Docs: Missing optional dependency on lttng-ust in README.md
[lttng-tools.git] / src / bin / lttng-sessiond / ust-clock.h
1 /*
2 * Copyright (C) 2010 Pierre-Marc Fournier
3 * Copyright (C) 2011 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
4 *
5 * This library is free software; you can redistribute it and/or
6 * modify it under the terms of the GNU Lesser General Public
7 * License as published by the Free Software Foundation; version 2.1 of
8 * the License.
9 *
10 * This library is distributed in the hope that it will be useful,
11 * but WITHOUT ANY WARRANTY; without even the implied warranty of
12 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 * Lesser General Public License for more details.
14 *
15 * You should have received a copy of the GNU Lesser General Public
16 * License along with this library; if not, write to the Free Software
17 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
18 */
19
20 #ifndef _UST_CLOCK_H
21 #define _UST_CLOCK_H
22
23 #include <time.h>
24 #include <sys/time.h>
25 #include <stdint.h>
26 #include <stddef.h>
27 #include <stdio.h>
28 #include <errno.h>
29
30 #include <common/compat/uuid.h>
31
32 /* TRACE CLOCK */
33
34 /*
35 * Currently using the kernel MONOTONIC clock, waiting for kernel-side
36 * LTTng to implement mmap'd trace clock.
37 */
38
39 /* Choosing correct trace clock */
40
41 static __inline__
42 uint64_t trace_clock_read64(void)
43 {
44 struct timespec ts;
45
46 clock_gettime(CLOCK_MONOTONIC, &ts);
47 return ((uint64_t) ts.tv_sec * 1000000000ULL) + ts.tv_nsec;
48 }
49
50 static __inline__
51 uint64_t trace_clock_freq(void)
52 {
53 return 1000000000ULL;
54 }
55
56 static __inline__
57 int trace_clock_uuid(char *uuid)
58 {
59 int ret = 0;
60 size_t len;
61 FILE *fp;
62
63 /*
64 * boot_id needs to be read once before being used concurrently
65 * to deal with a Linux kernel race. A fix is proposed for
66 * upstream, but the work-around is needed for older kernels.
67 */
68 fp = fopen("/proc/sys/kernel/random/boot_id", "r");
69 if (!fp) {
70 return -ENOENT;
71 }
72 len = fread(uuid, 1, UUID_STR_LEN - 1, fp);
73 if (len < UUID_STR_LEN - 1) {
74 ret = -EINVAL;
75 goto end;
76 }
77 uuid[UUID_STR_LEN - 1] = '\0';
78 end:
79 fclose(fp);
80 return ret;
81 }
82
83 #endif /* _UST_CLOCK_H */
This page took 0.030223 seconds and 4 git commands to generate.