LXR linux/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 */
  28int 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 */
  51void handler(int unused)
  52{
  53        clear_time_state();
  54        exit(0);
  55}
  56
  57
  58int 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                fflush(stdout);
 105        }
 106        printf("[OK]\n");
 107        return ksft_exit_pass();
 108}
 109