1 /* CLOCK_MONOTONIC vs CLOCK_MONOTONIC_RAW skew test
2 * by: john stultz ([email protected])
3 * John Stultz <[email protected]>
4 * (C) Copyright IBM 2012
5 * (C) Copyright Linaro Limited 2015
6 * Licensed under the GPLv2
7 *
8 * To build:
9 * $ gcc raw_skew.c -o raw_skew -lrt
10 *
11 * This program is free software: you can redistribute it and/or modify
12 * it under the terms of the GNU General Public License as published by
13 * the Free Software Foundation, either version 2 of the License, or
14 * (at your option) any later version.
15 *
16 * This program is distributed in the hope that it will be useful,
17 * but WITHOUT ANY WARRANTY; without even the implied warranty of
18 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19 * GNU General Public License for more details.
20 */
21
22 #include <stdio.h>
23 #include <unistd.h>
24 #include <stdlib.h>
25 #include <sys/time.h>
26 #include <sys/timex.h>
27 #include <time.h>
28 #include <include/vdso/time64.h>
29 #include "../kselftest.h"
30
31 #define shift_right(x, s) ({ \
32 __typeof__(x) __x = (x); \
33 __typeof__(s) __s = (s); \
34 __x < 0 ? -(-__x >> __s) : __x >> __s; \
35 })
36
llabs(long long val)37 long long llabs(long long val)
38 {
39 if (val < 0)
40 val = -val;
41 return val;
42 }
43
ts_to_nsec(struct timespec ts)44 unsigned long long ts_to_nsec(struct timespec ts)
45 {
46 return ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
47 }
48
nsec_to_ts(long long ns)49 struct timespec nsec_to_ts(long long ns)
50 {
51 struct timespec ts;
52
53 ts.tv_sec = ns/NSEC_PER_SEC;
54 ts.tv_nsec = ns%NSEC_PER_SEC;
55 return ts;
56 }
57
diff_timespec(struct timespec start,struct timespec end)58 long long diff_timespec(struct timespec start, struct timespec end)
59 {
60 long long start_ns, end_ns;
61
62 start_ns = ts_to_nsec(start);
63 end_ns = ts_to_nsec(end);
64 return end_ns - start_ns;
65 }
66
get_monotonic_and_raw(struct timespec * mon,struct timespec * raw)67 void get_monotonic_and_raw(struct timespec *mon, struct timespec *raw)
68 {
69 struct timespec start, mid, end;
70 long long diff = 0, tmp;
71 int i;
72
73 for (i = 0; i < 3; i++) {
74 long long newdiff;
75
76 clock_gettime(CLOCK_MONOTONIC, &start);
77 clock_gettime(CLOCK_MONOTONIC_RAW, &mid);
78 clock_gettime(CLOCK_MONOTONIC, &end);
79
80 newdiff = diff_timespec(start, end);
81 if (diff == 0 || newdiff < diff) {
82 diff = newdiff;
83 *raw = mid;
84 tmp = (ts_to_nsec(start) + ts_to_nsec(end))/2;
85 *mon = nsec_to_ts(tmp);
86 }
87 }
88 }
89
main(int argc,char ** argv)90 int main(int argc, char **argv)
91 {
92 struct timespec mon, raw, start, end;
93 long long delta1, delta2, interval, eppm, ppm;
94 struct timex tx1, tx2;
95
96 setbuf(stdout, NULL);
97
98 if (clock_gettime(CLOCK_MONOTONIC_RAW, &raw)) {
99 printf("ERR: NO CLOCK_MONOTONIC_RAW\n");
100 return -1;
101 }
102
103 tx1.modes = 0;
104 adjtimex(&tx1);
105 get_monotonic_and_raw(&mon, &raw);
106 start = mon;
107 delta1 = diff_timespec(mon, raw);
108
109 if (tx1.offset)
110 printf("WARNING: ADJ_OFFSET in progress, this will cause inaccurate results\n");
111
112 printf("Estimating clock drift: ");
113 fflush(stdout);
114 sleep(120);
115
116 get_monotonic_and_raw(&mon, &raw);
117 end = mon;
118 tx2.modes = 0;
119 adjtimex(&tx2);
120 delta2 = diff_timespec(mon, raw);
121
122 interval = diff_timespec(start, end);
123
124 /* calculate measured ppm between MONOTONIC and MONOTONIC_RAW */
125 eppm = ((delta2-delta1)*NSEC_PER_SEC)/interval;
126 eppm = -eppm;
127 printf("%lld.%i(est)", eppm/1000, abs((int)(eppm%1000)));
128
129 /* Avg the two actual freq samples adjtimex gave us */
130 ppm = (long long)(tx1.freq + tx2.freq) * 1000 / 2;
131 ppm = shift_right(ppm, 16);
132 printf(" %lld.%i(act)", ppm/1000, abs((int)(ppm%1000)));
133
134 if (llabs(eppm - ppm) > 1000) {
135 if (tx1.offset || tx2.offset ||
136 tx1.freq != tx2.freq || tx1.tick != tx2.tick) {
137 printf(" [SKIP]\n");
138 ksft_exit_skip("The clock was adjusted externally. Shutdown NTPd or other time sync daemons\n");
139 }
140 printf(" [FAILED]\n");
141 ksft_exit_fail();
142 }
143 printf(" [OK]\n");
144 ksft_exit_pass();
145 }
146