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
9 * $ gcc raw_skew.c -o raw_skew -lrt
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.
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.
26 #include <sys/timex.h>
29 #include "../kselftest.h"
31 static inline int ksft_exit_pass(void)
35 static inline int ksft_exit_fail(void)
42 #define CLOCK_MONOTONIC_RAW 4
43 #define NSEC_PER_SEC 1000000000LL
45 #define shift_right(x, s) ({ \
46 __typeof__(x) __x = (x); \
47 __typeof__(s) __s = (s); \
48 __x < 0 ? -(-__x >> __s) : __x >> __s; \
51 long long llabs(long long val)
58 unsigned long long ts_to_nsec(struct timespec ts)
60 return ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec;
63 struct timespec nsec_to_ts(long long ns)
67 ts.tv_sec = ns/NSEC_PER_SEC;
68 ts.tv_nsec = ns%NSEC_PER_SEC;
72 long long diff_timespec(struct timespec start, struct timespec end)
74 long long start_ns, end_ns;
76 start_ns = ts_to_nsec(start);
77 end_ns = ts_to_nsec(end);
78 return end_ns - start_ns;
81 void get_monotonic_and_raw(struct timespec *mon, struct timespec *raw)
83 struct timespec start, mid, end;
84 long long diff = 0, tmp;
87 for (i = 0; i < 3; i++) {
90 clock_gettime(CLOCK_MONOTONIC, &start);
91 clock_gettime(CLOCK_MONOTONIC_RAW, &mid);
92 clock_gettime(CLOCK_MONOTONIC, &end);
94 newdiff = diff_timespec(start, end);
95 if (diff == 0 || newdiff < diff) {
98 tmp = (ts_to_nsec(start) + ts_to_nsec(end))/2;
99 *mon = nsec_to_ts(tmp);
104 int main(int argv, char **argc)
106 struct timespec mon, raw, start, end;
107 long long delta1, delta2, interval, eppm, ppm;
108 struct timex tx1, tx2;
110 setbuf(stdout, NULL);
112 if (clock_gettime(CLOCK_MONOTONIC_RAW, &raw)) {
113 printf("ERR: NO CLOCK_MONOTONIC_RAW\n");
119 get_monotonic_and_raw(&mon, &raw);
121 delta1 = diff_timespec(mon, raw);
124 printf("WARNING: ADJ_OFFSET in progress, this will cause inaccurate results\n");
126 printf("Estimating clock drift: ");
130 get_monotonic_and_raw(&mon, &raw);
134 delta2 = diff_timespec(mon, raw);
136 interval = diff_timespec(start, end);
138 /* calculate measured ppm between MONOTONIC and MONOTONIC_RAW */
139 eppm = ((delta2-delta1)*NSEC_PER_SEC)/interval;
141 printf("%lld.%i(est)", eppm/1000, abs((int)(eppm%1000)));
143 /* Avg the two actual freq samples adjtimex gave us */
144 ppm = (tx1.freq + tx2.freq) * 1000 / 2;
145 ppm = (long long)tx1.freq * 1000;
146 ppm = shift_right(ppm, 16);
147 printf(" %lld.%i(act)", ppm/1000, abs((int)(ppm%1000)));
149 if (llabs(eppm - ppm) > 1000) {
150 if (tx1.offset || tx2.offset ||
151 tx1.freq != tx2.freq || tx1.tick != tx2.tick) {
153 return ksft_exit_skip("The clock was adjusted externally. Shutdown NTPd or other time sync daemons\n");
155 printf(" [FAILED]\n");
156 return ksft_exit_fail();
159 return ksft_exit_pass();