tools/testing/selftests/timers/leapcrash.c

   1 /* Demo leapsecond deadlock
   2  *              by: John Stultz (john.stultz@linaro.org)
   3  *              (C) Copyright IBM 2012
   4  *              (C) Copyright 2013, 2015 Linaro Limited
   5  *              Licensed under the GPL
   6  *
   7  * This test demonstrates leapsecond deadlock that is possibe
   8  * on kernels from 2.6.26 to 3.3.
   9  *
  10  * WARNING: THIS WILL LIKELY HARDHANG SYSTEMS AND MAY LOSE DATA
  11  * RUN AT YOUR OWN RISK!
  12  *  To build:
  13  *      $ gcc leapcrash.c -o leapcrash -lrt
  14  */
  15
  16
  17
  18 #include <stdio.h>
  19 #include <stdlib.h>
  20 #include <time.h>
  21 #include <sys/time.h>
  22 #include <sys/timex.h>
  23 #include <string.h>
  24 #include <signal.h>
  25 #include "../kselftest.h"
  26
  27 /* clear NTP time_status & time_state */
  28 int clear_time_state(void)
  29 {
  30         struct timex tx;
  31         int ret;
  32
  33         /*
  34          * We have to call adjtime twice here, as kernels
  35          * prior to 6b1859dba01c7 (included in 3.5 and
  36          * -stable), had an issue with the state machine
  37          * and wouldn't clear the STA_INS/DEL flag directly.
  38          */
  39         tx.modes = ADJ_STATUS;
  40         tx.status = STA_PLL;
  41         ret = adjtimex(&tx);
  42
  43         tx.modes = ADJ_STATUS;
  44         tx.status = 0;
  45         ret = adjtimex(&tx);
  46
  47         return ret;
  48 }
  49
  50 /* Make sure we cleanup on ctrl-c */
  51 void handler(int unused)
  52 {
  53         clear_time_state();
  54         exit(0);
  55 }
  56
  57
  58 int main(void)
  59 {
  60         struct timex tx;
  61         struct timespec ts;
  62         time_t next_leap;
  63         int count = 0;
  64
  65         setbuf(stdout, NULL);
  66
  67         signal(SIGINT, handler);
  68         signal(SIGKILL, handler);
  69         printf("This runs for a few minutes. Press ctrl-c to stop\n");
  70
  71         clear_time_state();
  72
  73
  74         /* Get the current time */
  75         clock_gettime(CLOCK_REALTIME, &ts);
  76
  77         /* Calculate the next possible leap second 23:59:60 GMT */
  78         next_leap = ts.tv_sec;
  79         next_leap += 86400 - (next_leap % 86400);
  80
  81         for (count = 0; count < 20; count++) {
  82                 struct timeval tv;
  83
  84
  85                 /* set the time to 2 seconds before the leap */
  86                 tv.tv_sec = next_leap - 2;
  87                 tv.tv_usec = 0;
  88                 if (settimeofday(&tv, NULL)) {
  89                         printf("Error: You're likely not running with proper (ie: root) permissions\n");
  90                         return ksft_exit_fail();
  91                 }
  92                 tx.modes = 0;
  93                 adjtimex(&tx);
  94
  95                 /* hammer on adjtime w/ STA_INS */
  96                 while (tx.time.tv_sec < next_leap + 1) {
  97                         /* Set the leap second insert flag */
  98                         tx.modes = ADJ_STATUS;
  99                         tx.status = STA_INS;
 100                         adjtimex(&tx);
 101                 }
 102                 clear_time_state();
 103                 printf(".");
 104         }
 105         printf("[OK]\n");
 106         return ksft_exit_pass();
 107 }