root/tools/testing/selftests/timers/raw_skew.c

DEFINITIONS

1. llabs
2. ts_to_nsec
3. nsec_to_ts
4. diff_timespec
5. get_monotonic_and_raw
6. main

   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 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 }