core: disable event sources before unreffing them

This mirrors the change done for systemd-resolved in
97935302283729c9206b84f5e00b1aff0f78ad19. Quoting that patch:

> We generally operate on the assumption that a source is "gone" as soon as we
> unref it. This is generally true because we have the only reference. But if
> something else holds the reference, our unref doesn't really stop the source
> and it could fire again.

In particular, we take temporary references from sd-event code, and when called
from an sd-event callback, we could temporarily see this elevated reference
count. This patch doesn't seem to change anything, but I think it's nicer to do
the same change as in other places and not rely on _unref() immediately
disabling the source.

1 files changed, 4 insertions, 4 deletions

diff --git a/src/core/timer.c b/src/core/timer.c
index b0caaf3850..e064ad9a2d 100644
--- a/src/core/timer.c
+++ b/src/core/timer.c
@@ -65,8 +65,8 @@ static void timer_done(Unit *u) {
 
         timer_free_values(t);
 
-        t->monotonic_event_source = sd_event_source_unref(t->monotonic_event_source);
-        t->realtime_event_source = sd_event_source_unref(t->realtime_event_source);
+        t->monotonic_event_source = sd_event_source_disable_unref(t->monotonic_event_source);
+        t->realtime_event_source = sd_event_source_disable_unref(t->realtime_event_source);
 
         free(t->stamp_path);
 }
@@ -296,8 +296,8 @@ static void timer_set_state(Timer *t, TimerState state) {
         t->state = state;
 
         if (state != TIMER_WAITING) {
-                t->monotonic_event_source = sd_event_source_unref(t->monotonic_event_source);
-                t->realtime_event_source = sd_event_source_unref(t->realtime_event_source);
+                t->monotonic_event_source = sd_event_source_disable_unref(t->monotonic_event_source);
+                t->realtime_event_source = sd_event_source_disable_unref(t->realtime_event_source);
                 t->next_elapse_monotonic_or_boottime = USEC_INFINITY;
                 t->next_elapse_realtime = USEC_INFINITY;
         }