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 #ifdef KTEST
  26 #include "../kselftest.h"
  27 #else
  28 static inline int ksft_exit_pass(void)
  29 {
  30         exit(0);
  31 }
  32 static inline int ksft_exit_fail(void)
  33 {
  34         exit(1);
  35 }
  36 #endif
  37
  38
  39
  40 /* clear NTP time_status & time_state */
  41 int clear_time_state(void)
  42 {
  43         struct timex tx;
  44         int ret;
  45
  46         /*
  47          * We have to call adjtime twice here, as kernels
  48          * prior to 6b1859dba01c7 (included in 3.5 and
  49          * -stable), had an issue with the state machine
  50          * and wouldn't clear the STA_INS/DEL flag directly.
  51          */
  52         tx.modes = ADJ_STATUS;
  53         tx.status = STA_PLL;
  54         ret = adjtimex(&tx);
  55
  56         tx.modes = ADJ_STATUS;
  57         tx.status = 0;
  58         ret = adjtimex(&tx);
  59
  60         return ret;
  61 }
  62
  63 /* Make sure we cleanup on ctrl-c */
  64 void handler(int unused)
  65 {
  66         clear_time_state();
  67         exit(0);
  68 }
  69
  70
  71 int main(void)
  72 {
  73         struct timex tx;
  74         struct timespec ts;
  75         time_t next_leap;
  76         int count = 0;
  77
  78         setbuf(stdout, NULL);
  79
  80         signal(SIGINT, handler);
  81         signal(SIGKILL, handler);
  82         printf("This runs for a few minutes. Press ctrl-c to stop\n");
  83
  84         clear_time_state();
  85
  86
  87         /* Get the current time */
  88         clock_gettime(CLOCK_REALTIME, &ts);
  89
  90         /* Calculate the next possible leap second 23:59:60 GMT */
  91         next_leap = ts.tv_sec;
  92         next_leap += 86400 - (next_leap % 86400);
  93
  94         for (count = 0; count < 20; count++) {
  95                 struct timeval tv;
  96
  97
  98                 /* set the time to 2 seconds before the leap */
  99                 tv.tv_sec = next_leap - 2;
 100                 tv.tv_usec = 0;
 101                 if (settimeofday(&tv, NULL)) {
 102                         printf("Error: You're likely not running with proper (ie: root) permissions\n");
 103                         return ksft_exit_fail();
 104                 }
 105                 tx.modes = 0;
 106                 adjtimex(&tx);
 107
 108                 /* hammer on adjtime w/ STA_INS */
 109                 while (tx.time.tv_sec < next_leap + 1) {
 110                         /* Set the leap second insert flag */
 111                         tx.modes = ADJ_STATUS;
 112                         tx.status = STA_INS;
 113                         adjtimex(&tx);
 114                 }
 115                 clear_time_state();
 116                 printf(".");
 117         }
 118         printf("[OK]\n");
 119         return ksft_exit_pass();
 120 }