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 possible
8 * on kernels from 2.6.26 to 3.3.
9 *
10 * WARNING: THIS WILL LIKELY HARD HANG 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