include/linux/hrtimer.h

   1 /*
   2  *  include/linux/hrtimer.h
   3  *
   4  *  hrtimers - High-resolution kernel timers
   5  *
   6  *   Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
   7  *   Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
   8  *
   9  *  data type definitions, declarations, prototypes
  10  *
  11  *  Started by: Thomas Gleixner and Ingo Molnar
  12  *
  13  *  For licencing details see kernel-base/COPYING
  14  */
  15 #ifndef _LINUX_HRTIMER_H
  16 #define _LINUX_HRTIMER_H
  17
  18 #include <linux/rbtree.h>
  19 #include <linux/ktime.h>
  20 #include <linux/init.h>
  21 #include <linux/list.h>
  22 #include <linux/wait.h>
  23
  24 struct hrtimer_clock_base;
  25 struct hrtimer_cpu_base;
  26
  27 /*
  28  * Mode arguments of xxx_hrtimer functions:
  29  */
  30 enum hrtimer_mode {
  31         HRTIMER_MODE_ABS,       /* Time value is absolute */
  32         HRTIMER_MODE_REL,       /* Time value is relative to now */
  33 };
  34
  35 /*
  36  * Return values for the callback function
  37  */
  38 enum hrtimer_restart {
  39         HRTIMER_NORESTART,      /* Timer is not restarted */
  40         HRTIMER_RESTART,        /* Timer must be restarted */
  41 };
  42
  43 /*
  44  * hrtimer callback modes:
  45  *
  46  *      HRTIMER_CB_SOFTIRQ:             Callback must run in softirq context
  47  *      HRTIMER_CB_IRQSAFE:             Callback may run in hardirq context
  48  *      HRTIMER_CB_IRQSAFE_NO_RESTART:  Callback may run in hardirq context and
  49  *                                      does not restart the timer
  50  *      HRTIMER_CB_IRQSAFE_NO_SOFTIRQ:  Callback must run in softirq context
  51  *                                      Special mode for tick emultation
  52  */
  53 enum hrtimer_cb_mode {
  54         HRTIMER_CB_SOFTIRQ,
  55         HRTIMER_CB_IRQSAFE,
  56         HRTIMER_CB_IRQSAFE_NO_RESTART,
  57         HRTIMER_CB_IRQSAFE_NO_SOFTIRQ,
  58 };
  59
  60 /*
  61  * Values to track state of the timer
  62  *
  63  * Possible states:
  64  *
  65  * 0x00         inactive
  66  * 0x01         enqueued into rbtree
  67  * 0x02         callback function running
  68  * 0x04         callback pending (high resolution mode)
  69  *
  70  * Special case:
  71  * 0x03         callback function running and enqueued
  72  *              (was requeued on another CPU)
  73  * The "callback function running and enqueued" status is only possible on
  74  * SMP. It happens for example when a posix timer expired and the callback
  75  * queued a signal. Between dropping the lock which protects the posix timer
  76  * and reacquiring the base lock of the hrtimer, another CPU can deliver the
  77  * signal and rearm the timer. We have to preserve the callback running state,
  78  * as otherwise the timer could be removed before the softirq code finishes the
  79  * the handling of the timer.
  80  *
  81  * The HRTIMER_STATE_ENQUEUE bit is always or'ed to the current state to
  82  * preserve the HRTIMER_STATE_CALLBACK bit in the above scenario.
  83  *
  84  * All state transitions are protected by cpu_base->lock.
  85  */
  86 #define HRTIMER_STATE_INACTIVE  0x00
  87 #define HRTIMER_STATE_ENQUEUED  0x01
  88 #define HRTIMER_STATE_CALLBACK  0x02
  89 #define HRTIMER_STATE_PENDING   0x04
  90
  91 /**
  92  * struct hrtimer - the basic hrtimer structure
  93  * @node:       red black tree node for time ordered insertion
  94  * @expires:    the absolute expiry time in the hrtimers internal
  95  *              representation. The time is related to the clock on
  96  *              which the timer is based.
  97  * @function:   timer expiry callback function
  98  * @base:       pointer to the timer base (per cpu and per clock)
  99  * @state:      state information (See bit values above)
 100  * @cb_mode:    high resolution timer feature to select the callback execution
 101  *               mode
 102  * @cb_entry:   list head to enqueue an expired timer into the callback list
 103  * @start_site: timer statistics field to store the site where the timer
 104  *              was started
 105  * @start_comm: timer statistics field to store the name of the process which
 106  *              started the timer
 107  * @start_pid: timer statistics field to store the pid of the task which
 108  *              started the timer
 109  *
 110  * The hrtimer structure must be initialized by hrtimer_init()
 111  */
 112 struct hrtimer {
 113         struct rb_node                  node;
 114         ktime_t                         expires;
 115         enum hrtimer_restart            (*function)(struct hrtimer *);
 116         struct hrtimer_clock_base       *base;
 117         unsigned long                   state;
 118 #ifdef CONFIG_HIGH_RES_TIMERS
 119         enum hrtimer_cb_mode            cb_mode;
 120         struct list_head                cb_entry;
 121 #endif
 122 #ifdef CONFIG_TIMER_STATS
 123         void                            *start_site;
 124         char                            start_comm[16];
 125         int                             start_pid;
 126 #endif
 127 };
 128
 129 /**
 130  * struct hrtimer_sleeper - simple sleeper structure
 131  * @timer:      embedded timer structure
 132  * @task:       task to wake up
 133  *
 134  * task is set to NULL, when the timer expires.
 135  */
 136 struct hrtimer_sleeper {
 137         struct hrtimer timer;
 138         struct task_struct *task;
 139 };
 140
 141 /**
 142  * struct hrtimer_base - the timer base for a specific clock
 143  * @index:              clock type index for per_cpu support when moving a
 144  *                      timer to a base on another cpu.
 145  * @active:             red black tree root node for the active timers
 146  * @first:              pointer to the timer node which expires first
 147  * @resolution:         the resolution of the clock, in nanoseconds
 148  * @get_time:           function to retrieve the current time of the clock
 149  * @get_softirq_time:   function to retrieve the current time from the softirq
 150  * @softirq_time:       the time when running the hrtimer queue in the softirq
 151  * @cb_pending:         list of timers where the callback is pending
 152  * @offset:             offset of this clock to the monotonic base
 153  * @reprogram:          function to reprogram the timer event
 154  */
 155 struct hrtimer_clock_base {
 156         struct hrtimer_cpu_base *cpu_base;
 157         clockid_t               index;
 158         struct rb_root          active;
 159         struct rb_node          *first;
 160         ktime_t                 resolution;
 161         ktime_t                 (*get_time)(void);
 162         ktime_t                 (*get_softirq_time)(void);
 163         ktime_t                 softirq_time;
 164 #ifdef CONFIG_HIGH_RES_TIMERS
 165         ktime_t                 offset;
 166         int                     (*reprogram)(struct hrtimer *t,
 167                                              struct hrtimer_clock_base *b,
 168                                              ktime_t n);
 169 #endif
 170 };
 171
 172 #define HRTIMER_MAX_CLOCK_BASES 2
 173
 174 /*
 175  * struct hrtimer_cpu_base - the per cpu clock bases
 176  * @lock:               lock protecting the base and associated clock bases
 177  *                      and timers
 178  * @lock_key:           the lock_class_key for use with lockdep
 179  * @clock_base:         array of clock bases for this cpu
 180  * @curr_timer:         the timer which is executing a callback right now
 181  * @expires_next:       absolute time of the next event which was scheduled
 182  *                      via clock_set_next_event()
 183  * @hres_active:        State of high resolution mode
 184  * @check_clocks:       Indictator, when set evaluate time source and clock
 185  *                      event devices whether high resolution mode can be
 186  *                      activated.
 187  * @cb_pending:         Expired timers are moved from the rbtree to this
 188  *                      list in the timer interrupt. The list is processed
 189  *                      in the softirq.
 190  * @nr_events:          Total number of timer interrupt events
 191  */
 192 struct hrtimer_cpu_base {
 193         spinlock_t                      lock;
 194         struct lock_class_key           lock_key;
 195         struct hrtimer_clock_base       clock_base[HRTIMER_MAX_CLOCK_BASES];
 196 #ifdef CONFIG_HIGH_RES_TIMERS
 197         ktime_t                         expires_next;
 198         int                             hres_active;
 199         struct list_head                cb_pending;
 200         unsigned long                   nr_events;
 201 #endif
 202 };
 203
 204 #ifdef CONFIG_HIGH_RES_TIMERS
 205 struct clock_event_device;
 206
 207 extern void clock_was_set(void);
 208 extern void hrtimer_interrupt(struct clock_event_device *dev);
 209
 210 /*
 211  * In high resolution mode the time reference must be read accurate
 212  */
 213 static inline ktime_t hrtimer_cb_get_time(struct hrtimer *timer)
 214 {
 215         return timer->base->get_time();
 216 }
 217
 218 /*
 219  * The resolution of the clocks. The resolution value is returned in
 220  * the clock_getres() system call to give application programmers an
 221  * idea of the (in)accuracy of timers. Timer values are rounded up to
 222  * this resolution values.
 223  */
 224 # define KTIME_HIGH_RES         (ktime_t) { .tv64 = 1 }
 225 # define KTIME_MONOTONIC_RES    KTIME_HIGH_RES
 226
 227 #else
 228
 229 # define KTIME_MONOTONIC_RES    KTIME_LOW_RES
 230
 231 /*
 232  * clock_was_set() is a NOP for non- high-resolution systems. The
 233  * time-sorted order guarantees that a timer does not expire early and
 234  * is expired in the next softirq when the clock was advanced.
 235  */
 236 static inline void clock_was_set(void) { }
 237
 238 /*
 239  * In non high resolution mode the time reference is taken from
 240  * the base softirq time variable.
 241  */
 242 static inline ktime_t hrtimer_cb_get_time(struct hrtimer *timer)
 243 {
 244         return timer->base->softirq_time;
 245 }
 246
 247 #endif
 248
 249 extern ktime_t ktime_get(void);
 250 extern ktime_t ktime_get_real(void);
 251
 252 /* Exported timer functions: */
 253
 254 /* Initialize timers: */
 255 extern void hrtimer_init(struct hrtimer *timer, clockid_t which_clock,
 256                          enum hrtimer_mode mode);
 257
 258 /* Basic timer operations: */
 259 extern int hrtimer_start(struct hrtimer *timer, ktime_t tim,
 260                          const enum hrtimer_mode mode);
 261 extern int hrtimer_cancel(struct hrtimer *timer);
 262 extern int hrtimer_try_to_cancel(struct hrtimer *timer);
 263
 264 static inline int hrtimer_restart(struct hrtimer *timer)
 265 {
 266         return hrtimer_start(timer, timer->expires, HRTIMER_MODE_ABS);
 267 }
 268
 269 /* Query timers: */
 270 extern ktime_t hrtimer_get_remaining(const struct hrtimer *timer);
 271 extern int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp);
 272
 273 extern ktime_t hrtimer_get_next_event(void);
 274
 275 /*
 276  * A timer is active, when it is enqueued into the rbtree or the callback
 277  * function is running.
 278  */
 279 static inline int hrtimer_active(const struct hrtimer *timer)
 280 {
 281         return timer->state != HRTIMER_STATE_INACTIVE;
 282 }
 283
 284 /*
 285  * Helper function to check, whether the timer is on one of the queues
 286  */
 287 static inline int hrtimer_is_queued(struct hrtimer *timer)
 288 {
 289         return timer->state &
 290                 (HRTIMER_STATE_ENQUEUED | HRTIMER_STATE_PENDING);
 291 }
 292
 293 /* Forward a hrtimer so it expires after now: */
 294 extern unsigned long
 295 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval);
 296
 297 /* Precise sleep: */
 298 extern long hrtimer_nanosleep(struct timespec *rqtp,
 299                               struct timespec __user *rmtp,
 300                               const enum hrtimer_mode mode,
 301                               const clockid_t clockid);
 302 extern long hrtimer_nanosleep_restart(struct restart_block *restart_block);
 303
 304 extern void hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
 305                                  struct task_struct *tsk);
 306
 307 /* Soft interrupt function to run the hrtimer queues: */
 308 extern void hrtimer_run_queues(void);
 309
 310 /* Bootup initialization: */
 311 extern void __init hrtimers_init(void);
 312
 313 #if BITS_PER_LONG < 64
 314 extern unsigned long ktime_divns(const ktime_t kt, s64 div);
 315 #else /* BITS_PER_LONG < 64 */
 316 # define ktime_divns(kt, div)           (unsigned long)((kt).tv64 / (div))
 317 #endif
 318
 319 /*
 320  * Timer-statistics info:
 321  */
 322 #ifdef CONFIG_TIMER_STATS
 323
 324 extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
 325                                      void *timerf, char * comm);
 326
 327 static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
 328 {
 329         timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
 330                                  timer->function, timer->start_comm);
 331 }
 332
 333 extern void __timer_stats_hrtimer_set_start_info(struct hrtimer *timer,
 334                                                  void *addr);
 335
 336 static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
 337 {
 338         __timer_stats_hrtimer_set_start_info(timer, __builtin_return_address(0));
 339 }
 340
 341 static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
 342 {
 343         timer->start_site = NULL;
 344 }
 345 #else
 346 static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
 347 {
 348 }
 349
 350 static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
 351 {
 352 }
 353
 354 static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
 355 {
 356 }
 357 #endif
 358
 359 #endif