1 /* CLOCK_MONOTONIC vs CLOCK_MONOTONIC_RAW skew test
2 * by: john stultz (johnstul@us.ibm.com)
3 * John Stultz <john.stultz@linaro.org>
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 "../kselftest.h"
29
30 #define CLOCK_MONOTONIC_RAW 4
31 #define NSEC_PER_SEC 1000000000LL
32
33 #define shift_right(x, s) ({ \
34 __typeof__(x) __x = (x); \
35 __typeof__(s) __s = (s); \
36 __x < 0 ? -(-__x >> __s) : __x >> __s; \
37 })
38
llabs(long long val)39 long long llabs(long long val)
40 {
41 if (val < 0)
42 val = -val;
43 return val;
44 }
45
ts_to_nsec(struct timespec ts)46 unsigned long long ts_to_nsec(struct timespec ts)
47 {
48 return ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
49 }
50
nsec_to_ts(long long ns)51 struct timespec nsec_to_ts(long long ns)
52 {
53 struct timespec ts;
54
55 ts.tv_sec = ns/NSEC_PER_SEC;
56 ts.tv_nsec = ns%NSEC_PER_SEC;
57 return ts;
58 }
59
diff_timespec(struct timespec start,struct timespec end)60 long long diff_timespec(struct timespec start, struct timespec end)
61 {
62 long long start_ns, end_ns;
63
64 start_ns = ts_to_nsec(start);
65 end_ns = ts_to_nsec(end);
66 return end_ns - start_ns;
67 }
68
get_monotonic_and_raw(struct timespec * mon,struct timespec * raw)69 void get_monotonic_and_raw(struct timespec *mon, struct timespec *raw)
70 {
71 struct timespec start, mid, end;
72 long long diff = 0, tmp;
73 int i;
74
75 for (i = 0; i < 3; i++) {
76 long long newdiff;
77
78 clock_gettime(CLOCK_MONOTONIC, &start);
79 clock_gettime(CLOCK_MONOTONIC_RAW, &mid);
80 clock_gettime(CLOCK_MONOTONIC, &end);
81
82 newdiff = diff_timespec(start, end);
83 if (diff == 0 || newdiff < diff) {
84 diff = newdiff;
85 *raw = mid;
86 tmp = (ts_to_nsec(start) + ts_to_nsec(end))/2;
87 *mon = nsec_to_ts(tmp);
88 }
89 }
90 }
91
main(int argv,char ** argc)92 int main(int argv, char **argc)
93 {
94 struct timespec mon, raw, start, end;
95 long long delta1, delta2, interval, eppm, ppm;
96 struct timex tx1, tx2;
97
98 setbuf(stdout, NULL);
99
100 if (clock_gettime(CLOCK_MONOTONIC_RAW, &raw)) {
101 printf("ERR: NO CLOCK_MONOTONIC_RAW\n");
102 return -1;
103 }
104
105 tx1.modes = 0;
106 adjtimex(&tx1);
107 get_monotonic_and_raw(&mon, &raw);
108 start = mon;
109 delta1 = diff_timespec(mon, raw);
110
111 if (tx1.offset)
112 printf("WARNING: ADJ_OFFSET in progress, this will cause inaccurate results\n");
113
114 printf("Estimating clock drift: ");
115 fflush(stdout);
116 sleep(120);
117
118 get_monotonic_and_raw(&mon, &raw);
119 end = mon;
120 tx2.modes = 0;
121 adjtimex(&tx2);
122 delta2 = diff_timespec(mon, raw);
123
124 interval = diff_timespec(start, end);
125
126 /* calculate measured ppm between MONOTONIC and MONOTONIC_RAW */
127 eppm = ((delta2-delta1)*NSEC_PER_SEC)/interval;
128 eppm = -eppm;
129 printf("%lld.%i(est)", eppm/1000, abs((int)(eppm%1000)));
130
131 /* Avg the two actual freq samples adjtimex gave us */
132 ppm = (tx1.freq + tx2.freq) * 1000 / 2;
133 ppm = (long long)tx1.freq * 1000;
134 ppm = shift_right(ppm, 16);
135 printf(" %lld.%i(act)", ppm/1000, abs((int)(ppm%1000)));
136
137 if (llabs(eppm - ppm) > 1000) {
138 if (tx1.offset || tx2.offset ||
139 tx1.freq != tx2.freq || tx1.tick != tx2.tick) {
140 printf(" [SKIP]\n");
141 return ksft_exit_skip("The clock was adjusted externally. Shutdown NTPd or other time sync daemons\n");
142 }
143 printf(" [FAILED]\n");
144 return ksft_exit_fail();
145 }
146 printf(" [OK]\n");
147 return ksft_exit_pass();
148 }
149