autofs-5.1.1 - use monotonic clock for alarm thread condition wait

From: Yu Ning <ning.yu@ubuntu.com>

The time returned by gettimeofday() is affected by discontinuous jumps

in the system time, so it causes an issue that autofs may not auto

unmount a mount point if system time is manually changed by the system

administrator.

To fix the issue we need to convert to using a monotonic clock source

instead of the clock source used by gettimeofday().

Convert the alarm_handler() to use a monotonic clock source.

Signed-off-by: Yu Ning <ning.yu@ubuntu.com>

Signed-off-by: Ian Kent <raven@themaw.net>

---

 CHANGELOG   |    1 +

 lib/alarm.c |   28 ++++++++++++++++++++++------

 2 files changed, 23 insertions(+), 6 deletions(-)

diff --git a/CHANGELOG b/CHANGELOG

index 566a6c6..c443f49 100644

--- a/CHANGELOG

+++ b/CHANGELOG

@@ -24,6 +24,7 @@

 - fix error handling of is_mounted().

 - Add a mode option for master map entries.

 - define monotonic clock helper functions.

+- use monotonic clock for alarm thread condition wait.

 21/04/2015 autofs-5.1.1

 =======================

diff --git a/lib/alarm.c b/lib/alarm.c

index 0f04ef8..e6a880b 100755

--- a/lib/alarm.c

+++ b/lib/alarm.c

@@ -23,7 +23,7 @@ struct alarm {

 };

 static pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

-static pthread_cond_t cond = PTHREAD_COND_INITIALIZER;

+static pthread_cond_t cond;

 static LIST_HEAD(alarms);

 #define alarm_lock() \

@@ -46,7 +46,7 @@ int alarm_add(struct autofs_point *ap, time_t seconds)

 	struct list_head *head;

 	struct list_head *p;

 	struct alarm *new;

-	time_t now = time(NULL);

+	time_t now = monotonic_time(NULL);

 	time_t next_alarm = 0;

 	unsigned int empty = 1;

 	int status;

@@ -175,17 +175,18 @@ static void *alarm_handler(void *arg)

 		first = list_entry(head->next, struct alarm, list);

-		now = time(NULL);

+		now = monotonic_time(NULL);

 		if (first->time > now) {

-			struct timeval usecs;

+			struct timespec nsecs;

+

 			/* 

 			 * Wait for alarm to trigger or a new alarm 

 			 * to be added.

 			 */

-			gettimeofday(&usecs, NULL);

+			clock_gettime(CLOCK_MONOTONIC, &nsecs);

 			expire.tv_sec = first->time;

-			expire.tv_nsec = usecs.tv_usec * 1000;

+			expire.tv_nsec = nsecs.tv_nsec;

 			status = pthread_cond_timedwait(&cond, &mutex, &expire);

 			if (status && status != ETIMEDOUT)

@@ -212,6 +213,7 @@ int alarm_start_handler(void)

 	pthread_t thid;

 	pthread_attr_t attrs;

 	pthread_attr_t *pattrs = &attrs;

+	pthread_condattr_t condattrs;

 	int status;

 	status = pthread_attr_init(pattrs);

@@ -224,8 +226,22 @@ int alarm_start_handler(void)

 #endif

 	}

+	status = pthread_condattr_init(&condattrs);

+	if (status)

+		fatal(status);

+

+	status = pthread_condattr_setclock(&condattrs, CLOCK_MONOTONIC);

+	if (status)

+		fatal(status);

+

+	status = pthread_cond_init(&cond, &condattrs);

+	if (status)

+		fatal(status);

+

 	status = pthread_create(&thid, pattrs, alarm_handler, NULL);

+	pthread_condattr_destroy(&condattrs);

+

 	if (pattrs)

 		pthread_attr_destroy(pattrs);