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 }
121