tick-common.c 8.5 KB

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  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. #include "tick-internal.h"
  23. /*
  24. * Tick devices
  25. */
  26. DEFINE_PER_CPU(struct tick_device, tick_cpu_device);
  27. /*
  28. * Tick next event: keeps track of the tick time
  29. */
  30. ktime_t tick_next_period;
  31. ktime_t tick_period;
  32. int tick_do_timer_cpu __read_mostly = -1;
  33. DEFINE_SPINLOCK(tick_device_lock);
  34. /*
  35. * Debugging: see timer_list.c
  36. */
  37. struct tick_device *tick_get_device(int cpu)
  38. {
  39. return &per_cpu(tick_cpu_device, cpu);
  40. }
  41. /**
  42. * tick_is_oneshot_available - check for a oneshot capable event device
  43. */
  44. int tick_is_oneshot_available(void)
  45. {
  46. struct clock_event_device *dev = __get_cpu_var(tick_cpu_device).evtdev;
  47. return dev && (dev->features & CLOCK_EVT_FEAT_ONESHOT);
  48. }
  49. /*
  50. * Periodic tick
  51. */
  52. static void tick_periodic(int cpu)
  53. {
  54. if (tick_do_timer_cpu == cpu) {
  55. write_seqlock(&xtime_lock);
  56. /* Keep track of the next tick event */
  57. tick_next_period = ktime_add(tick_next_period, tick_period);
  58. do_timer(1);
  59. write_sequnlock(&xtime_lock);
  60. }
  61. update_process_times(user_mode(get_irq_regs()));
  62. profile_tick(CPU_PROFILING);
  63. }
  64. /*
  65. * Event handler for periodic ticks
  66. */
  67. void tick_handle_periodic(struct clock_event_device *dev)
  68. {
  69. int cpu = smp_processor_id();
  70. ktime_t next;
  71. tick_periodic(cpu);
  72. if (dev->mode != CLOCK_EVT_MODE_ONESHOT)
  73. return;
  74. /*
  75. * Setup the next period for devices, which do not have
  76. * periodic mode:
  77. */
  78. next = ktime_add(dev->next_event, tick_period);
  79. for (;;) {
  80. if (!clockevents_program_event(dev, next, ktime_get()))
  81. return;
  82. tick_periodic(cpu);
  83. next = ktime_add(next, tick_period);
  84. }
  85. }
  86. /*
  87. * Setup the device for a periodic tick
  88. */
  89. void tick_setup_periodic(struct clock_event_device *dev, int broadcast)
  90. {
  91. tick_set_periodic_handler(dev, broadcast);
  92. /* Broadcast setup ? */
  93. if (!tick_device_is_functional(dev))
  94. return;
  95. if (dev->features & CLOCK_EVT_FEAT_PERIODIC) {
  96. clockevents_set_mode(dev, CLOCK_EVT_MODE_PERIODIC);
  97. } else {
  98. unsigned long seq;
  99. ktime_t next;
  100. do {
  101. seq = read_seqbegin(&xtime_lock);
  102. next = tick_next_period;
  103. } while (read_seqretry(&xtime_lock, seq));
  104. clockevents_set_mode(dev, CLOCK_EVT_MODE_ONESHOT);
  105. for (;;) {
  106. if (!clockevents_program_event(dev, next, ktime_get()))
  107. return;
  108. next = ktime_add(next, tick_period);
  109. }
  110. }
  111. }
  112. /*
  113. * Setup the tick device
  114. */
  115. static void tick_setup_device(struct tick_device *td,
  116. struct clock_event_device *newdev, int cpu,
  117. cpumask_t cpumask)
  118. {
  119. ktime_t next_event;
  120. void (*handler)(struct clock_event_device *) = NULL;
  121. /*
  122. * First device setup ?
  123. */
  124. if (!td->evtdev) {
  125. /*
  126. * If no cpu took the do_timer update, assign it to
  127. * this cpu:
  128. */
  129. if (tick_do_timer_cpu == -1) {
  130. tick_do_timer_cpu = cpu;
  131. tick_next_period = ktime_get();
  132. tick_period = ktime_set(0, NSEC_PER_SEC / HZ);
  133. }
  134. /*
  135. * Startup in periodic mode first.
  136. */
  137. td->mode = TICKDEV_MODE_PERIODIC;
  138. } else {
  139. handler = td->evtdev->event_handler;
  140. next_event = td->evtdev->next_event;
  141. }
  142. td->evtdev = newdev;
  143. /*
  144. * When the device is not per cpu, pin the interrupt to the
  145. * current cpu:
  146. */
  147. if (!cpus_equal(newdev->cpumask, cpumask))
  148. irq_set_affinity(newdev->irq, cpumask);
  149. /*
  150. * When global broadcasting is active, check if the current
  151. * device is registered as a placeholder for broadcast mode.
  152. * This allows us to handle this x86 misfeature in a generic
  153. * way.
  154. */
  155. if (tick_device_uses_broadcast(newdev, cpu))
  156. return;
  157. if (td->mode == TICKDEV_MODE_PERIODIC)
  158. tick_setup_periodic(newdev, 0);
  159. else
  160. tick_setup_oneshot(newdev, handler, next_event);
  161. }
  162. /*
  163. * Check, if the new registered device should be used.
  164. */
  165. static int tick_check_new_device(struct clock_event_device *newdev)
  166. {
  167. struct clock_event_device *curdev;
  168. struct tick_device *td;
  169. int cpu, ret = NOTIFY_OK;
  170. unsigned long flags;
  171. cpumask_t cpumask;
  172. spin_lock_irqsave(&tick_device_lock, flags);
  173. cpu = smp_processor_id();
  174. if (!cpu_isset(cpu, newdev->cpumask))
  175. goto out;
  176. td = &per_cpu(tick_cpu_device, cpu);
  177. curdev = td->evtdev;
  178. cpumask = cpumask_of_cpu(cpu);
  179. /* cpu local device ? */
  180. if (!cpus_equal(newdev->cpumask, cpumask)) {
  181. /*
  182. * If the cpu affinity of the device interrupt can not
  183. * be set, ignore it.
  184. */
  185. if (!irq_can_set_affinity(newdev->irq))
  186. goto out_bc;
  187. /*
  188. * If we have a cpu local device already, do not replace it
  189. * by a non cpu local device
  190. */
  191. if (curdev && cpus_equal(curdev->cpumask, cpumask))
  192. goto out_bc;
  193. }
  194. /*
  195. * If we have an active device, then check the rating and the oneshot
  196. * feature.
  197. */
  198. if (curdev) {
  199. /*
  200. * Prefer one shot capable devices !
  201. */
  202. if ((curdev->features & CLOCK_EVT_FEAT_ONESHOT) &&
  203. !(newdev->features & CLOCK_EVT_FEAT_ONESHOT))
  204. goto out_bc;
  205. /*
  206. * Check the rating
  207. */
  208. if (curdev->rating >= newdev->rating)
  209. goto out_bc;
  210. }
  211. /*
  212. * Replace the eventually existing device by the new
  213. * device. If the current device is the broadcast device, do
  214. * not give it back to the clockevents layer !
  215. */
  216. if (tick_is_broadcast_device(curdev)) {
  217. clockevents_set_mode(curdev, CLOCK_EVT_MODE_SHUTDOWN);
  218. curdev = NULL;
  219. }
  220. clockevents_exchange_device(curdev, newdev);
  221. tick_setup_device(td, newdev, cpu, cpumask);
  222. if (newdev->features & CLOCK_EVT_FEAT_ONESHOT)
  223. tick_oneshot_notify();
  224. spin_unlock_irqrestore(&tick_device_lock, flags);
  225. return NOTIFY_STOP;
  226. out_bc:
  227. /*
  228. * Can the new device be used as a broadcast device ?
  229. */
  230. if (tick_check_broadcast_device(newdev))
  231. ret = NOTIFY_STOP;
  232. out:
  233. spin_unlock_irqrestore(&tick_device_lock, flags);
  234. return ret;
  235. }
  236. /*
  237. * Shutdown an event device on a given cpu:
  238. *
  239. * This is called on a life CPU, when a CPU is dead. So we cannot
  240. * access the hardware device itself.
  241. * We just set the mode and remove it from the lists.
  242. */
  243. static void tick_shutdown(unsigned int *cpup)
  244. {
  245. struct tick_device *td = &per_cpu(tick_cpu_device, *cpup);
  246. struct clock_event_device *dev = td->evtdev;
  247. unsigned long flags;
  248. spin_lock_irqsave(&tick_device_lock, flags);
  249. td->mode = TICKDEV_MODE_PERIODIC;
  250. if (dev) {
  251. /*
  252. * Prevent that the clock events layer tries to call
  253. * the set mode function!
  254. */
  255. dev->mode = CLOCK_EVT_MODE_UNUSED;
  256. clockevents_exchange_device(dev, NULL);
  257. td->evtdev = NULL;
  258. }
  259. /* Transfer the do_timer job away from this cpu */
  260. if (*cpup == tick_do_timer_cpu) {
  261. int cpu = first_cpu(cpu_online_map);
  262. tick_do_timer_cpu = (cpu != NR_CPUS) ? cpu : -1;
  263. }
  264. spin_unlock_irqrestore(&tick_device_lock, flags);
  265. }
  266. static void tick_suspend(void)
  267. {
  268. struct tick_device *td = &__get_cpu_var(tick_cpu_device);
  269. unsigned long flags;
  270. spin_lock_irqsave(&tick_device_lock, flags);
  271. clockevents_set_mode(td->evtdev, CLOCK_EVT_MODE_SHUTDOWN);
  272. spin_unlock_irqrestore(&tick_device_lock, flags);
  273. }
  274. static void tick_resume(void)
  275. {
  276. struct tick_device *td = &__get_cpu_var(tick_cpu_device);
  277. unsigned long flags;
  278. spin_lock_irqsave(&tick_device_lock, flags);
  279. if (td->mode == TICKDEV_MODE_PERIODIC)
  280. tick_setup_periodic(td->evtdev, 0);
  281. else
  282. tick_resume_oneshot();
  283. spin_unlock_irqrestore(&tick_device_lock, flags);
  284. }
  285. /*
  286. * Notification about clock event devices
  287. */
  288. static int tick_notify(struct notifier_block *nb, unsigned long reason,
  289. void *dev)
  290. {
  291. switch (reason) {
  292. case CLOCK_EVT_NOTIFY_ADD:
  293. return tick_check_new_device(dev);
  294. case CLOCK_EVT_NOTIFY_BROADCAST_ON:
  295. case CLOCK_EVT_NOTIFY_BROADCAST_OFF:
  296. tick_broadcast_on_off(reason, dev);
  297. break;
  298. case CLOCK_EVT_NOTIFY_BROADCAST_ENTER:
  299. case CLOCK_EVT_NOTIFY_BROADCAST_EXIT:
  300. tick_broadcast_oneshot_control(reason);
  301. break;
  302. case CLOCK_EVT_NOTIFY_CPU_DEAD:
  303. tick_shutdown_broadcast_oneshot(dev);
  304. tick_shutdown_broadcast(dev);
  305. tick_shutdown(dev);
  306. break;
  307. case CLOCK_EVT_NOTIFY_SUSPEND:
  308. tick_suspend();
  309. tick_suspend_broadcast();
  310. break;
  311. case CLOCK_EVT_NOTIFY_RESUME:
  312. if (!tick_resume_broadcast())
  313. tick_resume();
  314. break;
  315. default:
  316. break;
  317. }
  318. return NOTIFY_OK;
  319. }
  320. static struct notifier_block tick_notifier = {
  321. .notifier_call = tick_notify,
  322. };
  323. /**
  324. * tick_init - initialize the tick control
  325. *
  326. * Register the notifier with the clockevents framework
  327. */
  328. void __init tick_init(void)
  329. {
  330. clockevents_register_notifier(&tick_notifier);
  331. }