core: allow PIDs to be watched by two units at the same time

In some cases it is interesting to map a PID to two units at the same
time. For example, when a user logs in via a getty, which is reexeced to
/sbin/login that binary will be explicitly referenced as main pid of the
getty service, as well as implicitly referenced as part of the session
scope.

1 files changed, 8 insertions, 1 deletions

diff --git a/src/core/manager.h b/src/core/manager.h
index 358aba7ff9..948ea98a45 100644
--- a/src/core/manager.h
+++ b/src/core/manager.h
@@ -96,7 +96,14 @@ struct Manager {
 
         sd_event *event;
 
-        Hashmap *watch_pids;  /* pid => Unit object n:1 */
+        /* We use two hash tables here, since the same PID might be
+         * watched by two different units: once the unit that forked
+         * it off, and possibly a different unit to which it was
+         * joined as cgroup member. Since we know that it is either
+         * one or two units for each PID we just use to hashmaps
+         * here. */
+        Hashmap *watch_pids1;  /* pid => Unit object n:1 */
+        Hashmap *watch_pids2;  /* pid => Unit object n:1 */
 
         sd_event_source *run_queue_event_source;