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
  7   * as defined in and that are subject to the Apple Public Source License
  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  #if __LP64__
 90  #define TIMER_ALIGNMENT
 91  #else
 92  #define TIMER_ALIGNMENT __attribute__((packed, aligned(4)))
 93  #endif
 94  
 95  struct timer {
 96  	uint64_t tstamp;
 97  #if defined(__LP64__)
 98  	uint64_t all_bits;
 99  #else /* defined(__LP64__) */
100  	/* A check word on the high portion allows atomic updates. */
101  	uint32_t low_bits;
102  	uint32_t high_bits;
103  	uint32_t high_bits_check;
104  #endif /* !defined(__LP64__) */
105  } TIMER_ALIGNMENT;
106  
107  typedef struct timer timer_data_t, *timer_t;
108  
109  /*
110   * Initialize the `timer`.
111   */
112  void timer_init(timer_t timer);
113  
114  /*
115   * Start the `timer` at time `tstamp`.
116   */
117  void timer_start(timer_t timer, uint64_t tstamp);
118  
119  /*
120   * Stop the `timer` and update it with time `tstamp`.
121   */
122  void timer_stop(timer_t timer, uint64_t tstamp);
123  
124  /*
125   * Update the `timer` at time `tstamp`, leaving it running.
126   */
127  void timer_update(timer_t timer, uint64_t tstamp);
128  
129  /*
130   * Update the `timer` with time `tstamp` and start `new_timer`.
131   */
132  void timer_switch(timer_t timer, uint64_t tstamp, timer_t new_timer);
133  
134  /*
135   * Update the thread timer at an "event," like a context switch, at time
136   * `tstamp`.  This stops the current timer and starts the `new_timer` running.
137   *
138   * Must be called with interrupts disabled.
139   */
140  void processor_timer_switch_thread(uint64_t tstamp, timer_t new_timer);
141  
142  /*
143   * Return the difference between the `timer` and a previous value pointed to by
144   * `prev_in_cur_out`.  Store the current value of the timer to
145   * `prev_in_cur_out`.
146   */
147  uint64_t timer_delta(timer_t timer, uint64_t *prev_in_cur_out);
148  
149  /*
150   * Read the accumulated time of `timer`.
151   */
152  #if defined(__LP64__)
153  static inline
154  uint64_t
155  timer_grab(timer_t timer)
156  {
157  	return timer->all_bits;
158  }
159  #else /* defined(__LP64__) */
160  uint64_t timer_grab(timer_t timer);
161  #endif /* !defined(__LP64__) */
162  
163  #endif /* _KERN_TIMER_H_ */