aboutsummaryrefslogtreecommitdiffstats
path: root/include/linux/hrtimer.h
blob: 5bdbc744e773096dbcbdd49d12a81afe90beaa90 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
/*
 *  include/linux/hrtimer.h
 *
 *  hrtimers - High-resolution kernel timers
 *
 *   Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
 *   Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
 *
 *  data type definitions, declarations, prototypes
 *
 *  Started by: Thomas Gleixner and Ingo Molnar
 *
 *  For licencing details see kernel-base/COPYING
 */
#ifndef _LINUX_HRTIMER_H
#define _LINUX_HRTIMER_H

#include <linux/rbtree.h>
#include <linux/ktime.h>
#include <linux/init.h>
#include <linux/list.h>
#include <linux/wait.h>

struct hrtimer_clock_base;
struct hrtimer_cpu_base;

/*
 * Mode arguments of xxx_hrtimer functions:
 */
enum hrtimer_mode {
	HRTIMER_MODE_ABS,	/* Time value is absolute */
	HRTIMER_MODE_REL,	/* Time value is relative to now */
};

/*
 * Return values for the callback function
 */
enum hrtimer_restart {
	HRTIMER_NORESTART,	/* Timer is not restarted */
	HRTIMER_RESTART,	/* Timer must be restarted */
};

/*
 * hrtimer callback modes:
 *
 *	HRTIMER_CB_SOFTIRQ:		Callback must run in softirq context
 *	HRTIMER_CB_IRQSAFE:		Callback may run in hardirq context
 *	HRTIMER_CB_IRQSAFE_NO_RESTART:	Callback may run in hardirq context and
 *					does not restart the timer
 *	HRTIMER_CB_IRQSAFE_NO_SOFTIRQ:	Callback must run in hardirq context
 *					Special mode for tick emultation
 */
enum hrtimer_cb_mode {
	HRTIMER_CB_SOFTIRQ,
	HRTIMER_CB_IRQSAFE,
	HRTIMER_CB_IRQSAFE_NO_RESTART,
	HRTIMER_CB_IRQSAFE_NO_SOFTIRQ,
};

/*
 * Values to track state of the timer
 *
 * Possible states:
 *
 * 0x00		inactive
 * 0x01		enqueued into rbtree
 * 0x02		callback function running
 * 0x04		callback pending (high resolution mode)
 *
 * Special case:
 * 0x03		callback function running and enqueued
 *		(was requeued on another CPU)
 * The "callback function running and enqueued" status is only possible on
 * SMP. It happens for example when a posix timer expired and the callback
 * queued a signal. Between dropping the lock which protects the posix timer
 * and reacquiring the base lock of the hrtimer, another CPU can deliver the
 * signal and rearm the timer. We have to preserve the callback running state,
 * as otherwise the timer could be removed before the softirq code finishes the
 * the handling of the timer.
 *
 * The HRTIMER_STATE_ENQUEUE bit is always or'ed to the current state to
 * preserve the HRTIMER_STATE_CALLBACK bit in the above scenario.
 *
 * All state transitions are protected by cpu_base->lock.
 */
#define HRTIMER_STATE_INACTIVE	0x00
#define HRTIMER_STATE_ENQUEUED	0x01
#define HRTIMER_STATE_CALLBACK	0x02
#define HRTIMER_STATE_PENDING	0x04

/**
 * struct hrtimer - the basic hrtimer structure
 * @node:	red black tree node for time ordered insertion
 * @expires:	the absolute expiry time in the hrtimers internal
 *		representation. The time is related to the clock on
 *		which the timer is based.
 * @function:	timer expiry callback function
 * @base:	pointer to the timer base (per cpu and per clock)
 * @state:	state information (See bit values above)
 * @cb_mode:	high resolution timer feature to select the callback execution
 *		 mode
 * @cb_entry:	list head to enqueue an expired timer into the callback list
 * @start_site:	timer statistics field to store the site where the timer
 *		was started
 * @start_comm: timer statistics field to store the name of the process which
 *		started the timer
 * @start_pid: timer statistics field to store the pid of the task which
 *		started the timer
 *
 * The hrtimer structure must be initialized by hrtimer_init()
 */
struct hrtimer {
	struct rb_node			node;
	ktime_t				expires;
	enum hrtimer_restart		(*function)(struct hrtimer *);
	struct hrtimer_clock_base	*base;
	unsigned long			state;
#ifdef CONFIG_HIGH_RES_TIMERS
	enum hrtimer_cb_mode		cb_mode;
	struct list_head		cb_entry;
#endif
#ifdef CONFIG_TIMER_STATS
	void				*start_site;
	char				start_comm[16];
	int				start_pid;
#endif
};

/**
 * struct hrtimer_sleeper - simple sleeper structure
 * @timer:	embedded timer structure
 * @task:	task to wake up
 *
 * task is set to NULL, when the timer expires.
 */
struct hrtimer_sleeper {
	struct hrtimer timer;
	struct task_struct *task;
};

/**
 * struct hrtimer_clock_base - the timer base for a specific clock
 * @cpu_base:		per cpu clock base
 * @index:		clock type index for per_cpu support when moving a
 *			timer to a base on another cpu.
 * @active:		red black tree root node for the active timers
 * @first:		pointer to the timer node which expires first
 * @resolution:		the resolution of the clock, in nanoseconds
 * @get_time:		function to retrieve the current time of the clock
 * @get_softirq_time:	function to retrieve the current time from the softirq
 * @softirq_time:	the time when running the hrtimer queue in the softirq
 * @cb_pending:		list of timers where the callback is pending
 * @offset:		offset of this clock to the monotonic base
 * @reprogram:		function to reprogram the timer event
 */
struct hrtimer_clock_base {
	struct hrtimer_cpu_base	*cpu_base;
	clockid_t		index;
	struct rb_root		active;
	struct rb_node		*first;
	ktime_t			resolution;
	ktime_t			(*get_time)(void);
	ktime_t			(*get_softirq_time)(void);
	ktime_t			softirq_time;
#ifdef CONFIG_HIGH_RES_TIMERS
	ktime_t			offset;
	int			(*reprogram)(struct hrtimer *t,
					     struct hrtimer_clock_base *b,
					     ktime_t n);
#endif
};

#define HRTIMER_MAX_CLOCK_BASES 2

/*
 * struct hrtimer_cpu_base - the per cpu clock bases
 * @lock:		lock protecting the base and associated clock bases
 *			and timers
 * @lock_key:		the lock_class_key for use with lockdep
 * @clock_base:		array of clock bases for this cpu
 * @curr_timer:		the timer which is executing a callback right now
 * @expires_next:	absolute time of the next event which was scheduled
 *			via clock_set_next_event()
 * @hres_active:	State of high resolution mode
 * @check_clocks:	Indictator, when set evaluate time source and clock
 *			event devices whether high resolution mode can be
 *			activated.
 * @cb_pending:		Expired timers are moved from the rbtree to this
 *			list in the timer interrupt. The list is processed
 *			in the softirq.
 * @nr_events:		Total number of timer interrupt events
 */
struct hrtimer_cpu_base {
	spinlock_t			lock;
	struct lock_class_key		lock_key;
	struct hrtimer_clock_base	clock_base[HRTIMER_MAX_CLOCK_BASES];
#ifdef CONFIG_HIGH_RES_TIMERS
	ktime_t				expires_next;
	int				hres_active;
	struct list_head		cb_pending;
	unsigned long			nr_events;
#endif
};

#ifdef CONFIG_HIGH_RES_TIMERS
struct clock_event_device;

extern void clock_was_set(void);
extern void hrtimer_interrupt(struct clock_event_device *dev);

/*
 * In high resolution mode the time reference must be read accurate
 */
static inline ktime_t hrtimer_cb_get_time(struct hrtimer *timer)
{
	return timer->base->get_time();
}

/*
 * The resolution of the clocks. The resolution value is returned in
 * the clock_getres() system call to give application programmers an
 * idea of the (in)accuracy of timers. Timer values are rounded up to
 * this resolution values.
 */
# define KTIME_HIGH_RES		(ktime_t) { .tv64 = 1 }
# define KTIME_MONOTONIC_RES	KTIME_HIGH_RES

#else

# define KTIME_MONOTONIC_RES	KTIME_LOW_RES

/*
 * clock_was_set() is a NOP for non- high-resolution systems. The
 * time-sorted order guarantees that a timer does not expire early and
 * is expired in the next softirq when the clock was advanced.
 */
static inline void clock_was_set(void) { }

/*
 * In non high resolution mode the time reference is taken from
 * the base softirq time variable.
 */
static inline ktime_t hrtimer_cb_get_time(struct hrtimer *timer)
{
	return timer->base->softirq_time;
}

#endif

extern ktime_t ktime_get(void);
extern ktime_t ktime_get_real(void);

/* Exported timer functions: */

/* Initialize timers: */
extern void hrtimer_init(struct hrtimer *timer, clockid_t which_clock,
			 enum hrtimer_mode mode);

/* Basic timer operations: */
extern int hrtimer_start(struct hrtimer *timer, ktime_t tim,
			 const enum hrtimer_mode mode);
extern int hrtimer_cancel(struct hrtimer *timer);
extern int hrtimer_try_to_cancel(struct hrtimer *timer);

static inline int hrtimer_restart(struct hrtimer *timer)
{
	return hrtimer_start(timer, timer->expires, HRTIMER_MODE_ABS);
}

/* Query timers: */
extern ktime_t hrtimer_get_remaining(const struct hrtimer *timer);
extern int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp);

extern ktime_t hrtimer_get_next_event(void);

/*
 * A timer is active, when it is enqueued into the rbtree or the callback
 * function is running.
 */
static inline int hrtimer_active(const struct hrtimer *timer)
{
	return timer->state != HRTIMER_STATE_INACTIVE;
}

/*
 * Helper function to check, whether the timer is on one of the queues
 */
static inline int hrtimer_is_queued(struct hrtimer *timer)
{
	return timer->state &
		(HRTIMER_STATE_ENQUEUED | HRTIMER_STATE_PENDING);
}

/* Forward a hrtimer so it expires after now: */
extern unsigned long
hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval);

/* Precise sleep: */
extern long hrtimer_nanosleep(struct timespec *rqtp,
			      struct timespec __user *rmtp,
			      const enum hrtimer_mode mode,
			      const clockid_t clockid);
extern long hrtimer_nanosleep_restart(struct restart_block *restart_block);

extern void hrtimer_init_sleeper(struct hrtimer_sleeper *sl,
				 struct task_struct *tsk);

/* Soft interrupt function to run the hrtimer queues: */
extern void hrtimer_run_queues(void);

/* Bootup initialization: */
extern void __init hrtimers_init(void);

#if BITS_PER_LONG < 64
extern unsigned long ktime_divns(const ktime_t kt, s64 div);
#else /* BITS_PER_LONG < 64 */
# define ktime_divns(kt, div)		(unsigned long)((kt).tv64 / (div))
#endif

/* Show pending timers: */
extern void sysrq_timer_list_show(void);

/*
 * Timer-statistics info:
 */
#ifdef CONFIG_TIMER_STATS

extern void timer_stats_update_stats(void *timer, pid_t pid, void *startf,
				     void *timerf, char * comm);

static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
{
	timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
				 timer->function, timer->start_comm);
}

extern void __timer_stats_hrtimer_set_start_info(struct hrtimer *timer,
						 void *addr);

static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
{
	__timer_stats_hrtimer_set_start_info(timer, __builtin_return_address(0));
}

static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
{
	timer->start_site = NULL;
}
#else
static inline void timer_stats_account_hrtimer(struct hrtimer *timer)
{
}

static inline void timer_stats_hrtimer_set_start_info(struct hrtimer *timer)
{
}

static inline void timer_stats_hrtimer_clear_start_info(struct hrtimer *timer)
{
}
#endif

#endif