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 }
108