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, 21 insertions, 7 deletions

diff --git a/src/core/unit.c b/src/core/unit.c
index 6e1c112124..b0bb0260bc 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -1704,16 +1704,27 @@ int unit_watch_pid(Unit *u, pid_t pid) {
         assert(u);
         assert(pid >= 1);
 
+        /* Watch a specific PID. We only support one or two units
+         * watching each PID for now, not more. */
+
+        r = hashmap_ensure_allocated(&u->manager->watch_pids1, trivial_hash_func, trivial_compare_func);
+        if (r < 0)
+                return r;
+
         r = set_ensure_allocated(&u->pids, trivial_hash_func, trivial_compare_func);
         if (r < 0)
                 return r;
 
-        /* Watch a specific PID. We only support one unit watching
-         * each PID for now. */
+        r = hashmap_put(u->manager->watch_pids1, LONG_TO_PTR(pid), u);
+        if (r == -EEXIST) {
+                r = hashmap_ensure_allocated(&u->manager->watch_pids2, trivial_hash_func, trivial_compare_func);
+                if (r < 0)
+                        return r;
 
-        r = set_put(u->pids, LONG_TO_PTR(pid));
+                r = hashmap_put(u->manager->watch_pids2, LONG_TO_PTR(pid), u);
+        }
 
-        q = hashmap_put(u->manager->watch_pids, LONG_TO_PTR(pid), u);
+        q = set_put(u->pids, LONG_TO_PTR(pid));
         if (q < 0)
                 return q;
 
@@ -1724,7 +1735,8 @@ void unit_unwatch_pid(Unit *u, pid_t pid) {
         assert(u);
         assert(pid >= 1);
 
-        hashmap_remove_value(u->manager->watch_pids, LONG_TO_PTR(pid), u);
+        hashmap_remove_value(u->manager->watch_pids1, LONG_TO_PTR(pid), u);
+        hashmap_remove_value(u->manager->watch_pids2, LONG_TO_PTR(pid), u);
         set_remove(u->pids, LONG_TO_PTR(pid));
 }
 
@@ -1797,8 +1809,10 @@ void unit_unwatch_all_pids(Unit *u) {
 
         assert(u);
 
-        SET_FOREACH(e, u->pids, i)
-                hashmap_remove_value(u->manager->watch_pids, e, u);
+        SET_FOREACH(e, u->pids, i) {
+                hashmap_remove_value(u->manager->watch_pids1, e, u);
+                hashmap_remove_value(u->manager->watch_pids2, e, u);
+        }
 
         set_free(u->pids);
         u->pids = NULL;