core: order timer units after both time-sync.target and time-set.target

If users do not enable a service like systemd-time-wait-sync.target
(because they don't want to delay boot for external events, such as an
NTP sync), then timers should still take the the weaker time-set.target
feature into account, so that the clock is at least monotonic.

Hence, order timer units after both of the targets: time-sync.target
*and* time-set.target. That way, the right thing will happen regardless
if people have no NTP server (and thus also no
systemd-time-wait-sync.service or equivalent) or, only have an NTP
server (and no systemd-time-wait-sync.service), or have both.

Ordering after time-set.target is basically "free". The logic it is
backed by should be instant, without communication with the outside
going on. It's useful still so that time servers that implement the
timestamp from /var/ logic can run in later boot.

diff --git a/src/basic/special.h b/src/basic/special.h
index d55b3289dee184ae97f9e4002e826706c53f6fc3..b9b7be7a7dda98c0b0840bacabcda882c75ed150 100644 (file)
--- a/src/basic/special.h
+++ b/src/basic/special.h
@@ -42,6 +42,7 @@
 #define SPECIAL_SWAP_TARGET "swap.target"
 #define SPECIAL_NETWORK_ONLINE_TARGET "network-online.target"
 #define SPECIAL_TIME_SYNC_TARGET "time-sync.target"       /* LSB's $time */
+#define SPECIAL_TIME_SET_TARGET "time-set.target"
 #define SPECIAL_BASIC_TARGET "basic.target"
 
 /* LSB compatibility */

diff --git a/src/core/timer.c b/src/core/timer.c
index f42c86da765f3e21d4d63d8f3a6fca11bfdb130a..32abdb74d76c52abdff304864da205cd31864dde 100644 (file)
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -99,13 +99,20 @@ static int timer_add_default_dependencies(Timer *t) {
                 if (r < 0)
                         return r;
 
-                LIST_FOREACH(value, v, t->values)
-                        if (v->base == TIMER_CALENDAR) {
-                                r = unit_add_dependency_by_name(UNIT(t), UNIT_AFTER, SPECIAL_TIME_SYNC_TARGET, true, UNIT_DEPENDENCY_DEFAULT);
+                LIST_FOREACH(value, v, t->values) {
+                        const char *target;
+
+                        if (v->base != TIMER_CALENDAR)
+                                continue;
+
+                        FOREACH_STRING(target, SPECIAL_TIME_SYNC_TARGET, SPECIAL_TIME_SET_TARGET) {
+                                r = unit_add_dependency_by_name(UNIT(t), UNIT_AFTER, target, true, UNIT_DEPENDENCY_DEFAULT);
                                 if (r < 0)
                                         return r;
-                                break;
                         }
+
+                        break;
+                }
         }
 
         return unit_add_two_dependencies_by_name(UNIT(t), UNIT_BEFORE, UNIT_CONFLICTS, SPECIAL_SHUTDOWN_TARGET, true, UNIT_DEPENDENCY_DEFAULT);