xnu-3789.1.32.tar.gz

[apple/xnu.git] / osfmk / kern / timer.h

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/*
 * @OSF_COPYRIGHT@
 */
/* 
 * Mach Operating System
 * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
 * All Rights Reserved.
 * 
 * Permission to use, copy, modify and distribute this software and its
 * documentation is hereby granted, provided that both the copyright
 * notice and this permission notice appear in all copies of the
 * software, derivative works or modified versions, and any portions
 * thereof, and that both notices appear in supporting documentation.
 * 
 * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
 * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
 * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
 * 
 * Carnegie Mellon requests users of this software to return to
 * 
 *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
 *  School of Computer Science
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 *  Pittsburgh PA 15213-3890
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 * any improvements or extensions that they make and grant Carnegie Mellon
 * the rights to redistribute these changes.
 */
/*
 */

#ifndef	_KERN_TIMER_H_
#define _KERN_TIMER_H_

#include <kern/kern_types.h>

/*
 * Some platforms have very expensive timebase routines. An optimization
 * is to avoid switching timers on kernel exit/entry, which results in all
 * time billed to the system timer. However, when exposed to userspace,
 * we report as user time to indicate that work was done on behalf of
 * userspace.
 *
 * Although this policy is implemented as a global variable, we snapshot it
 * at key points in the thread structure (when the thread is locked and
 * executing in the kernel) to avoid imbalances.
 */
extern int precise_user_kernel_time;

/*
 * thread must be locked, or be the current executing thread, so that
 * it doesn't transition from user to kernel while updating the
 * thread-local value (or in kernel debugger context). In the future,
 * we make take into account task-level or thread-level policy.
 */
#define use_precise_user_kernel_time(thread) ( precise_user_kernel_time ) 

/*
 *	Definitions for high resolution timers.  A check
 *	word on the high portion allows atomic updates.
 */

struct timer {
	uint64_t	tstamp;
#if	defined(__LP64__)
	uint64_t	all_bits;
#else
	uint32_t	low_bits;
	uint32_t	high_bits;
	uint32_t	high_bits_check;
#endif
};

typedef struct timer	timer_data_t, *timer_t;

/*
 *	Exported kernel interface to timers
 */

/* Start a timer by setting the timestamp */
extern void		timer_start(
					timer_t		timer,
					uint64_t	tstamp);

/* Stop a timer by updating from the timestamp */
extern void		timer_stop(
					timer_t		timer,
					uint64_t	tstamp);

/* Update the timer and start a new one */
extern void		timer_switch(
					timer_t		timer,
					uint64_t	tstamp,
					timer_t		new_timer);

/* Update the thread timer at an event */
extern void		thread_timer_event(
					uint64_t	tstamp,
					timer_t		new_timer);

/* Initialize a timer */
extern void		timer_init(
					timer_t		timer);

/* Update a saved timer value and return delta to current value */
extern uint64_t	timer_delta(
					timer_t		timer,
					uint64_t	*save);

/* Advance a timer by a 64 bit value */
extern void		timer_advance(
					timer_t		timer,
					uint64_t	delta);

/*
 *	Exported hardware interface to timers
 */

/* Read timer value */
#if	defined(__LP64__)
static inline uint64_t timer_grab(
					timer_t		timer)
{
	return timer->all_bits;
}
#else
extern uint64_t	timer_grab(
					timer_t		timer);

/* Update timer value */
extern void		timer_update(
					timer_t		timer,
					uint32_t	new_high,
					uint32_t	new_low);
#endif	/* defined(__LP64__) */

#endif	/* _KERN_TIMER_H_ */