hwclock: always set the kernel's timezone

Properly tell the kernel at bootup, and any later time zone changes,
the actual system time zone.

Things like the kernel's FAT filesystem driver needs the actual time
zone to calculate the proper local time to use for the on-disk time
stamps.

https://bugzilla.redhat.com/show_bug.cgi?id=802198

4 files changed, 26 insertions, 15 deletions

diff --git a/src/core/main.c b/src/core/main.c
index 44c010cfb..199383e63 100644
--- a/src/core/main.c
+++ b/src/core/main.c
@@ -1319,17 +1319,26 @@ int main(int argc, char *argv[]) {
                 if (label_init(NULL) < 0)
                         goto finish;
 
-                if (!skip_setup)
+                if (!skip_setup) {
                         if (hwclock_is_localtime() > 0) {
                                 int min;
 
-                                r = hwclock_apply_localtime_delta(&min);
+                                /* The first-time call to settimeofday() does a time warp in the kernel */
+                                r = hwclock_set_timezone(&min);
                                 if (r < 0)
                                         log_error("Failed to apply local time delta, ignoring: %s", strerror(-r));
                                 else
                                         log_info("RTC configured in localtime, applying delta of %i minutes to system time.", min);
-                        }
+                        } else {
+                                /* Do dummy first-time call to seal the kernel's time warp magic */
+                                hwclock_reset_timezone();
 
+                                /* Tell the kernel our time zone */
+                                r = hwclock_set_timezone(NULL);
+                                if (r < 0)
+                                        log_error("Failed to set the kernel's time zone, ignoring: %s", strerror(-r));
+                        }
+                }
         } else {
                 arg_running_as = MANAGER_USER;
                 log_set_target(LOG_TARGET_AUTO);
diff --git a/src/shared/hwclock.c b/src/shared/hwclock.c
index 9f8ab08e2..d9d5600ff 100644
--- a/src/shared/hwclock.c
+++ b/src/shared/hwclock.c
@@ -188,7 +188,7 @@ int hwclock_is_localtime(void) {
         return local;
 }
 
-int hwclock_apply_localtime_delta(int *min) {
+int hwclock_set_timezone(int *min) {
         const struct timeval *tv_null = NULL;
         struct timespec ts;
         struct tm *tm;
@@ -214,13 +214,18 @@ int hwclock_apply_localtime_delta(int *min) {
         return 0;
 }
 
-int hwclock_reset_localtime_delta(void) {
+int hwclock_reset_timezone(void) {
         const struct timeval *tv_null = NULL;
         struct timezone tz;
 
         tz.tz_minuteswest = 0;
         tz.tz_dsttime = 0; /* DST_NONE*/
 
+        /*
+         * The very first time we set the kernel's timezone, it will warp
+         * the clock. Do a dummy call here, so the time warping is sealed
+         * and we set only the time zone with next call.
+         */
         if (settimeofday(tv_null, &tz) < 0)
                 return -errno;
 
diff --git a/src/shared/hwclock.h b/src/shared/hwclock.h
index 26d1b444e..b2bdc78f0 100644
--- a/src/shared/hwclock.h
+++ b/src/shared/hwclock.h
@@ -23,8 +23,8 @@
 ***/
 
 int hwclock_is_localtime(void);
-int hwclock_apply_localtime_delta(int *min);
-int hwclock_reset_localtime_delta(void);
+int hwclock_set_timezone(int *min);
+int hwclock_reset_timezone(void);
 int hwclock_get_time(struct tm *tm);
 int hwclock_set_time(const struct tm *tm);
 
diff --git a/src/timedate/timedated.c b/src/timedate/timedated.c
index 7eed31c47..0ebece893 100644
--- a/src/timedate/timedated.c
+++ b/src/timedate/timedated.c
@@ -696,13 +696,13 @@ static DBusHandlerResult timedate_message_handler(
                                 return bus_send_error_reply(connection, message, NULL, r);
                         }
 
+                        /* 2. Tell the kernel our time zone */
+                        hwclock_set_timezone(NULL);
+
                         if (tz.local_rtc) {
                                 struct timespec ts;
                                 struct tm *tm;
 
-                                /* 2. Teach kernel new timezone */
-                                hwclock_apply_localtime_delta(NULL);
-
                                 /* 3. Sync RTC from system clock, with the new delta */
                                 assert_se(clock_gettime(CLOCK_REALTIME, &ts) == 0);
                                 assert_se(tm = localtime(&ts.tv_sec));
@@ -753,11 +753,8 @@ static DBusHandlerResult timedate_message_handler(
                                 return bus_send_error_reply(connection, message, NULL, r);
                         }
 
-                        /* 2. Teach kernel new timezone */
-                        if (tz.local_rtc)
-                                hwclock_apply_localtime_delta(NULL);
-                        else
-                                hwclock_reset_localtime_delta();
+                        /* 2. Tell the kernel our time zone */
+                        hwclock_set_timezone(NULL);
 
                         /* 3. Synchronize clocks */
                         assert_se(clock_gettime(CLOCK_REALTIME, &ts) == 0);