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 39 long long llabs(long long val) 40 { 41 if (val < 0) 42 val = -val; 43 return val; 44 } 45 46 unsigned long long ts_to_nsec(struct timespec ts) 47 { 48 return ts.tv_sec * NSEC_PER_SEC + ts.tv_nsec; 49 } 50 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 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 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 92 int main(int argc, char **argv) 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 = (long long)(tx1.freq + tx2.freq) * 1000 / 2; 133 ppm = shift_right(ppm, 16); 134 printf(" %lld.%i(act)", ppm/1000, abs((int)(ppm%1000))); 135 136 if (llabs(eppm - ppm) > 1000) { 137 if (tx1.offset || tx2.offset || 138 tx1.freq != tx2.freq || tx1.tick != tx2.tick) { 139 printf(" [SKIP]\n"); 140 return ksft_exit_skip("The clock was adjusted externally. Shutdown NTPd or other time sync daemons\n"); 141 } 142 printf(" [FAILED]\n"); 143 return ksft_exit_fail(); 144 } 145 printf(" [OK]\n"); 146 return ksft_exit_pass(); 147 } 148