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 /*
  24  * Tick devices
  25  */
  26 static DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
  27 /*
  28  * Tick next event: keeps track of the tick time
  29  */
  30 static ktime_t tick_next_period;
  31 static ktime_t tick_period;
  32 static int tick_do_timer_cpu = -1;
  33 static DEFINE_SPINLOCK(tick_device_lock);
  34
  35 /*
  36  * Periodic tick
  37  */
  38 static void tick_periodic(int cpu)
  39 {
  40         if (tick_do_timer_cpu == cpu) {
  41                 write_seqlock(&xtime_lock);
  42
  43                 /* Keep track of the next tick event */
  44                 tick_next_period = ktime_add(tick_next_period, tick_period);
  45
  46                 do_timer(1);
  47                 write_sequnlock(&xtime_lock);
  48         }
  49
  50         update_process_times(user_mode(get_irq_regs()));
  51         profile_tick(CPU_PROFILING);
  52 }
  53
  54 /*
  55  * Event handler for periodic ticks
  56  */
  57 void tick_handle_periodic(struct clock_event_device *dev)
  58 {
  59         int cpu = smp_processor_id();
  60
  61         tick_periodic(cpu);
  62
  63         if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
  64                 return;
  65         /*
  66          * Setup the next period for devices, which do not have
  67          * periodic mode:
  68          */
  69         for (;;) {
  70                 ktime_t next = ktime_add(dev->next_event, tick_period);
  71
  72                 if (!clockevents_program_event(dev, next, ktime_get()))
  73                         return;
  74                 tick_periodic(cpu);
  75         }
  76 }
  77
  78 /*
  79  * Setup the device for a periodic tick
  80  */
  81 void tick_setup_periodic(struct clock_event_device *dev)
  82 {
  83         dev->event_handler = tick_handle_periodic;
  84
  85         if (dev->features & CLOCK_EVT_FEAT_PERIODIC) {
  86                 clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
  87         } else {
  88                 unsigned long seq;
  89                 ktime_t next;
  90
  91                 do {
  92                         seq = read_seqbegin(&xtime_lock);
  93                         next = tick_next_period;
  94                 } while (read_seqretry(&xtime_lock, seq));
  95
  96                 clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
  97
  98                 for (;;) {
  99                         if (!clockevents_program_event(dev, next, ktime_get()))
 100                                 return;
 101                         next = ktime_add(next, tick_period);
 102                 }
 103         }
 104 }
 105
 106 /*
 107  * Setup the tick device
 108  */
 109 static void tick_setup_device(struct tick_device *td,
 110                               struct clock_event_device *newdev, int cpu,
 111                               cpumask_t cpumask)
 112 {
 113         ktime_t next_event;
 114         void (*handler)(struct clock_event_device *) = NULL;
 115
 116         /*
 117          * First device setup ?
 118          */
 119         if (!td->evtdev) {
 120                 /*
 121                  * If no cpu took the do_timer update, assign it to
 122                  * this cpu:
 123                  */
 124                 if (tick_do_timer_cpu == -1) {
 125                         tick_do_timer_cpu = cpu;
 126                         tick_next_period = ktime_get();
 127                         tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
 128                 }
 129
 130                 /*
 131                  * Startup in periodic mode first.
 132                  */
 133                 td->mode = TICKDEV_MODE_PERIODIC;
 134         } else {
 135                 handler = td->evtdev->event_handler;
 136                 next_event = td->evtdev->next_event;
 137         }
 138
 139         td->evtdev = newdev;
 140
 141         /*
 142          * When the device is not per cpu, pin the interrupt to the
 143          * current cpu:
 144          */
 145         if (!cpus_equal(newdev->cpumask, cpumask))
 146                 irq_set_affinity(newdev->irq, cpumask);
 147
 148         if (td->mode == TICKDEV_MODE_PERIODIC)
 149                 tick_setup_periodic(newdev, 0);
 150 }
 151
 152 /*
 153  * Check, if the new registered device should be used.
 154  */
 155 static int tick_check_new_device(struct clock_event_device *newdev)
 156 {
 157         struct clock_event_device *curdev;
 158         struct tick_device *td;
 159         int cpu, ret = NOTIFY_OK;
 160         unsigned long flags;
 161         cpumask_t cpumask;
 162
 163         spin_lock_irqsave(&tick_device_lock, flags);
 164
 165         cpu = smp_processor_id();
 166         if (!cpu_isset(cpu, newdev->cpumask))
 167                 goto out;
 168
 169         td = &per_cpu(tick_cpu_device, cpu);
 170         curdev = td->evtdev;
 171         cpumask = cpumask_of_cpu(cpu);
 172
 173         /* cpu local device ? */
 174         if (!cpus_equal(newdev->cpumask, cpumask)) {
 175
 176                 /*
 177                  * If the cpu affinity of the device interrupt can not
 178                  * be set, ignore it.
 179                  */
 180                 if (!irq_can_set_affinity(newdev->irq))
 181                         goto out_bc;
 182
 183                 /*
 184                  * If we have a cpu local device already, do not replace it
 185                  * by a non cpu local device
 186                  */
 187                 if (curdev && cpus_equal(curdev->cpumask, cpumask))
 188                         goto out_bc;
 189         }
 190
 191         /*
 192          * If we have an active device, then check the rating and the oneshot
 193          * feature.
 194          */
 195         if (curdev) {
 196                 /*
 197                  * Check the rating
 198                  */
 199                 if (curdev->rating >= newdev->rating)
 200                         goto out;
 201         }
 202
 203         /*
 204          * Replace the eventually existing device by the new
 205          * device.
 206          */
 207         clockevents_exchange_device(curdev, newdev);
 208         tick_setup_device(td, newdev, cpu, cpumask);
 209         ret = NOTIFY_STOP;
 210
 211 out:
 212         spin_unlock_irqrestore(&tick_device_lock, flags);
 213         return ret;
 214 }
 215
 216 /*
 217  * Shutdown an event device on a given cpu:
 218  *
 219  * This is called on a life CPU, when a CPU is dead. So we cannot
 220  * access the hardware device itself.
 221  * We just set the mode and remove it from the lists.
 222  */
 223 static void tick_shutdown(unsigned int *cpup)
 224 {
 225         struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
 226         struct clock_event_device *dev = td->evtdev;
 227         unsigned long flags;
 228
 229         spin_lock_irqsave(&tick_device_lock, flags);
 230         td->mode = TICKDEV_MODE_PERIODIC;
 231         if (dev) {
 232                 /*
 233                  * Prevent that the clock events layer tries to call
 234                  * the set mode function!
 235                  */
 236                 dev->mode = CLOCK_EVT_MODE_UNUSED;
 237                 clockevents_exchange_device(dev, NULL);
 238                 td->evtdev = NULL;
 239         }
 240         spin_unlock_irqrestore(&tick_device_lock, flags);
 241 }
 242
 243 /*
 244  * Notification about clock event devices
 245  */
 246 static int tick_notify(struct notifier_block *nb, unsigned long reason,
 247                                void *dev)
 248 {
 249         switch (reason) {
 250
 251         case CLOCK_EVT_NOTIFY_ADD:
 252                 return tick_check_new_device(dev);
 253
 254         case CLOCK_EVT_NOTIFY_CPU_DEAD:
 255                 tick_shutdown(dev);
 256                 break;
 257
 258         default:
 259                 break;
 260         }
 261
 262         return NOTIFY_OK;
 263 }
 264
 265 static struct notifier_block tick_notifier = {
 266         .notifier_call = tick_notify,
 267 };
 268
 269 /**
 270  * tick_init - initialize the tick control
 271  *
 272  * Register the notifier with the clockevents framework
 273  */
 274 void __init tick_init(void)
 275 {
 276         clockevents_register_notifier(&tick_notifier);
 277 }