leapcrash.c

/* Demo leapsecond deadlock
 *              by: John Stultz (john.stultz@linaro.org)
 *              (C) Copyright IBM 2012
 *              (C) Copyright 2013, 2015 Linaro Limited
 *              Licensed under the GPL
 *
 * This test demonstrates leapsecond deadlock that is possibe
 * on kernels from 2.6.26 to 3.3.
 *
 * WARNING: THIS WILL LIKELY HARDHANG SYSTEMS AND MAY LOSE DATA
 * RUN AT YOUR OWN RISK!
 *  To build:
 *	$ gcc leapcrash.c -o leapcrash -lrt
 */



#include <stdio.h>
#include <stdlib.h>
#include <time.h>
#include <sys/time.h>
#include <sys/timex.h>
#include <string.h>
#include <signal.h>
#ifdef KTEST
#include "../kselftest.h"
#else
static inline int ksft_exit_pass(void)
{
	exit(0);
}
static inline int ksft_exit_fail(void)
{
	exit(1);
}
#endif



/* clear NTP time_status & time_state */
int clear_time_state(void)
{
	struct timex tx;
	int ret;

	/*
	 * We have to call adjtime twice here, as kernels
	 * prior to 6b1859dba01c7 (included in 3.5 and
	 * -stable), had an issue with the state machine
	 * and wouldn't clear the STA_INS/DEL flag directly.
	 */
	tx.modes = ADJ_STATUS;
	tx.status = STA_PLL;
	ret = adjtimex(&tx);

	tx.modes = ADJ_STATUS;
	tx.status = 0;
	ret = adjtimex(&tx);

	return ret;
}

/* Make sure we cleanup on ctrl-c */
void handler(int unused)
{
	clear_time_state();
	exit(0);
}


int main(void)
{
	struct timex tx;
	struct timespec ts;
	time_t next_leap;
	int count = 0;

	setbuf(stdout, NULL);

	signal(SIGINT, handler);
	signal(SIGKILL, handler);
	printf("This runs for a few minutes. Press ctrl-c to stop\n");

	clear_time_state();


	/* Get the current time */
	clock_gettime(CLOCK_REALTIME, &ts);

	/* Calculate the next possible leap second 23:59:60 GMT */
	next_leap = ts.tv_sec;
	next_leap += 86400 - (next_leap % 86400);

	for (count = 0; count < 20; count++) {
		struct timeval tv;


		/* set the time to 2 seconds before the leap */
		tv.tv_sec = next_leap - 2;
		tv.tv_usec = 0;
		if (settimeofday(&tv, NULL)) {
			printf("Error: You're likely not running with proper (ie: root) permissions\n");
			return ksft_exit_fail();
		}
		tx.modes = 0;
		adjtimex(&tx);

		/* hammer on adjtime w/ STA_INS */
		while (tx.time.tv_sec < next_leap + 1) {
			/* Set the leap second insert flag */
			tx.modes = ADJ_STATUS;
			tx.status = STA_INS;
			adjtimex(&tx);
		}
		clear_time_state();
		printf(".");
	}
	printf("[OK]\n");
	return ksft_exit_pass();
}