timedate: handle more nicely if something or somebody keeps open /dev/rtc and thus blocks out everybody else

chrony is appears to keep the RTC open continuously these days which is
a bad idea, and /dev/rtc is a single-user device, which is a bad idea
too. Together both bad ideas mean that nobody else can access the RTC
anymore. That's something to fix, but in the meantime we should handle
this more gracefully.

1 files changed, 6 insertions, 4 deletions

diff --git a/src/timedate/timedated.c b/src/timedate/timedated.c
index 809c80bad1..3d450ca3fa 100644
--- a/src/timedate/timedated.c
+++ b/src/timedate/timedated.c
@@ -467,12 +467,14 @@ static int property_get_rtc_time(
 
         zero(tm);
         r = hwclock_get_time(&tm);
-        if (r < 0) {
+        if (r == -EBUSY) {
+                log_warning("/dev/rtc is busy, is somebody keeping it open continously? That's not a good idea... Returning a bogus RTC timestamp.");
+                t = 0;
+        } else if (r < 0) {
                 sd_bus_error_set_errnof(error, -r, "Failed to read RTC: %s", strerror(-r));
                 return r;
-        }
-
-        t = (usec_t) mktime(&tm) * USEC_PER_SEC;
+        } else
+                t = (usec_t) mktime(&tm) * USEC_PER_SEC;
 
         r = sd_bus_message_append(reply, "t", t);
         if (r < 0)