, handler, next_event);
 185 }
 186
 187 /*
 188  * Check, if the new registered device should be used.
 189  */
 190 static int tick_check_new_device(struct clock_event_device *newdev)
 191 {
 192         struct clock_event_device *curdev;
 193         struct tick_device *td;
 194         int cpu, ret = NOTIFY_OK;
 195         unsigned long flags;
 196         cpumask_t cpumask;
 197
 198         spin_lock_irqsave(&tick_device_lock, flags);
 199
 200         cpu = smp_processor_id();
 201         if (!cpu_isset(cpu, newdev->cpumask))
 202                 goto out;
 203
 204         td = &per_cpu(tick_cpu_device, cpu);
 205         curdev = td->evtdev;
 206         cpumask = cpumask_of_cpu(cpu);
 207
 208         /* cpu local device ? */
 209         if (!cpus_equal(newdev->cpumask, cpumask)) {
 210
 211                 /*
 212                  * If the cpu affinity of the device interrupt can not
 213                  * be set, ignore it.
 214                  */
 215                 if (!irq_can_set_affinity(newdev->irq))
 216                         goto out_bc;
 217
 218                 /*
 219                  * If we have a cpu local device already, do not replace it
 220                  * by a non cpu local device
 221                  */
 222                 if (curdev && cpus_equal(curdev->cpumask, cpumask))
 223                         goto out_bc;
 224         }
 225
 226         /*
 227          * If we have an active device, then check the rating and the oneshot
 228          * feature.
 229          */
 230         if (curdev) {
 231                 /*
 232                  * Prefer one shot capable devices !
 233                  */
 234                 if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
 235                     !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
 236                         goto out_bc;
 237                 /*
 238                  * Check the rating
 239                  */
 240                 if (curdev->rating >= newdev->rating)
 241                         goto out_bc;
 242         }
 243
 244         /*
 245          * Replace the eventually existing device by the new
 246          * device. If the current device is the broadcast device, do
 247          * not give it back to the clockevents layer !
 248          */
 249         if (tick_is_broadcast_device(curdev)) {
 250                 clockevents_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN);
 251                 curdev = NULL;
 252         }
 253         clockevents_exchange_device(curdev, newdev);
 254         tick_setup_device(td, newdev, cpu, cpumask);
 255         if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
 256                 tick_oneshot_notify();
 257
 258         spin_unlock_irqrestore(&tick_device_lock, flags);
 259         return NOTIFY_STOP;
 260
 261 out_bc:
 262         /*
 263          * Can the new device be used as a broadcast device ?
 264          */
 265         if (tick_check_broadcast_device(newdev))
 266                 ret = NOTIFY_STOP;
 267 out:
 268         spin_unlock_irqrestore(&tick_device_lock, flags);
 269
 270         return ret;
 271 }
 272
 273 /*
 274  * Shutdown an event device on a given cpu:
 275  *
 276  * This is called on a life CPU, when a CPU is dead. So we cannot
 277  * access the hardware device itself.
 278  * We just set the mode and remove it from the lists.
 279  */
 280 static void tick_shutdown(unsigned int *cpup)
 281 {
 282         struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
 283         struct clock_event_device *dev = td->evtdev;
 284         unsigned long flags;
 285
 286         spin_lock_irqsave(&tick_device_lock, flags);
 287         td->mode = TICKDEV_MODE_PERIODIC;
 288         if (dev) {
 289                 /*
 290                  * Prevent that the clock events layer tries to call
 291                  * the set mode function!
 292                  */
 293                 dev->mode = CLOCK_EVT_MODE_UNUSED;
 294                 clockevents_exchange_device(dev, NULL);
 295                 td->evtdev = NULL;
 296         }
 297         spin_unlock_irqrestore(&tick_device_lock, flags);
 298 }
 299
 300 /*
 301  * Notification about clock event devices
 302  */
 303 static int tick_notify(struct notifier_block *nb, unsigned long reason,
 304                                void *dev)
 305 {
 306         switch (reason) {
 307
 308         case CLOCK_EVT_NOTIFY_ADD:
 309                 return tick_check_new_device(dev);
 310
 311         case CLOCK_EVT_NOTIFY_BROADCAST_ON:
 312         case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
 313                 tick_broadcast_on_off(reason, dev);
 314                 break;
 315
 316         case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
 317         case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
 318                 tick_broadcast_oneshot_control(reason);
 319                 break;
 320
 321         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 322                 tick_shutdown_broadcast_oneshot(dev);
 323                 tick_shutdown_broadcast(dev);
 324                 tick_shutdown(dev);
 325                 break;
 326
 327         default:
 328                 break;
 329         }
 330
 331         return NOTIFY_OK;
 332 }
 333
 334 static struct notifier_block tick_notifier = {
 335         .notifier_call = tick_notify,
 336 };
 337
 338 /**
 339  * tick_init - initialize the tick control
 340  *
 341  * Register the notifier with the clockevents framework
 342  */
 343 void __init tick_init(void)
 344 {
 345         clockevents_register_notifier(&tick_notifier);
 346 }