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      1 /* Demo leapsecond deadlock
      2  *              by: John Stultz (john.stultz (at) 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 }
    121