osfmk/kern/timer.h

   1 /*
   2  * Copyright (c) 2000-2007 Apple Inc. All rights reserved.
   3  *
   4  * @APPLE_OSREFERENCE_LICENSE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
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   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License. The rights granted to you under the License
  10  * may not be used to create, or enable the creation or redistribution of,
  11  * unlawful or unlicensed copies of an Apple operating system, or to
  12  * circumvent, violate, or enable the circumvention or violation of, any
  13  * terms of an Apple operating system software license agreement.
  14  *
  15  * Please obtain a copy of the License at
  16  * http://www.opensource.apple.com/apsl/ and read it before using this file.
  17  *
  18  * The Original Code and all software distributed under the License are
  19  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  20  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  21  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  22  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  23  * Please see the License for the specific language governing rights and
  24  * limitations under the License.
  25  *
  26  * @APPLE_OSREFERENCE_LICENSE_HEADER_END@
  27  */
  28 /*
  29  * @OSF_COPYRIGHT@
  30  */
  31 /*
  32  * Mach Operating System
  33  * Copyright (c) 1991,1990,1989,1988,1987 Carnegie Mellon University
  34  * All Rights Reserved.
  35  *
  36  * Permission to use, copy, modify and distribute this software and its
  37  * documentation is hereby granted, provided that both the copyright
  38  * notice and this permission notice appear in all copies of the
  39  * software, derivative works or modified versions, and any portions
  40  * thereof, and that both notices appear in supporting documentation.
  41  *
  42  * CARNEGIE MELLON ALLOWS FREE USE OF THIS SOFTWARE IN ITS "AS IS"
  43  * CONDITION.  CARNEGIE MELLON DISCLAIMS ANY LIABILITY OF ANY KIND FOR
  44  * ANY DAMAGES WHATSOEVER RESULTING FROM THE USE OF THIS SOFTWARE.
  45  *
  46  * Carnegie Mellon requests users of this software to return to
  47  *
  48  *  Software Distribution Coordinator  or  Software.Distribution@CS.CMU.EDU
  49  *  School of Computer Science
  50  *  Carnegie Mellon University
  51  *  Pittsburgh PA 15213-3890
  52  *
  53  * any improvements or extensions that they make and grant Carnegie Mellon
  54  * the rights to redistribute these changes.
  55  */
  56 /*
  57  */
  58
  59 #ifndef _KERN_TIMER_H_
  60 #define _KERN_TIMER_H_
  61
  62 #include <kern/kern_types.h>
  63
  64 /*
  65  * Some platforms have very expensive timebase routines. An optimization
  66  * is to avoid switching timers on kernel exit/entry, which results in all
  67  * time billed to the system timer. However, when exposed to userspace,
  68  * we report as user time to indicate that work was done on behalf of
  69  * userspace.
  70  *
  71  * Although this policy is implemented as a global variable, we snapshot it
  72  * at key points in the thread structure (when the thread is locked and
  73  * executing in the kernel) to avoid imbalances.
  74  */
  75 extern int precise_user_kernel_time;
  76
  77 /*
  78  * thread must be locked, or be the current executing thread, so that
  79  * it doesn't transition from user to kernel while updating the
  80  * thread-local value (or in kernel debugger context). In the future,
  81  * we make take into account task-level or thread-level policy.
  82  */
  83 #define use_precise_user_kernel_time(thread) (precise_user_kernel_time)
  84
  85 /*
  86  * Definitions for high resolution timers.
  87  */
  88
  89 struct timer {
  90         uint64_t tstamp;
  91 #if defined(__LP64__)
  92         uint64_t all_bits;
  93 #else /* defined(__LP64__) */
  94         /* A check word on the high portion allows atomic updates. */
  95         uint32_t low_bits;
  96         uint32_t high_bits;
  97         uint32_t high_bits_check;
  98 #endif /* !defined(__LP64__) */
  99 };
 100
 101 typedef struct timer timer_data_t, *timer_t;
 102
 103 /*
 104  * Initialize the `timer`.
 105  */
 106 void timer_init(timer_t timer);
 107
 108 /*
 109  * Start the `timer` at time `tstamp`.
 110  */
 111 void timer_start(timer_t timer, uint64_t tstamp);
 112
 113 /*
 114  * Stop the `timer` and update it with time `tstamp`.
 115  */
 116 void timer_stop(timer_t timer, uint64_t tstamp);
 117
 118 /*
 119  * Update the `timer` at time `tstamp`, leaving it running.
 120  */
 121 void timer_update(timer_t timer, uint64_t tstamp);
 122
 123 /*
 124  * Update the `timer` with time `tstamp` and start `new_timer`.
 125  */
 126 void timer_switch(timer_t timer, uint64_t tstamp, timer_t new_timer);
 127
 128 /*
 129  * Update the thread timer at an "event," like a context switch, at time
 130  * `tstamp`.  This stops the current timer and starts the `new_timer` running.
 131  *
 132  * Must be called with interrupts disabled.
 133  */
 134 void processor_timer_switch_thread(uint64_t tstamp, timer_t new_timer);
 135
 136 /*
 137  * Return the difference between the `timer` and a previous value pointed to by
 138  * `prev_in_cur_out`.  Store the current value of the timer to
 139  * `prev_in_cur_out`.
 140  */
 141 uint64_t timer_delta(timer_t timer, uint64_t *prev_in_cur_out);
 142
 143 /*
 144  * Read the accumulated time of `timer`.
 145  */
 146 #if defined(__LP64__)
 147 static inline
 148 uint64_t
 149 timer_grab(timer_t timer)
 150 {
 151         return timer->all_bits;
 152 }
 153 #else /* defined(__LP64__) */
 154 uint64_t timer_grab(timer_t timer);
 155 #endif /* !defined(__LP64__) */
 156
 157 #endif /* _KERN_TIMER_H_ */