1 /**************************************************************************
2 *
3 * Copyright 2008-2010 VMware, Inc.
4 * All Rights Reserved.
5 *
6 * Permission is hereby granted, free of charge, to any person obtaining a
7 * copy of this software and associated documentation files (the
8 * "Software"), to deal in the Software without restriction, including
9 * without limitation the rights to use, copy, modify, merge, publish,
10 * distribute, sub license, and/or sell copies of the Software, and to
11 * permit persons to whom the Software is furnished to do so, subject to
12 * the following conditions:
13 *
14 * The above copyright notice and this permission notice (including the
15 * next paragraph) shall be included in all copies or substantial portions
16 * of the Software.
17 *
18 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS
19 * OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
20 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT.
21 * IN NO EVENT SHALL VMWARE AND/OR ITS SUPPLIERS BE LIABLE FOR
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23 * TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE
24 * SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
25 *
26 **************************************************************************/
27
28 /**
29 * @file
30 * OS independent time-manipulation functions.
31 *
32 * @author Jose Fonseca <jfonseca@vmware.com>
33 */
34
35 #ifndef _OS_TIME_H_
36 #define _OS_TIME_H_
37
38 #include <stdbool.h>
39 #include <stdint.h>
40
41 #ifdef __cplusplus
42 extern "C" {
43 #endif
44
45 /* must be equal to PIPE_TIMEOUT_INFINITE */
46 #define OS_TIMEOUT_INFINITE 0xffffffffffffffffull
47
48 /*
49 * Get the current time in nanoseconds from an unknown base.
50 */
51 int64_t
52 os_time_get_nano(void);
53
54
55 /*
56 * Get the current time in microseconds from an unknown base.
57 */
58 static inline int64_t
os_time_get(void)59 os_time_get(void)
60 {
61 return os_time_get_nano() / 1000;
62 }
63
64
65 /*
66 * Sleep.
67 */
68 void
69 os_time_sleep(int64_t usecs);
70
71
72 /*
73 * Helper function for detecting time outs, taking in account overflow.
74 *
75 * Returns true if the current time has elapsed beyond the specified interval.
76 */
77 static inline bool
os_time_timeout(int64_t start,int64_t end,int64_t curr)78 os_time_timeout(int64_t start,
79 int64_t end,
80 int64_t curr)
81 {
82 if (start <= end)
83 return !(start <= curr && curr < end);
84 else
85 return !((start <= curr) || (curr < end));
86 }
87
88
89 /**
90 * Convert a relative timeout in nanoseconds into an absolute timeout,
91 * in other words, it returns current time + timeout.
92 * os_time_get_nano() must be monotonic.
93 * OS_TIMEOUT_INFINITE is passed through unchanged. If the calculation
94 * overflows, OS_TIMEOUT_INFINITE is returned.
95 */
96 int64_t
97 os_time_get_absolute_timeout(uint64_t timeout);
98
99
100 /**
101 * Wait until the variable at the given memory location is zero.
102 *
103 * \param var variable
104 * \param timeout timeout in ns, can be anything from 0 (no wait) to
105 * OS_TIMEOUT_INFINITE (wait forever)
106 * \return true if the variable is zero
107 */
108 bool
109 os_wait_until_zero(volatile int *var, uint64_t timeout);
110
111
112 /**
113 * Wait until the variable at the given memory location is zero.
114 * The timeout is the absolute time when the waiting should stop. If it is
115 * less than or equal to the current time, it only returns the status and
116 * doesn't wait. OS_TIMEOUT_INFINITE waits forever. This requires that
117 * os_time_get_nano is monotonic.
118 *
119 * \param var variable
120 * \param timeout the time in ns when the waiting should stop
121 * \return true if the variable is zero
122 */
123 bool
124 os_wait_until_zero_abs_timeout(volatile int *var, int64_t timeout);
125
126 #ifdef __cplusplus
127 }
128 #endif
129
130 #endif /* _OS_TIME_H_ */
131